The system catalogs are the place where a relational database management system stores schema metadata, such as information about tables and columns, and internal bookkeeping information. PostgreSQL's system catalogs are regular tables. You can drop and recreate the tables, add columns, insert and update values, and severely mess up your system that way. Normally, one should not change the system catalogs by hand, there are always SQL commands to do that. (For example, CREATE DATABASE inserts a row into the pg_database catalog — and actually creates the database on disk.) There are some exceptions for particularly esoteric operations, such as adding index access methods. lists the system catalogs. More detailed documentation of each catalog follows below. Most system catalogs are copied from the template database during database creation and are thereafter database-specific. A few catalogs are physically shared across all databases in a cluster; these are noted in the descriptions of the individual catalogs. Catalog Name Purpose pg_aggregate aggregate functions pg_am index access methods pg_amop access method operators pg_amproc access method support procedures pg_attrdef column default values pg_attribute table columns (attributes) pg_authid authorization identifiers (roles) pg_auth_members authorization identifier membership relationships pg_cast casts (data type conversions) pg_class tables, indexes, sequences, views (relations) pg_collation collations (locale information) pg_constraint check constraints, unique constraints, primary key constraints, foreign key constraints pg_conversion encoding conversion information pg_database databases within this database cluster pg_db_role_setting per-role and per-database settings pg_default_acl default privileges for object types pg_depend dependencies between database objects pg_description descriptions or comments on database objects pg_enum enum label and value definitions pg_event_trigger event triggers pg_extension installed extensions pg_foreign_data_wrapper foreign-data wrapper definitions pg_foreign_server foreign server definitions pg_foreign_table additional foreign table information pg_index additional index information pg_inherits table inheritance hierarchy pg_language languages for writing functions pg_largeobject data pages for large objects pg_largeobject_metadata metadata for large objects pg_namespace schemas pg_opclass access method operator classes pg_operator operators pg_opfamily access method operator families pg_pltemplate template data for procedural languages pg_policy row-security policies pg_proc functions and procedures pg_range information about range types pg_rewrite query rewrite rules pg_replication_origin registered replication origins pg_replication_origin_status information about replication origins, including replication progress pg_replication_slots replication slot information pg_seclabel security labels on database objects pg_shdepend dependencies on shared objects pg_shdescription comments on shared objects pg_shseclabel security labels on shared database objects pg_statistic planner statistics pg_tablesample_method table sampling methods pg_tablespace tablespaces within this database cluster pg_transform transforms (data type to procedural language conversions) pg_trigger triggers pg_ts_config text search configurations pg_ts_config_map text search configurations' token mappings pg_ts_dict text search dictionaries pg_ts_parser text search parsers pg_ts_template text search templates pg_type data types pg_user_mapping mappings of users to foreign servers pg_aggregate The catalog pg_aggregate stores information about aggregate functions. An aggregate function is a function that operates on a set of values (typically one column from each row that matches a query condition) and returns a single value computed from all these values. Typical aggregate functions are sum, count, and max. Each entry in pg_aggregate is an extension of an entry in pg_proc. The pg_proc entry carries the aggregate's name, input and output data types, and other information that is similar to ordinary functions. Name Type References Description aggfnoid regproc pg_proc.oid pg_proc OID of the aggregate function aggkind char Aggregate kind: n for normal aggregates, o for ordered-set aggregates, or h for hypothetical-set aggregates aggnumdirectargs int2 Number of direct (non-aggregated) arguments of an ordered-set or hypothetical-set aggregate, counting a variadic array as one argument. If equal to pronargs, the aggregate must be variadic and the variadic array describes the aggregated arguments as well as the final direct arguments. Always zero for normal aggregates. aggtransfn regproc pg_proc.oid Transition function aggfinalfn regproc pg_proc.oid Final function (zero if none) aggmtransfn regproc pg_proc.oid Forward transition function for moving-aggregate mode (zero if none) aggminvtransfn regproc pg_proc.oid Inverse transition function for moving-aggregate mode (zero if none) aggmfinalfn regproc pg_proc.oid Final function for moving-aggregate mode (zero if none) aggfinalextra bool True to pass extra dummy arguments to aggfinalfn aggmfinalextra bool True to pass extra dummy arguments to aggmfinalfn aggsortop oid pg_operator.oid Associated sort operator (zero if none) aggtranstype oid pg_type.oid Data type of the aggregate function's internal transition (state) data aggtransspace int4 Approximate average size (in bytes) of the transition state data, or zero to use a default estimate aggmtranstype oid pg_type.oid Data type of the aggregate function's internal transition (state) data for moving-aggregate mode (zero if none) aggmtransspace int4 Approximate average size (in bytes) of the transition state data for moving-aggregate mode, or zero to use a default estimate agginitval text The initial value of the transition state. This is a text field containing the initial value in its external string representation. If this field is null, the transition state value starts out null. aggminitval text The initial value of the transition state for moving-aggregate mode. This is a text field containing the initial value in its external string representation. If this field is null, the transition state value starts out null. New aggregate functions are registered with the command. See for more information about writing aggregate functions and the meaning of the transition functions, etc. pg_am The catalog pg_am stores information about index access methods. There is one row for each index access method supported by the system. The contents of this catalog are discussed in detail in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) amname name Name of the access method amstrategies int2 Number of operator strategies for this access method, or zero if access method does not have a fixed set of operator strategies amsupport int2 Number of support routines for this access method amcanorder bool Does the access method support ordered scans sorted by the indexed column's value? amcanorderbyop bool Does the access method support ordered scans sorted by the result of an operator on the indexed column? amcanbackward bool Does the access method support backward scanning? amcanunique bool Does the access method support unique indexes? amcanmulticol bool Does the access method support multicolumn indexes? amoptionalkey bool Does the access method support a scan without any constraint for the first index column? amsearcharray bool Does the access method support ScalarArrayOpExpr searches? amsearchnulls bool Does the access method support IS NULL/NOT NULL searches? amstorage bool Can index storage data type differ from column data type? amclusterable bool Can an index of this type be clustered on? ampredlocks bool Does an index of this type manage fine-grained predicate locks? amkeytype oid pg_type.oid Type of data stored in index, or zero if not a fixed type aminsert regproc pg_proc.oid Insert this tuple function ambeginscan regproc pg_proc.oid Prepare for index scan function amgettuple regproc pg_proc.oid Next valid tuple function, or zero if none amgetbitmap regproc pg_proc.oid Fetch all valid tuples function, or zero if none amrescan regproc pg_proc.oid (Re)start index scan function amendscan regproc pg_proc.oid Clean up after index scan function ammarkpos regproc pg_proc.oid Mark current scan position function amrestrpos regproc pg_proc.oid Restore marked scan position function ambuild regproc pg_proc.oid Build new index function ambuildempty regproc pg_proc.oid Build empty index function ambulkdelete regproc pg_proc.oid Bulk-delete function amvacuumcleanup regproc pg_proc.oid Post-VACUUM cleanup function amcanreturn regproc pg_proc.oid Function to check whether an index column supports index-only scans. Can be zero if index-only scans are never supported. amcostestimate regproc pg_proc.oid Function to estimate cost of an index scan amoptions regproc pg_proc.oid Function to parse and validate reloptions for an index pg_amop The catalog pg_amop stores information about operators associated with access method operator families. There is one row for each operator that is a member of an operator family. A family member can be either a search operator or an ordering operator. An operator can appear in more than one family, but cannot appear in more than one search position nor more than one ordering position within a family. (It is allowed, though unlikely, for an operator to be used for both search and ordering purposes.) Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) amopfamily oid pg_opfamily.oid The operator family this entry is for amoplefttype oid pg_type.oid Left-hand input data type of operator amoprighttype oid pg_type.oid Right-hand input data type of operator amopstrategy int2 Operator strategy number amoppurpose char Operator purpose, either s for search or o for ordering amopopr oid pg_operator.oid OID of the operator amopmethod oid pg_am.oid Index access method operator family is for amopsortfamily oid pg_opfamily.oid The B-tree operator family this entry sorts according to, if an ordering operator; zero if a search operator A search operator entry indicates that an index of this operator family can be searched to find all rows satisfying WHERE indexed_column operator constant. Obviously, such an operator must return boolean, and its left-hand input type must match the index's column data type. An ordering operator entry indicates that an index of this operator family can be scanned to return rows in the order represented by ORDER BY indexed_column operator constant. Such an operator could return any sortable data type, though again its left-hand input type must match the index's column data type. The exact semantics of the ORDER BY are specified by the amopsortfamily column, which must reference a B-tree operator family for the operator's result type. At present, it's assumed that the sort order for an ordering operator is the default for the referenced operator family, i.e., ASC NULLS LAST. This might someday be relaxed by adding additional columns to specify sort options explicitly. An entry's amopmethod must match the opfmethod of its containing operator family (including amopmethod here is an intentional denormalization of the catalog structure for performance reasons). Also, amoplefttype and amoprighttype must match the oprleft and oprright fields of the referenced pg_operator entry. pg_amproc The catalog pg_amproc stores information about support procedures associated with access method operator families. There is one row for each support procedure belonging to an operator family. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) amprocfamily oid pg_opfamily.oid The operator family this entry is for amproclefttype oid pg_type.oid Left-hand input data type of associated operator amprocrighttype oid pg_type.oid Right-hand input data type of associated operator amprocnum int2 Support procedure number amproc regproc pg_proc.oid OID of the procedure The usual interpretation of the amproclefttype and amprocrighttype fields is that they identify the left and right input types of the operator(s) that a particular support procedure supports. For some access methods these match the input data type(s) of the support procedure itself, for others not. There is a notion of default support procedures for an index, which are those with amproclefttype and amprocrighttype both equal to the index operator class's opcintype. pg_attrdef The catalog pg_attrdef stores column default values. The main information about columns is stored in pg_attribute (see below). Only columns that explicitly specify a default value (when the table is created or the column is added) will have an entry here. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) adrelid oid pg_class.oid The table this column belongs to adnum int2 pg_attribute.attnum The number of the column adbin pg_node_tree The internal representation of the column default value adsrc text A human-readable representation of the default value The adsrc field is historical, and is best not used, because it does not track outside changes that might affect the representation of the default value. Reverse-compiling the adbin field (with pg_get_expr for example) is a better way to display the default value. pg_attribute The catalog pg_attribute stores information about table columns. There will be exactly one pg_attribute row for every column in every table in the database. (There will also be attribute entries for indexes, and indeed all objects that have pg_class entries.) The term attribute is equivalent to column and is used for historical reasons. Name Type References Description attrelid oid pg_class.oid The table this column belongs to attname name The column name atttypid oid pg_type.oid The data type of this column attstattarget int4 attstattarget controls the level of detail of statistics accumulated for this column by . A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of most common values to collect, and the target number of histogram bins to create. attlen int2 A copy of pg_type.typlen of this column's type attnum int2 The number of the column. Ordinary columns are numbered from 1 up. System columns, such as oid, have (arbitrary) negative numbers. attndims int4 Number of dimensions, if the column is an array type; otherwise 0. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means it's an array.) attcacheoff int4 Always -1 in storage, but when loaded into a row descriptor in memory this might be updated to cache the offset of the attribute within the row atttypmod int4 atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). It is passed to type-specific input functions and length coercion functions. The value will generally be -1 for types that do not need atttypmod. attbyval bool A copy of pg_type.typbyval of this column's type attstorage char Normally a copy of pg_type.typstorage of this column's type. For TOAST-able data types, this can be altered after column creation to control storage policy. attalign char A copy of pg_type.typalign of this column's type attnotnull bool This represents a not-null constraint. atthasdef bool This column has a default value, in which case there will be a corresponding entry in the pg_attrdef catalog that actually defines the value. attisdropped bool This column has been dropped and is no longer valid. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL. attislocal bool This column is defined locally in the relation. Note that a column can be locally defined and inherited simultaneously. attinhcount int4 The number of direct ancestors this column has. A column with a nonzero number of ancestors cannot be dropped nor renamed. attcollation oid pg_collation.oid The defined collation of the column, or zero if the column is not of a collatable data type. attacl aclitem[] Column-level access privileges, if any have been granted specifically on this column attoptions text[] Attribute-level options, as keyword=value strings attfdwoptions text[] Attribute-level foreign data wrapper options, as keyword=value strings In a dropped column's pg_attribute entry, atttypid is reset to zero, but attlen and the other fields copied from pg_type are still valid. This arrangement is needed to cope with the situation where the dropped column's data type was later dropped, and so there is no pg_type row anymore. attlen and the other fields can be used to interpret the contents of a row of the table. pg_authid The catalog pg_authid contains information about database authorization identifiers (roles). A role subsumes the concepts of users and groups. A user is essentially just a role with the rolcanlogin flag set. Any role (with or without rolcanlogin) can have other roles as members; see pg_auth_members. Since this catalog contains passwords, it must not be publicly readable. pg_roles is a publicly readable view on pg_authid that blanks out the password field. contains detailed information about user and privilege management. Because user identities are cluster-wide, pg_authid is shared across all databases of a cluster: there is only one copy of pg_authid per cluster, not one per database. Name Type Description oid oid Row identifier (hidden attribute; must be explicitly selected) rolname name Role name rolsuper bool Role has superuser privileges rolinherit bool Role automatically inherits privileges of roles it is a member of rolcreaterole bool Role can create more roles rolcreatedb bool Role can create databases rolcanlogin bool Role can log in. That is, this role can be given as the initial session authorization identifier rolreplication bool Role is a replication role. That is, this role can initiate streaming replication (see ) and set/unset the system backup mode using pg_start_backup and pg_stop_backup rolbypassrls bool Role can bypass row level security policies, see for more information. rolconnlimit int4 For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit. rolpassword text Password (possibly encrypted); null if none. If the password is encrypted, this column will begin with the string md5 followed by a 32-character hexadecimal MD5 hash. The MD5 hash will be of the user's password concatenated to their user name. For example, if user joe has password xyzzy, PostgreSQL will store the md5 hash of xyzzyjoe. A password that does not follow that format is assumed to be unencrypted. rolvaliduntil timestamptz Password expiry time (only used for password authentication); null if no expiration pg_auth_members The catalog pg_auth_members shows the membership relations between roles. Any non-circular set of relationships is allowed. Because user identities are cluster-wide, pg_auth_members is shared across all databases of a cluster: there is only one copy of pg_auth_members per cluster, not one per database. Name Type References Description roleid oid pg_authid.oid ID of a role that has a member member oid pg_authid.oid ID of a role that is a member of roleid grantor oid pg_authid.oid ID of the role that granted this membership admin_option bool True if member can grant membership in roleid to others pg_cast The catalog pg_cast stores data type conversion paths, both built-in and user-defined. It should be noted that pg_cast does not represent every type conversion that the system knows how to perform; only those that cannot be deduced from some generic rule. For example, casting between a domain and its base type is not explicitly represented in pg_cast. Another important exception is that automatic I/O conversion casts, those performed using a data type's own I/O functions to convert to or from text or other string types, are not explicitly represented in pg_cast. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) castsource oid pg_type.oid OID of the source data type casttarget oid pg_type.oid OID of the target data type castfunc oid pg_proc.oid The OID of the function to use to perform this cast. Zero is stored if the cast method doesn't require a function. castcontext char Indicates what contexts the cast can be invoked in. e means only as an explicit cast (using CAST or :: syntax). a means implicitly in assignment to a target column, as well as explicitly. i means implicitly in expressions, as well as the other cases. castmethod char Indicates how the cast is performed. f means that the function specified in the castfunc field is used. i means that the input/output functions are used. b means that the types are binary-coercible, thus no conversion is required. The cast functions listed in pg_cast must always take the cast source type as their first argument type, and return the cast destination type as their result type. A cast function can have up to three arguments. The second argument, if present, must be type integer; it receives the type modifier associated with the destination type, or -1 if there is none. The third argument, if present, must be type boolean; it receives true if the cast is an explicit cast, false otherwise. It is legitimate to create a pg_cast entry in which the source and target types are the same, if the associated function takes more than one argument. Such entries represent length coercion functions that coerce values of the type to be legal for a particular type modifier value. When a pg_cast entry has different source and target types and a function that takes more than one argument, it represents converting from one type to another and applying a length coercion in a single step. When no such entry is available, coercion to a type that uses a type modifier involves two steps, one to convert between data types and a second to apply the modifier. pg_class The catalog pg_class catalogs tables and most everything else that has columns or is otherwise similar to a table. This includes indexes (but see also pg_index), sequences, views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of relations. Not all columns are meaningful for all relation types. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) relname name Name of the table, index, view, etc. relnamespace oid pg_namespace.oid The OID of the namespace that contains this relation reltype oid pg_type.oid The OID of the data type that corresponds to this table's row type, if any (zero for indexes, which have no pg_type entry) reloftype oid pg_type.oid For typed tables, the OID of the underlying composite type, zero for all other relations relowner oid pg_authid.oid Owner of the relation relam oid pg_am.oid If this is an index, the access method used (B-tree, hash, etc.) relfilenode oid Name of the on-disk file of this relation; zero means this is a mapped relation whose disk file name is determined by low-level state reltablespace oid pg_tablespace.oid The tablespace in which this relation is stored. If zero, the database's default tablespace is implied. (Not meaningful if the relation has no on-disk file.) relpages int4 Size of the on-disk representation of this table in pages (of size BLCKSZ). This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. reltuples float4 Number of rows in the table. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. relallvisible int4 Number of pages that are marked all-visible in the table's visibility map. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. reltoastrelid oid pg_class.oid OID of the TOAST table associated with this table, 0 if none. The TOAST table stores large attributes out of line in a secondary table. relhasindex bool True if this is a table and it has (or recently had) any indexes relisshared bool True if this table is shared across all databases in the cluster. Only certain system catalogs (such as pg_database) are shared. relpersistence char p = permanent table, u = unlogged table, t = temporary table relkind char r = ordinary table, i = index, S = sequence, v = view, m = materialized view, c = composite type, t = TOAST table, f = foreign table relnatts int2 Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in pg_attribute. See also pg_attribute.attnum. relchecks int2 Number of CHECK constraints on the table; see pg_constraint catalog relhasoids bool True if we generate an OID for each row of the relation relhaspkey bool True if the table has (or once had) a primary key relhasrules bool True if table has (or once had) rules; see pg_rewrite catalog relhastriggers bool True if table has (or once had) triggers; see pg_trigger catalog relhassubclass bool True if table has (or once had) any inheritance children relrowsecurity bool True if table has row level security enabled; see pg_policy catalog relispopulated bool True if relation is populated (this is true for all relations other than some materialized views) relreplident char Columns used to form replica identity for rows: d = default (primary key, if any), n = nothing, f = all columns i = index with indisreplident set, or default relfrozenxid xid All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk. Zero (InvalidTransactionId) if the relation is not a table. relminmxid xid All multitransaction IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multitransaction ID ID wraparound or to allow pg_clog to be shrunk. Zero (InvalidTransactionId) if the relation is not a table. relacl aclitem[] Access privileges; see and for details reloptions text[] Access-method-specific options, as keyword=value strings Several of the Boolean flags in pg_class are maintained lazily: they are guaranteed to be true if that's the correct state, but may not be reset to false immediately when the condition is no longer true. For example, relhasindex is set by CREATE INDEX, but it is never cleared by DROP INDEX. Instead, VACUUM clears relhasindex if it finds the table has no indexes. This arrangement avoids race conditions and improves concurrency. pg_collation The catalog pg_collation describes the available collations, which are essentially mappings from an SQL name to operating system locale categories. See for more information. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) collname name Collation name (unique per namespace and encoding) collnamespace oid pg_namespace.oid The OID of the namespace that contains this collation collowner oid pg_authid.oid Owner of the collation collencoding int4 Encoding in which the collation is applicable, or -1 if it works for any encoding collcollate name LC_COLLATE for this collation object collctype name LC_CTYPE for this collation object Note that the unique key on this catalog is (collname, collencoding, collnamespace) not just (collname, collnamespace). PostgreSQL generally ignores all collations that do not have collencoding equal to either the current database's encoding or -1, and creation of new entries with the same name as an entry with collencoding = -1 is forbidden. Therefore it is sufficient to use a qualified SQL name (schema.name) to identify a collation, even though this is not unique according to the catalog definition. The reason for defining the catalog this way is that initdb fills it in at cluster initialization time with entries for all locales available on the system, so it must be able to hold entries for all encodings that might ever be used in the cluster. In the template0 database, it could be useful to create collations whose encoding does not match the database encoding, since they could match the encodings of databases later cloned from template0. This would currently have to be done manually. pg_constraint The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables. (Column constraints are not treated specially. Every column constraint is equivalent to some table constraint.) Not-null constraints are represented in the pg_attribute catalog, not here. User-defined constraint triggers (created with CREATE CONSTRAINT TRIGGER) also give rise to an entry in this table. Check constraints on domains are stored here, too. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) conname name Constraint name (not necessarily unique!) connamespace oid pg_namespace.oid The OID of the namespace that contains this constraint contype char c = check constraint, f = foreign key constraint, p = primary key constraint, u = unique constraint, t = constraint trigger, x = exclusion constraint condeferrable bool Is the constraint deferrable? condeferred bool Is the constraint deferred by default? convalidated bool Has the constraint been validated? Currently, can only be false for foreign keys and CHECK constraints conrelid oid pg_class.oid The table this constraint is on; 0 if not a table constraint contypid oid pg_type.oid The domain this constraint is on; 0 if not a domain constraint conindid oid pg_class.oid The index supporting this constraint, if it's a unique, primary key, foreign key, or exclusion constraint; else 0 confrelid oid pg_class.oid If a foreign key, the referenced table; else 0 confupdtype char Foreign key update action code: a = no action, r = restrict, c = cascade, n = set null, d = set default confdeltype char Foreign key deletion action code: a = no action, r = restrict, c = cascade, n = set null, d = set default confmatchtype char Foreign key match type: f = full, p = partial, s = simple conislocal bool This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously. coninhcount int4 The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed. connoinherit bool This constraint is defined locally for the relation. It is a non-inheritable constraint. conkey int2[] pg_attribute.attnum If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns confkey int2[] pg_attribute.attnum If a foreign key, list of the referenced columns conpfeqop oid[] pg_operator.oid If a foreign key, list of the equality operators for PK = FK comparisons conppeqop oid[] pg_operator.oid If a foreign key, list of the equality operators for PK = PK comparisons conffeqop oid[] pg_operator.oid If a foreign key, list of the equality operators for FK = FK comparisons conexclop oid[] pg_operator.oid If an exclusion constraint, list of the per-column exclusion operators conbin pg_node_tree If a check constraint, an internal representation of the expression consrc text If a check constraint, a human-readable representation of the expression In the case of an exclusion constraint, conkey is only useful for constraint elements that are simple column references. For other cases, a zero appears in conkey and the associated index must be consulted to discover the expression that is constrained. (conkey thus has the same contents as pg_index.indkey for the index.) consrc is not updated when referenced objects change; for example, it won't track renaming of columns. Rather than relying on this field, it's best to use pg_get_constraintdef() to extract the definition of a check constraint. pg_class.relchecks needs to agree with the number of check-constraint entries found in this table for each relation. pg_conversion The catalog pg_conversion describes encoding conversion procedures. See for more information. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) conname name Conversion name (unique within a namespace) connamespace oid pg_namespace.oid The OID of the namespace that contains this conversion conowner oid pg_authid.oid Owner of the conversion conforencoding int4 Source encoding ID contoencoding int4 Destination encoding ID conproc regproc pg_proc.oid Conversion procedure condefault bool True if this is the default conversion pg_database The catalog pg_database stores information about the available databases. Databases are created with the command. Consult for details about the meaning of some of the parameters. Unlike most system catalogs, pg_database is shared across all databases of a cluster: there is only one copy of pg_database per cluster, not one per database. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) datname name Database name datdba oid pg_authid.oid Owner of the database, usually the user who created it encoding int4 Character encoding for this database (pg_encoding_to_char() can translate this number to the encoding name) datcollate name LC_COLLATE for this database datctype name LC_CTYPE for this database datistemplate bool If true, then this database can be cloned by any user with CREATEDB privileges; if false, then only superusers or the owner of the database can clone it. datallowconn bool If false then no one can connect to this database. This is used to protect the template0 database from being altered. datconnlimit int4 Sets maximum number of concurrent connections that can be made to this database. -1 means no limit. datlastsysoid oid Last system OID in the database; useful particularly to pg_dump datfrozenxid xid All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk. It is the minimum of the per-table pg_class.relfrozenxid values. datminmxid xid All multitransaction IDs before this one have been replaced with a transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk. It is the minimum of the per-table pg_class.relminmxid values. dattablespace oid pg_tablespace.oid The default tablespace for the database. Within this database, all tables for which pg_class.reltablespace is zero will be stored in this tablespace; in particular, all the non-shared system catalogs will be there. datacl aclitem[] Access privileges; see and for details pg_db_role_setting The catalog pg_db_role_setting records the default values that have been set for run-time configuration variables, for each role and database combination. Unlike most system catalogs, pg_db_role_setting is shared across all databases of a cluster: there is only one copy of pg_db_role_setting per cluster, not one per database. Name Type References Description setdatabase oid pg_database.oid The OID of the database the setting is applicable to, or zero if not database-specific setrole oid pg_authid.oid The OID of the role the setting is applicable to, or zero if not role-specific setconfig text[] Defaults for run-time configuration variables pg_default_acl The catalog pg_default_acl stores initial privileges to be assigned to newly created objects. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) defaclrole oid pg_authid.oid The OID of the role associated with this entry defaclnamespace oid pg_namespace.oid The OID of the namespace associated with this entry, or 0 if none defaclobjtype char Type of object this entry is for: r = relation (table, view), S = sequence, f = function, T = type defaclacl aclitem[] Access privileges that this type of object should have on creation A pg_default_acl entry shows the initial privileges to be assigned to an object belonging to the indicated user. There are currently two types of entry: global entries with defaclnamespace = 0, and per-schema entries that reference a particular schema. If a global entry is present then it overrides the normal hard-wired default privileges for the object type. A per-schema entry, if present, represents privileges to be added to the global or hard-wired default privileges. Note that when an ACL entry in another catalog is null, it is taken to represent the hard-wired default privileges for its object, not whatever might be in pg_default_acl at the moment. pg_default_acl is only consulted during object creation. pg_depend The catalog pg_depend records the dependency relationships between database objects. This information allows DROP commands to find which other objects must be dropped by DROP CASCADE or prevent dropping in the DROP RESTRICT case. See also pg_shdepend, which performs a similar function for dependencies involving objects that are shared across a database cluster. Name Type References Description classid oid pg_class.oid The OID of the system catalog the dependent object is in objid oid any OID column The OID of the specific dependent object objsubid int4 For a table column, this is the column number (the objid and classid refer to the table itself). For all other object types, this column is zero. refclassid oid pg_class.oid The OID of the system catalog the referenced object is in refobjid oid any OID column The OID of the specific referenced object refobjsubid int4 For a table column, this is the column number (the refobjid and refclassid refer to the table itself). For all other object types, this column is zero. deptype char A code defining the specific semantics of this dependency relationship; see text In all cases, a pg_depend entry indicates that the referenced object cannot be dropped without also dropping the dependent object. However, there are several subflavors identified by deptype: DEPENDENCY_NORMAL (n) A normal relationship between separately-created objects. The dependent object can be dropped without affecting the referenced object. The referenced object can only be dropped by specifying CASCADE, in which case the dependent object is dropped, too. Example: a table column has a normal dependency on its data type. DEPENDENCY_AUTO (a) The dependent object can be dropped separately from the referenced object, and should be automatically dropped (regardless of RESTRICT or CASCADE mode) if the referenced object is dropped. Example: a named constraint on a table is made autodependent on the table, so that it will go away if the table is dropped. DEPENDENCY_INTERNAL (i) The dependent object was created as part of creation of the referenced object, and is really just a part of its internal implementation. A DROP of the dependent object will be disallowed outright (we'll tell the user to issue a DROP against the referenced object, instead). A DROP of the referenced object will be propagated through to drop the dependent object whether CASCADE is specified or not. Example: a trigger that's created to enforce a foreign-key constraint is made internally dependent on the constraint's pg_constraint entry. DEPENDENCY_EXTENSION (e) The dependent object is a member of the extension that is the referenced object (see pg_extension). The dependent object can be dropped only via DROP EXTENSION on the referenced object. Functionally this dependency type acts the same as an internal dependency, but it's kept separate for clarity and to simplify pg_dump. DEPENDENCY_PIN (p) There is no dependent object; this type of entry is a signal that the system itself depends on the referenced object, and so that object must never be deleted. Entries of this type are created only by initdb. The columns for the dependent object contain zeroes. Other dependency flavors might be needed in future. pg_description The catalog pg_description stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the command and viewed with psql's \d commands. Descriptions of many built-in system objects are provided in the initial contents of pg_description. See also pg_shdescription, which performs a similar function for descriptions involving objects that are shared across a database cluster. Name Type References Description objoid oid any OID column The OID of the object this description pertains to classoid oid pg_class.oid The OID of the system catalog this object appears in objsubid int4 For a comment on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero. description text Arbitrary text that serves as the description of this object pg_enum The pg_enum catalog contains entries showing the values and labels for each enum type. The internal representation of a given enum value is actually the OID of its associated row in pg_enum. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) enumtypid oid pg_type.oid The OID of the pg_type entry owning this enum value enumsortorder float4 The sort position of this enum value within its enum type enumlabel name The textual label for this enum value The OIDs for pg_enum rows follow a special rule: even-numbered OIDs are guaranteed to be ordered in the same way as the sort ordering of their enum type. That is, if two even OIDs belong to the same enum type, the smaller OID must have the smaller enumsortorder value. Odd-numbered OID values need bear no relationship to the sort order. This rule allows the enum comparison routines to avoid catalog lookups in many common cases. The routines that create and alter enum types attempt to assign even OIDs to enum values whenever possible. When an enum type is created, its members are assigned sort-order positions 1..n. But members added later might be given negative or fractional values of enumsortorder. The only requirement on these values is that they be correctly ordered and unique within each enum type. pg_event_trigger The catalog pg_event_trigger stores event triggers. See for more information. Name Type References Description evtname name Trigger name (must be unique) evtevent name Identifies the event for which this trigger fires evtowner oid pg_authid.oid Owner of the event trigger evtfoid oid pg_proc.oid The function to be called evtenabled char Controls in which modes the event trigger fires. O = trigger fires in origin and local modes, D = trigger is disabled, R = trigger fires in replica mode, A = trigger fires always. evttags text[] Command tags for which this trigger will fire. If NULL, the firing of this trigger is not restricted on the basis of the command tag. pg_extension The catalog pg_extension stores information about the installed extensions. See for details about extensions. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) extname name Name of the extension extowner oid pg_authid.oid Owner of the extension extnamespace oid pg_namespace.oid Schema containing the extension's exported objects extrelocatable bool True if extension can be relocated to another schema extversion text Version name for the extension extconfig oid[] pg_class.oid Array of regclass OIDs for the extension's configuration table(s), or NULL if none extcondition text[] Array of WHERE-clause filter conditions for the extension's configuration table(s), or NULL if none Note that unlike most catalogs with a namespace column, extnamespace is not meant to imply that the extension belongs to that schema. Extension names are never schema-qualified. Rather, extnamespace indicates the schema that contains most or all of the extension's objects. If extrelocatable is true, then this schema must in fact contain all schema-qualifiable objects belonging to the extension. pg_foreign_data_wrapper The catalog pg_foreign_data_wrapper stores foreign-data wrapper definitions. A foreign-data wrapper is the mechanism by which external data, residing on foreign servers, is accessed. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) fdwname name Name of the foreign-data wrapper fdwowner oid pg_authid.oid Owner of the foreign-data wrapper fdwhandler oid pg_proc.oid References a handler function that is responsible for supplying execution routines for the foreign-data wrapper. Zero if no handler is provided fdwvalidator oid pg_proc.oid References a validator function that is responsible for checking the validity of the options given to the foreign-data wrapper, as well as options for foreign servers and user mappings using the foreign-data wrapper. Zero if no validator is provided fdwacl aclitem[] Access privileges; see and for details fdwoptions text[] Foreign-data wrapper specific options, as keyword=value strings pg_foreign_server The catalog pg_foreign_server stores foreign server definitions. A foreign server describes a source of external data, such as a remote server. Foreign servers are accessed via foreign-data wrappers. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) srvname name Name of the foreign server srvowner oid pg_authid.oid Owner of the foreign server srvfdw oid pg_foreign_data_wrapper.oid OID of the foreign-data wrapper of this foreign server srvtype text Type of the server (optional) srvversion text Version of the server (optional) srvacl aclitem[] Access privileges; see and for details srvoptions text[] Foreign server specific options, as keyword=value strings pg_foreign_table The catalog pg_foreign_table contains auxiliary information about foreign tables. A foreign table is primarily represented by a pg_class entry, just like a regular table. Its pg_foreign_table entry contains the information that is pertinent only to foreign tables and not any other kind of relation. Name Type References Description ftrelid oid pg_class.oid OID of the pg_class entry for this foreign table ftserver oid pg_foreign_server.oid OID of the foreign server for this foreign table ftoptions text[] Foreign table options, as keyword=value strings pg_index The catalog pg_index contains part of the information about indexes. The rest is mostly in pg_class. Name Type References Description indexrelid oid pg_class.oid The OID of the pg_class entry for this index indrelid oid pg_class.oid The OID of the pg_class entry for the table this index is for indnatts int2 The number of columns in the index (duplicates pg_class.relnatts) indisunique bool If true, this is a unique index indisprimary bool If true, this index represents the primary key of the table (indisunique should always be true when this is true) indisexclusion bool If true, this index supports an exclusion constraint indimmediate bool If true, the uniqueness check is enforced immediately on insertion (irrelevant if indisunique is not true) indisclustered bool If true, the table was last clustered on this index indisvalid bool If true, the index is currently valid for queries. False means the index is possibly incomplete: it must still be modified by INSERT/UPDATE operations, but it cannot safely be used for queries. If it is unique, the uniqueness property is not guaranteed true either. indcheckxmin bool If true, queries must not use the index until the xmin of this pg_index row is below their TransactionXmin event horizon, because the table may contain broken HOT chains with incompatible rows that they can see indisready bool If true, the index is currently ready for inserts. False means the index must be ignored by INSERT/UPDATE operations. indislive bool If false, the index is in process of being dropped, and should be ignored for all purposes (including HOT-safety decisions) indisreplident bool If true this index has been chosen as replica identity using ALTER TABLE ... REPLICA IDENTITY USING INDEX ... indkey int2vector pg_attribute.attnum This is an array of indnatts values that indicate which table columns this index indexes. For example a value of 1 3 would mean that the first and the third table columns make up the index key. A zero in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference. indcollation oidvector pg_collation.oid For each column in the index key, this contains the OID of the collation to use for the index. indclass oidvector pg_opclass.oid For each column in the index key, this contains the OID of the operator class to use. See pg_opclass for details. indoption int2vector This is an array of indnatts values that store per-column flag bits. The meaning of the bits is defined by the index's access method. indexprs pg_node_tree Expression trees (in nodeToString() representation) for index attributes that are not simple column references. This is a list with one element for each zero entry in indkey. Null if all index attributes are simple references. indpred pg_node_tree Expression tree (in nodeToString() representation) for partial index predicate. Null if not a partial index. pg_inherits The catalog pg_inherits records information about table inheritance hierarchies. There is one entry for each direct child table in the database. (Indirect inheritance can be determined by following chains of entries.) Name Type References Description inhrelid oid pg_class.oid The OID of the child table inhparent oid pg_class.oid The OID of the parent table inhseqno int4 If there is more than one direct parent for a child table (multiple inheritance), this number tells the order in which the inherited columns are to be arranged. The count starts at 1. pg_language The catalog pg_language registers languages in which you can write functions or stored procedures. See and for more information about language handlers. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) lanname name Name of the language lanowner oid pg_authid.oid Owner of the language lanispl bool This is false for internal languages (such as SQL) and true for user-defined languages. Currently, pg_dump still uses this to determine which languages need to be dumped, but this might be replaced by a different mechanism in the future. lanpltrusted bool True if this is a trusted language, which means that it is believed not to grant access to anything outside the normal SQL execution environment. Only superusers can create functions in untrusted languages. lanplcallfoid oid pg_proc.oid For noninternal languages this references the language handler, which is a special function that is responsible for executing all functions that are written in the particular language laninline oid pg_proc.oid This references a function that is responsible for executing inline anonymous code blocks ( blocks). Zero if inline blocks are not supported. lanvalidator oid pg_proc.oid This references a language validator function that is responsible for checking the syntax and validity of new functions when they are created. Zero if no validator is provided. lanacl aclitem[] Access privileges; see and for details pg_largeobject The catalog pg_largeobject holds the data making up large objects. A large object is identified by an OID assigned when it is created. Each large object is broken into segments or pages small enough to be conveniently stored as rows in pg_largeobject. The amount of data per page is defined to be LOBLKSIZE (which is currently BLCKSZ/4, or typically 2 kB). Prior to PostgreSQL 9.0, there was no permission structure associated with large objects. As a result, pg_largeobject was publicly readable and could be used to obtain the OIDs (and contents) of all large objects in the system. This is no longer the case; use pg_largeobject_metadata to obtain a list of large object OIDs. Name Type References Description loid oid pg_largeobject_metadata.oid Identifier of the large object that includes this page pageno int4 Page number of this page within its large object (counting from zero) data bytea Actual data stored in the large object. This will never be more than LOBLKSIZE bytes and might be less. Each row of pg_largeobject holds data for one page of a large object, beginning at byte offset (pageno * LOBLKSIZE) within the object. The implementation allows sparse storage: pages might be missing, and might be shorter than LOBLKSIZE bytes even if they are not the last page of the object. Missing regions within a large object read as zeroes. pg_largeobject_metadata The catalog pg_largeobject_metadata holds metadata associated with large objects. The actual large object data is stored in pg_largeobject. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) lomowner oid pg_authid.oid Owner of the large object lomacl aclitem[] Access privileges; see and for details pg_namespace The catalog pg_namespace stores namespaces. A namespace is the structure underlying SQL schemas: each namespace can have a separate collection of relations, types, etc. without name conflicts. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) nspname name Name of the namespace nspowner oid pg_authid.oid Owner of the namespace nspacl aclitem[] Access privileges; see and for details pg_opclass The catalog pg_opclass defines index access method operator classes. Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column's data type as their left-hand input. Operator classes are described at length in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) opcmethod oid pg_am.oid Index access method operator class is for opcname name Name of this operator class opcnamespace oid pg_namespace.oid Namespace of this operator class opcowner oid pg_authid.oid Owner of the operator class opcfamily oid pg_opfamily.oid Operator family containing the operator class opcintype oid pg_type.oid Data type that the operator class indexes opcdefault bool True if this operator class is the default for opcintype opckeytype oid pg_type.oid Type of data stored in index, or zero if same as opcintype An operator class's opcmethod must match the opfmethod of its containing operator family. Also, there must be no more than one pg_opclass row having opcdefault true for any given combination of opcmethod and opcintype. pg_operator The catalog pg_operator stores information about operators. See and for more information. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) oprname name Name of the operator oprnamespace oid pg_namespace.oid The OID of the namespace that contains this operator oprowner oid pg_authid.oid Owner of the operator oprkind char b = infix (both), l = prefix (left), r = postfix (right) oprcanmerge bool This operator supports merge joins oprcanhash bool This operator supports hash joins oprleft oid pg_type.oid Type of the left operand oprright oid pg_type.oid Type of the right operand oprresult oid pg_type.oid Type of the result oprcom oid pg_operator.oid Commutator of this operator, if any oprnegate oid pg_operator.oid Negator of this operator, if any oprcode regproc pg_proc.oid Function that implements this operator oprrest regproc pg_proc.oid Restriction selectivity estimation function for this operator oprjoin regproc pg_proc.oid Join selectivity estimation function for this operator Unused column contain zeroes. For example, oprleft is zero for a prefix operator. pg_opfamily The catalog pg_opfamily defines operator families. Each operator family is a collection of operators and associated support routines that implement the semantics specified for a particular index access method. Furthermore, the operators in a family are all compatible, in a way that is specified by the access method. The operator family concept allows cross-data-type operators to be used with indexes and to be reasoned about using knowledge of access method semantics. Operator families are described at length in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) opfmethod oid pg_am.oid Index access method operator family is for opfname name Name of this operator family opfnamespace oid pg_namespace.oid Namespace of this operator family opfowner oid pg_authid.oid Owner of the operator family The majority of the information defining an operator family is not in its pg_opfamily row, but in the associated rows in pg_amop, pg_amproc, and pg_opclass. pg_pltemplate The catalog pg_pltemplate stores template information for procedural languages. A template for a language allows the language to be created in a particular database by a simple CREATE LANGUAGE command, with no need to specify implementation details. Unlike most system catalogs, pg_pltemplate is shared across all databases of a cluster: there is only one copy of pg_pltemplate per cluster, not one per database. This allows the information to be accessible in each database as it is needed. Name Type Description tmplname name Name of the language this template is for tmpltrusted boolean True if language is considered trusted tmpldbacreate boolean True if language may be created by a database owner tmplhandler text Name of call handler function tmplinline text Name of anonymous-block handler function, or null if none tmplvalidator text Name of validator function, or null if none tmpllibrary text Path of shared library that implements language tmplacl aclitem[] Access privileges for template (not actually used) There are not currently any commands that manipulate procedural language templates; to change the built-in information, a superuser must modify the table using ordinary INSERT, DELETE, or UPDATE commands. It is likely that pg_pltemplate will be removed in some future release of PostgreSQL, in favor of keeping this knowledge about procedural languages in their respective extension installation scripts. pg_policy The catalog pg_policy stores row level security policies for tables. A policy includes the kind of command that it applies to (possibly all commands), the roles that it applies to, the expression to be added as a security-barrier qualification to queries that include the table, and the expression to be added as a WITH CHECK option for queries that attempt to add new records to the table. Name Type References Description polname name The name of the policy polrelid oid pg_class.oid The table to which the policy applies polcmd char The command type to which the policy is applied: r for SELECT, a for INSERT, w for UPDATE, d for DELETE, or * for all polroles oid[] pg_authid.oid The roles to which the policy is applied polqual pg_node_tree The expression tree to be added to the security barrier qualifications for queries that use the table polwithcheck pg_node_tree The expression tree to be added to the WITH CHECK qualifications for queries that attempt to add rows to the table Policies stored in pg_policy are applied only when pg_class.relrowsecurity is set for their table. pg_proc The catalog pg_proc stores information about functions (or procedures). See and for more information. The table contains data for aggregate functions as well as plain functions. If proisagg is true, there should be a matching row in pg_aggregate. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) proname name Name of the function pronamespace oid pg_namespace.oid The OID of the namespace that contains this function proowner oid pg_authid.oid Owner of the function prolang oid pg_language.oid Implementation language or call interface of this function procost float4 Estimated execution cost (in units of ); if proretset, this is cost per row returned prorows float4 Estimated number of result rows (zero if not proretset) provariadic oid pg_type.oid Data type of the variadic array parameter's elements, or zero if the function does not have a variadic parameter protransform regproc pg_proc.oid Calls to this function can be simplified by this other function (see ) proisagg bool Function is an aggregate function proiswindow bool Function is a window function prosecdef bool Function is a security definer (i.e., a setuid function) proleakproof bool The function has no side effects. No information about the arguments is conveyed except via the return value. Any function that might throw an error depending on the values of its arguments is not leak-proof. proisstrict bool Function returns null if any call argument is null. In that case the function won't actually be called at all. Functions that are not strict must be prepared to handle null inputs. proretset bool Function returns a set (i.e., multiple values of the specified data type) provolatile char provolatile tells whether the function's result depends only on its input arguments, or is affected by outside factors. It is i for immutable functions, which always deliver the same result for the same inputs. It is s for stable functions, whose results (for fixed inputs) do not change within a scan. It is v for volatile functions, whose results might change at any time. (Use v also for functions with side-effects, so that calls to them cannot get optimized away.) pronargs int2 Number of input arguments pronargdefaults int2 Number of arguments that have defaults prorettype oid pg_type.oid Data type of the return value proargtypes oidvector pg_type.oid An array with the data types of the function arguments. This includes only input arguments (including INOUT and VARIADIC arguments), and thus represents the call signature of the function. proallargtypes oid[] pg_type.oid An array with the data types of the function arguments. This includes all arguments (including OUT and INOUT arguments); however, if all the arguments are IN arguments, this field will be null. Note that subscripting is 1-based, whereas for historical reasons proargtypes is subscripted from 0. proargmodes char[] An array with the modes of the function arguments, encoded as i for IN arguments, o for OUT arguments, b for INOUT arguments, v for VARIADIC arguments, t for TABLE arguments. If all the arguments are IN arguments, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes. proargnames text[] An array with the names of the function arguments. Arguments without a name are set to empty strings in the array. If none of the arguments have a name, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes. proargdefaults pg_node_tree Expression trees (in nodeToString() representation) for default values. This is a list with pronargdefaults elements, corresponding to the last N input arguments (i.e., the last N proargtypes positions). If none of the arguments have defaults, this field will be null. protrftypes oid[] Data type OIDs for which to apply transforms. prosrc text This tells the function handler how to invoke the function. It might be the actual source code of the function for interpreted languages, a link symbol, a file name, or just about anything else, depending on the implementation language/call convention. probin text Additional information about how to invoke the function. Again, the interpretation is language-specific. proconfig text[] Function's local settings for run-time configuration variables proacl aclitem[] Access privileges; see and for details For compiled functions, both built-in and dynamically loaded, prosrc contains the function's C-language name (link symbol). For all other currently-known language types, prosrc contains the function's source text. probin is unused except for dynamically-loaded C functions, for which it gives the name of the shared library file containing the function. pg_range The catalog pg_range stores information about range types. This is in addition to the types' entries in pg_type. Name Type References Description rngtypid oid pg_type.oid OID of the range type rngsubtype oid pg_type.oid OID of the element type (subtype) of this range type rngcollation oid pg_collation.oid OID of the collation used for range comparisons, or 0 if none rngsubopc oid pg_opclass.oid OID of the subtype's operator class used for range comparisons rngcanonical regproc pg_proc.oid OID of the function to convert a range value into canonical form, or 0 if none rngsubdiff regproc pg_proc.oid OID of the function to return the difference between two element values as double precision, or 0 if none rngsubopc (plus rngcollation, if the element type is collatable) determines the sort ordering used by the range type. rngcanonical is used when the element type is discrete. rngsubdiff is optional but should be supplied to improve performance of GiST indexes on the range type. pg_rewrite The catalog pg_rewrite stores rewrite rules for tables and views. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) rulename name Rule name ev_class oid pg_class.oid The table this rule is for ev_type char Event type that the rule is for: 1 = SELECT, 2 = UPDATE, 3 = INSERT, 4 = DELETE ev_enabled char Controls in which modes the rule fires. O = rule fires in origin and local modes, D = rule is disabled, R = rule fires in replica mode, A = rule fires always. is_instead bool True if the rule is an INSTEAD rule ev_qual pg_node_tree Expression tree (in the form of a nodeToString() representation) for the rule's qualifying condition ev_action pg_node_tree Query tree (in the form of a nodeToString() representation) for the rule's action pg_class.relhasrules must be true if a table has any rules in this catalog. pg_replication_origin The pg_replication_origin catalog contains all replication origins created. For more on replication origins see . Name Type References Description roident Oid A unique, cluster-wide identifier for the replication origin. Should never leave the system. roname text The external, user defined, name of a replication origin. pg_replication_origin_status The pg_replication_origin_status view contains information about how far replay for a certain origin has progressed. For more on replication origins see . Name Type References Description local_id Oid pg_replication_origin.roident internal node identifier external_id text pg_replication_origin.roname external node identifier remote_lsn pg_lsn The origin node's LSN up to which data has been replicated. local_lsn pg_lsn This node's LSN that at which remote_lsn has been replicated. Used to flush commit records before persisting data to disk when using asynchronous commits. pg_replication_slots The pg_replication_slots view provides a listing of all replication slots that currently exist on the database cluster, along with their current state. For more on replication slots, see and . Name Type References Description slot_name name A unique, cluster-wide identifier for the replication slot plugin name The base name of the shared object containing the output plugin this logical slot is using, or null for physical slots. slot_type text The slot type - physical or logical datoid oid pg_database.oid The OID of the database this slot is associated with, or null. Only logical slots have an associated database. database text pg_database.datname The name of the database this slot is associated with, or null. Only logical slots have an associated database. active boolean True if this slot is currently actively being used active_pid integer The process ID of the session using this slot if the slot is currently actively being used. NULL if inactive. xmin xid The oldest transaction that this slot needs the database to retain. VACUUM cannot remove tuples deleted by any later transaction. catalog_xmin xid The oldest transaction affecting the system catalogs that this slot needs the database to retain. VACUUM cannot remove catalog tuples deleted by any later transaction. restart_lsn pg_lsn The address (LSN) of oldest WAL which still might be required by the consumer of this slot and thus won't be automatically removed during checkpoints. pg_seclabel The catalog pg_seclabel stores security labels on database objects. Security labels can be manipulated with the command. For an easier way to view security labels, see . See also pg_shseclabel, which performs a similar function for security labels of database objects that are shared across a database cluster. Name Type References Description objoid oid any OID column The OID of the object this security label pertains to classoid oid pg_class.oid The OID of the system catalog this object appears in objsubid int4 For a security label on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero. provider text The label provider associated with this label. label text The security label applied to this object. pg_shdepend The catalog pg_shdepend records the dependency relationships between database objects and shared objects, such as roles. This information allows PostgreSQL to ensure that those objects are unreferenced before attempting to delete them. See also pg_depend, which performs a similar function for dependencies involving objects within a single database. Unlike most system catalogs, pg_shdepend is shared across all databases of a cluster: there is only one copy of pg_shdepend per cluster, not one per database. Name Type References Description dbid oid pg_database.oid The OID of the database the dependent object is in, or zero for a shared object classid oid pg_class.oid The OID of the system catalog the dependent object is in objid oid any OID column The OID of the specific dependent object objsubid int4 For a table column, this is the column number (the objid and classid refer to the table itself). For all other object types, this column is zero. refclassid oid pg_class.oid The OID of the system catalog the referenced object is in (must be a shared catalog) refobjid oid any OID column The OID of the specific referenced object deptype char A code defining the specific semantics of this dependency relationship; see text In all cases, a pg_shdepend entry indicates that the referenced object cannot be dropped without also dropping the dependent object. However, there are several subflavors identified by deptype: SHARED_DEPENDENCY_OWNER (o) The referenced object (which must be a role) is the owner of the dependent object. SHARED_DEPENDENCY_ACL (a) The referenced object (which must be a role) is mentioned in the ACL (access control list, i.e., privileges list) of the dependent object. (A SHARED_DEPENDENCY_ACL entry is not made for the owner of the object, since the owner will have a SHARED_DEPENDENCY_OWNER entry anyway.) SHARED_DEPENDENCY_PIN (p) There is no dependent object; this type of entry is a signal that the system itself depends on the referenced object, and so that object must never be deleted. Entries of this type are created only by initdb. The columns for the dependent object contain zeroes. Other dependency flavors might be needed in future. Note in particular that the current definition only supports roles as referenced objects. pg_shdescription The catalog pg_shdescription stores optional descriptions (comments) for shared database objects. Descriptions can be manipulated with the command and viewed with psql's \d commands. See also pg_description, which performs a similar function for descriptions involving objects within a single database. Unlike most system catalogs, pg_shdescription is shared across all databases of a cluster: there is only one copy of pg_shdescription per cluster, not one per database. Name Type References Description objoid oid any OID column The OID of the object this description pertains to classoid oid pg_class.oid The OID of the system catalog this object appears in description text Arbitrary text that serves as the description of this object pg_shseclabel The catalog pg_shseclabel stores security labels on shared database objects. Security labels can be manipulated with the command. For an easier way to view security labels, see . See also pg_seclabel, which performs a similar function for security labels involving objects within a single database. Unlike most system catalogs, pg_shseclabel is shared across all databases of a cluster: there is only one copy of pg_shseclabel per cluster, not one per database. Name Type References Description objoid oid any OID column The OID of the object this security label pertains to classoid oid pg_class.oid The OID of the system catalog this object appears in provider text The label provider associated with this label. label text The security label applied to this object. pg_statistic The catalog pg_statistic stores statistical data about the contents of the database. Entries are created by and subsequently used by the query planner. Note that all the statistical data is inherently approximate, even assuming that it is up-to-date. Normally there is one entry, with stainherit = false, for each table column that has been analyzed. If the table has inheritance children, a second entry with stainherit = true is also created. This row represents the column's statistics over the inheritance tree, i.e., statistics for the data you'd see with SELECT column FROM table*, whereas the stainherit = false row represents the results of SELECT column FROM ONLY table. pg_statistic also stores statistical data about the values of index expressions. These are described as if they were actual data columns; in particular, starelid references the index. No entry is made for an ordinary non-expression index column, however, since it would be redundant with the entry for the underlying table column. Currently, entries for index expressions always have stainherit = false. Since different kinds of statistics might be appropriate for different kinds of data, pg_statistic is designed not to assume very much about what sort of statistics it stores. Only extremely general statistics (such as nullness) are given dedicated columns in pg_statistic. Everything else is stored in slots, which are groups of associated columns whose content is identified by a code number in one of the slot's columns. For more information see src/include/catalog/pg_statistic.h. pg_statistic should not be readable by the public, since even statistical information about a table's contents might be considered sensitive. (Example: minimum and maximum values of a salary column might be quite interesting.) pg_stats is a publicly readable view on pg_statistic that only exposes information about those tables that are readable by the current user. Name Type References Description starelid oid pg_class.oid The table or index that the described column belongs to staattnum int2 pg_attribute.attnum The number of the described column stainherit bool If true, the stats include inheritance child columns, not just the values in the specified relation stanullfrac float4 The fraction of the column's entries that are null stawidth int4 The average stored width, in bytes, of nonnull entries stadistinct float4 The number of distinct nonnull data values in the column. A value greater than zero is the actual number of distinct values. A value less than zero is the negative of a multiplier for the number of rows in the table; for example, a column in which values appear about twice on the average could be represented by stadistinct = -0.5. A zero value means the number of distinct values is unknown. stakindN int2 A code number indicating the kind of statistics stored in the Nth slot of the pg_statistic row. staopN oid pg_operator.oid An operator used to derive the statistics stored in the Nth slot. For example, a histogram slot would show the < operator that defines the sort order of the data. stanumbersN float4[] Numerical statistics of the appropriate kind for the Nth slot, or null if the slot kind does not involve numerical values stavaluesN anyarray Column data values of the appropriate kind for the Nth slot, or null if the slot kind does not store any data values. Each array's element values are actually of the specific column's data type, or a related type such as an array's element type, so there is no way to define these columns' type more specifically than anyarray. pg_am The catalog pg_tablesample_method stores information about table sampling methods which can be used in TABLESAMPLE clause of a SELECT statement. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) tsmname name Name of the sampling method tsmseqscan bool If true, the sampling method scans the whole table sequentially. tsmpagemode bool If true, the sampling method always reads the pages completely. tsminit regproc pg_proc.oid Initialize the sampling scan function tsmnextblock regproc pg_proc.oid Get next block number function tsmnexttuple regproc pg_proc.oid Get next tuple offset function tsmexaminetuple regproc pg_proc.oid Function which examines the tuple contents and decides if to return it, or zero if none tsmend regproc pg_proc.oid End the sampling scan function tsmreset regproc pg_proc.oid Restart the state of sampling scan function tsmcost regproc pg_proc.oid Costing function pg_tablespace The catalog pg_tablespace stores information about the available tablespaces. Tables can be placed in particular tablespaces to aid administration of disk layout. Unlike most system catalogs, pg_tablespace is shared across all databases of a cluster: there is only one copy of pg_tablespace per cluster, not one per database. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) spcname name Tablespace name spcowner oid pg_authid.oid Owner of the tablespace, usually the user who created it spcacl aclitem[] Access privileges; see and for details spcoptions text[] Tablespace-level options, as keyword=value strings pg_transform The catalog pg_transform stores information about transforms, which are a mechanism to adapt data types to procedural languages. See for more information. Name Type References Description trftype oid pg_type.oid OID of the data type this transform is for trflang oid pg_language.oid OID of the language this transform is for trffromsql regproc pg_proc.oid The OID of the function to use when converting the data type for input to the procedural language (e.g., function parameters). Zero is stored if this operation is not supported. trftosql regproc pg_proc.oid The OID of the function to use when converting output from the procedural language (e.g., return values) to the data type. Zero is stored if this operation is not supported. pg_trigger The catalog pg_trigger stores triggers on tables and views. See for more information. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) tgrelid oid pg_class.oid The table this trigger is on tgname name Trigger name (must be unique among triggers of same table) tgfoid oid pg_proc.oid The function to be called tgtype int2 Bit mask identifying trigger firing conditions tgenabled char Controls in which modes the trigger fires. O = trigger fires in origin and local modes, D = trigger is disabled, R = trigger fires in replica mode, A = trigger fires always. tgisinternal bool True if trigger is internally generated (usually, to enforce the constraint identified by tgconstraint) tgconstrrelid oid pg_class.oid The table referenced by a referential integrity constraint tgconstrindid oid pg_class.oid The index supporting a unique, primary key, referential integrity, or exclusion constraint tgconstraint oid pg_constraint.oid The pg_constraint entry associated with the trigger, if any tgdeferrable bool True if constraint trigger is deferrable tginitdeferred bool True if constraint trigger is initially deferred tgnargs int2 Number of argument strings passed to trigger function tgattr int2vector pg_attribute.attnum Column numbers, if trigger is column-specific; otherwise an empty array tgargs bytea Argument strings to pass to trigger, each NULL-terminated tgqual pg_node_tree Expression tree (in nodeToString() representation) for the trigger's WHEN condition, or null if none Currently, column-specific triggering is supported only for UPDATE events, and so tgattr is relevant only for that event type. tgtype might contain bits for other event types as well, but those are presumed to be table-wide regardless of what is in tgattr. When tgconstraint is nonzero, tgconstrrelid, tgconstrindid, tgdeferrable, and tginitdeferred are largely redundant with the referenced pg_constraint entry. However, it is possible for a non-deferrable trigger to be associated with a deferrable constraint: foreign key constraints can have some deferrable and some non-deferrable triggers. pg_class.relhastriggers must be true if a relation has any triggers in this catalog. pg_ts_config The pg_ts_config catalog contains entries representing text search configurations. A configuration specifies a particular text search parser and a list of dictionaries to use for each of the parser's output token types. The parser is shown in the pg_ts_config entry, but the token-to-dictionary mapping is defined by subsidiary entries in pg_ts_config_map. PostgreSQL's text search features are described at length in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) cfgname name Text search configuration name cfgnamespace oid pg_namespace.oid The OID of the namespace that contains this configuration cfgowner oid pg_authid.oid Owner of the configuration cfgparser oid pg_ts_parser.oid The OID of the text search parser for this configuration pg_ts_config_map The pg_ts_config_map catalog contains entries showing which text search dictionaries should be consulted, and in what order, for each output token type of each text search configuration's parser. PostgreSQL's text search features are described at length in . Name Type References Description mapcfg oid pg_ts_config.oid The OID of the pg_ts_config entry owning this map entry maptokentype integer A token type emitted by the configuration's parser mapseqno integer Order in which to consult this entry (lower mapseqnos first) mapdict oid pg_ts_dict.oid The OID of the text search dictionary to consult pg_ts_dict The pg_ts_dict catalog contains entries defining text search dictionaries. A dictionary depends on a text search template, which specifies all the implementation functions needed; the dictionary itself provides values for the user-settable parameters supported by the template. This division of labor allows dictionaries to be created by unprivileged users. The parameters are specified by a text string dictinitoption, whose format and meaning vary depending on the template. PostgreSQL's text search features are described at length in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) dictname name Text search dictionary name dictnamespace oid pg_namespace.oid The OID of the namespace that contains this dictionary dictowner oid pg_authid.oid Owner of the dictionary dicttemplate oid pg_ts_template.oid The OID of the text search template for this dictionary dictinitoption text Initialization option string for the template pg_ts_parser The pg_ts_parser catalog contains entries defining text search parsers. A parser is responsible for splitting input text into lexemes and assigning a token type to each lexeme. Since a parser must be implemented by C-language-level functions, creation of new parsers is restricted to database superusers. PostgreSQL's text search features are described at length in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) prsname name Text search parser name prsnamespace oid pg_namespace.oid The OID of the namespace that contains this parser prsstart regproc pg_proc.oid OID of the parser's startup function prstoken regproc pg_proc.oid OID of the parser's next-token function prsend regproc pg_proc.oid OID of the parser's shutdown function prsheadline regproc pg_proc.oid OID of the parser's headline function prslextype regproc pg_proc.oid OID of the parser's lextype function pg_ts_template The pg_ts_template catalog contains entries defining text search templates. A template is the implementation skeleton for a class of text search dictionaries. Since a template must be implemented by C-language-level functions, creation of new templates is restricted to database superusers. PostgreSQL's text search features are described at length in . Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) tmplname name Text search template name tmplnamespace oid pg_namespace.oid The OID of the namespace that contains this template tmplinit regproc pg_proc.oid OID of the template's initialization function tmpllexize regproc pg_proc.oid OID of the template's lexize function pg_type The catalog pg_type stores information about data types. Base types and enum types (scalar types) are created with , and domains with . A composite type is automatically created for each table in the database, to represent the row structure of the table. It is also possible to create composite types with CREATE TYPE AS. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) typname name Data type name typnamespace oid pg_namespace.oid The OID of the namespace that contains this type typowner oid pg_authid.oid Owner of the type typlen int2 For a fixed-size type, typlen is the number of bytes in the internal representation of the type. But for a variable-length type, typlen is negative. -1 indicates a varlena type (one that has a length word), -2 indicates a null-terminated C string. typbyval bool typbyval determines whether internal routines pass a value of this type by value or by reference. typbyval had better be false if typlen is not 1, 2, or 4 (or 8 on machines where Datum is 8 bytes). Variable-length types are always passed by reference. Note that typbyval can be false even if the length would allow pass-by-value. typtype char typtype is b for a base type, c for a composite type (e.g., a table's row type), d for a domain, e for an enum type, p for a pseudo-type, or r for a range type. See also typrelid and typbasetype. typcategory char typcategory is an arbitrary classification of data types that is used by the parser to determine which implicit casts should be preferred. See . typispreferred bool True if the type is a preferred cast target within its typcategory typisdefined bool True if the type is defined, false if this is a placeholder entry for a not-yet-defined type. When typisdefined is false, nothing except the type name, namespace, and OID can be relied on. typdelim char Character that separates two values of this type when parsing array input. Note that the delimiter is associated with the array element data type, not the array data type. typrelid oid pg_class.oid If this is a composite type (see typtype), then this column points to the pg_class entry that defines the corresponding table. (For a free-standing composite type, the pg_class entry doesn't really represent a table, but it is needed anyway for the type's pg_attribute entries to link to.) Zero for non-composite types. typelem oid pg_type.oid If typelem is not 0 then it identifies another row in pg_type. The current type can then be subscripted like an array yielding values of type typelem. A true array type is variable length (typlen = -1), but some fixed-length (typlen > 0) types also have nonzero typelem, for example name and point. If a fixed-length type has a typelem then its internal representation must be some number of values of the typelem data type with no other data. Variable-length array types have a header defined by the array subroutines. typarray oid pg_type.oid If typarray is not 0 then it identifies another row in pg_type, which is the true array type having this type as element typinput regproc pg_proc.oid Input conversion function (text format) typoutput regproc pg_proc.oid Output conversion function (text format) typreceive regproc pg_proc.oid Input conversion function (binary format), or 0 if none typsend regproc pg_proc.oid Output conversion function (binary format), or 0 if none typmodin regproc pg_proc.oid Type modifier input function, or 0 if type does not support modifiers typmodout regproc pg_proc.oid Type modifier output function, or 0 to use the standard format typanalyze regproc pg_proc.oid Custom ANALYZE function, or 0 to use the standard function typalign char typalign is the alignment required when storing a value of this type. It applies to storage on disk as well as most representations of the value inside PostgreSQL. When multiple values are stored consecutively, such as in the representation of a complete row on disk, padding is inserted before a datum of this type so that it begins on the specified boundary. The alignment reference is the beginning of the first datum in the sequence. Possible values are: c = char alignment, i.e., no alignment needed. s = short alignment (2 bytes on most machines). i = int alignment (4 bytes on most machines). d = double alignment (8 bytes on many machines, but by no means all). For types used in system tables, it is critical that the size and alignment defined in pg_type agree with the way that the compiler will lay out the column in a structure representing a table row. typstorage char typstorage tells for varlena types (those with typlen = -1) if the type is prepared for toasting and what the default strategy for attributes of this type should be. Possible values are p: Value must always be stored plain. e: Value can be stored in a secondary relation (if relation has one, see pg_class.reltoastrelid). m: Value can be stored compressed inline. x: Value can be stored compressed inline or stored in secondary storage. Note that m columns can also be moved out to secondary storage, but only as a last resort (e and x columns are moved first). typnotnull bool typnotnull represents a not-null constraint on a type. Used for domains only. typbasetype oid pg_type.oid If this is a domain (see typtype), then typbasetype identifies the type that this one is based on. Zero if this type is not a domain. typtypmod int4 Domains use typtypmod to record the typmod to be applied to their base type (-1 if base type does not use a typmod). -1 if this type is not a domain. typndims int4 typndims is the number of array dimensions for a domain over an array (that is, typbasetype is an array type). Zero for types other than domains over array types. typcollation oid pg_collation.oid typcollation specifies the collation of the type. If the type does not support collations, this will be zero. A base type that supports collations will have DEFAULT_COLLATION_OID here. A domain over a collatable type can have some other collation OID, if one was specified for the domain. typdefaultbin pg_node_tree If typdefaultbin is not null, it is the nodeToString() representation of a default expression for the type. This is only used for domains. typdefault text typdefault is null if the type has no associated default value. If typdefaultbin is not null, typdefault must contain a human-readable version of the default expression represented by typdefaultbin. If typdefaultbin is null and typdefault is not, then typdefault is the external representation of the type's default value, which can be fed to the type's input converter to produce a constant. typacl aclitem[] Access privileges; see and for details lists the system-defined values of typcategory. Any future additions to this list will also be upper-case ASCII letters. All other ASCII characters are reserved for user-defined categories. Code Category A Array types B Boolean types C Composite types D Date/time types E Enum types G Geometric types I Network address types N Numeric types P Pseudo-types R Range types S String types T Timespan types U User-defined types V Bit-string types X unknown type pg_user_mapping The catalog pg_user_mapping stores the mappings from local user to remote. Access to this catalog is restricted from normal users, use the view pg_user_mappings instead. Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) umuser oid pg_authid.oid OID of the local role being mapped, 0 if the user mapping is public umserver oid pg_foreign_server.oid The OID of the foreign server that contains this mapping umoptions text[] User mapping specific options, as keyword=value strings In addition to the system catalogs, PostgreSQL provides a number of built-in views. Some system views provide convenient access to some commonly used queries on the system catalogs. Other views provide access to internal server state. The information schema () provides an alternative set of views which overlap the functionality of the system views. Since the information schema is SQL-standard whereas the views described here are PostgreSQL-specific, it's usually better to use the information schema if it provides all the information you need. lists the system views described here. More detailed documentation of each view follows below. There are some additional views that provide access to the results of the statistics collector; they are described in . Except where noted, all the views described here are read-only. View Name Purpose pg_available_extensions available extensions pg_available_extension_versions available versions of extensions pg_cursors open cursors pg_group groups of database users pg_indexes indexes pg_locks currently held locks pg_matviews materialized views pg_policies policies pg_prepared_statements prepared statements pg_prepared_xacts prepared transactions pg_roles database roles pg_rules rules pg_seclabels security labels pg_settings parameter settings pg_file_settings file location of parameter settings pg_shadow database users pg_stats planner statistics pg_tables tables pg_timezone_abbrevs time zone abbreviations pg_timezone_names time zone names pg_user database users pg_user_mappings user mappings pg_views views pg_available_extensions The pg_available_extensions view lists the extensions that are available for installation. See also the pg_extension catalog, which shows the extensions currently installed. Name Type Description name name Extension name default_version text Name of default version, or NULL if none is specified installed_version text Currently installed version of the extension, or NULL if not installed comment text Comment string from the extension's control file The pg_available_extensions view is read only. pg_available_extension_versions The pg_available_extension_versions view lists the specific extension versions that are available for installation. See also the pg_extension catalog, which shows the extensions currently installed. Name Type Description name name Extension name version text Version name installed bool True if this version of this extension is currently installed superuser bool True if only superusers are allowed to install this extension relocatable bool True if extension can be relocated to another schema schema name Name of the schema that the extension must be installed into, or NULL if partially or fully relocatable requires name[] Names of prerequisite extensions, or NULL if none comment text Comment string from the extension's control file The pg_available_extension_versions view is read only. pg_cursors The pg_cursors view lists the cursors that are currently available. Cursors can be defined in several ways: via the statement in SQL via the Bind message in the frontend/backend protocol, as described in via the Server Programming Interface (SPI), as described in The pg_cursors view displays cursors created by any of these means. Cursors only exist for the duration of the transaction that defines them, unless they have been declared WITH HOLD. Therefore non-holdable cursors are only present in the view until the end of their creating transaction. Cursors are used internally to implement some of the components of PostgreSQL, such as procedural languages. Therefore, the pg_cursors view might include cursors that have not been explicitly created by the user. Name Type Description name text The name of the cursor statement text The verbatim query string submitted to declare this cursor is_holdable boolean true if the cursor is holdable (that is, it can be accessed after the transaction that declared the cursor has committed); false otherwise is_binary boolean true if the cursor was declared BINARY; false otherwise is_scrollable boolean true if the cursor is scrollable (that is, it allows rows to be retrieved in a nonsequential manner); false otherwise creation_time timestamptz The time at which the cursor was declared The pg_cursors view is read only. pg_group The view pg_group exists for backwards compatibility: it emulates a catalog that existed in PostgreSQL before version 8.1. It shows the names and members of all roles that are marked as not rolcanlogin, which is an approximation to the set of roles that are being used as groups. Name Type References Description groname name pg_authid.rolname Name of the group grosysid oid pg_authid.oid ID of this group grolist oid[] pg_authid.oid An array containing the IDs of the roles in this group pg_indexes The view pg_indexes provides access to useful information about each index in the database. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing table and index tablename name pg_class.relname Name of table the index is for indexname name pg_class.relname Name of index tablespace name pg_tablespace.spcname Name of tablespace containing index (null if default for database) indexdef text Index definition (a reconstructed CREATE INDEX command) pg_locks The view pg_locks provides access to information about the locks held by open transactions within the database server. See for more discussion of locking. pg_locks contains one row per active lockable object, requested lock mode, and relevant transaction. Thus, the same lockable object might appear many times, if multiple transactions are holding or waiting for locks on it. However, an object that currently has no locks on it will not appear at all. There are several distinct types of lockable objects: whole relations (e.g., tables), individual pages of relations, individual tuples of relations, transaction IDs (both virtual and permanent IDs), and general database objects (identified by class OID and object OID, in the same way as in pg_description or pg_depend). Also, the right to extend a relation is represented as a separate lockable object. Also, advisory locks can be taken on numbers that have user-defined meanings. Name Type References Description locktype text Type of the lockable object: relation, extend, page, tuple, transactionid, virtualxid, object, userlock, or advisory database oid pg_database.oid OID of the database in which the lock target exists, or zero if the target is a shared object, or null if the target is a transaction ID relation oid pg_class.oid OID of the relation targeted by the lock, or null if the target is not a relation or part of a relation page integer Page number targeted by the lock within the relation, or null if the target is not a relation page or tuple tuple smallint Tuple number targeted by the lock within the page, or null if the target is not a tuple virtualxid text Virtual ID of the transaction targeted by the lock, or null if the target is not a virtual transaction ID transactionid xid ID of the transaction targeted by the lock, or null if the target is not a transaction ID classid oid pg_class.oid OID of the system catalog containing the lock target, or null if the target is not a general database object objid oid any OID column OID of the lock target within its system catalog, or null if the target is not a general database object objsubid smallint Column number targeted by the lock (the classid and objid refer to the table itself), or zero if the target is some other general database object, or null if the target is not a general database object virtualtransaction text Virtual ID of the transaction that is holding or awaiting this lock pid integer Process ID of the server process holding or awaiting this lock, or null if the lock is held by a prepared transaction mode text Name of the lock mode held or desired by this process (see and ) granted boolean True if lock is held, false if lock is awaited fastpath boolean True if lock was taken via fast path, false if taken via main lock table granted is true in a row representing a lock held by the indicated transaction. False indicates that this transaction is currently waiting to acquire this lock, which implies that some other transaction is holding a conflicting lock mode on the same lockable object. The waiting transaction will sleep until the other lock is released (or a deadlock situation is detected). A single transaction can be waiting to acquire at most one lock at a time. Every transaction holds an exclusive lock on its virtual transaction ID for its entire duration. If a permanent ID is assigned to the transaction (which normally happens only if the transaction changes the state of the database), it also holds an exclusive lock on its permanent transaction ID until it ends. When one transaction finds it necessary to wait specifically for another transaction, it does so by attempting to acquire share lock on the other transaction ID (either virtual or permanent ID depending on the situation). That will succeed only when the other transaction terminates and releases its locks. Although tuples are a lockable type of object, information about row-level locks is stored on disk, not in memory, and therefore row-level locks normally do not appear in this view. If a transaction is waiting for a row-level lock, it will usually appear in the view as waiting for the permanent transaction ID of the current holder of that row lock. Advisory locks can be acquired on keys consisting of either a single bigint value or two integer values. A bigint key is displayed with its high-order half in the classid column, its low-order half in the objid column, and objsubid equal to 1. The original bigint value can be reassembled with the expression (classid::bigint << 32) | objid::bigint. Integer keys are displayed with the first key in the classid column, the second key in the objid column, and objsubid equal to 2. The actual meaning of the keys is up to the user. Advisory locks are local to each database, so the database column is meaningful for an advisory lock. pg_locks provides a global view of all locks in the database cluster, not only those relevant to the current database. Although its relation column can be joined against pg_class.oid to identify locked relations, this will only work correctly for relations in the current database (those for which the database column is either the current database's OID or zero). The pid column can be joined to the pid column of the pg_stat_activity view to get more information on the session holding or waiting to hold each lock, for example SELECT * FROM pg_locks pl LEFT JOIN pg_stat_activity psa ON pl.pid = psa.pid; Also, if you are using prepared transactions, the virtualtransaction column can be joined to the transaction column of the pg_prepared_xacts view to get more information on prepared transactions that hold locks. (A prepared transaction can never be waiting for a lock, but it continues to hold the locks it acquired while running.) For example: SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx ON pl.virtualtransaction = '-1/' || ppx.transaction; The pg_locks view displays data from both the regular lock manager and the predicate lock manager, which are separate systems; in addition, the regular lock manager subdivides its locks into regular and fast-path locks. This data is not guaranteed to be entirely consistent. When the view is queried, data on fast-path locks (with fastpath = true) is gathered from each backend one at a time, without freezing the state of the entire lock manager, so it is possible for locks to be taken or released while information is gathered. Note, however, that these locks are known not to conflict with any other lock currently in place. After all backends have been queried for fast-path locks, the remainder of the regular lock manager is locked as a unit, and a consistent snapshot of all remaining locks is collected as an atomic action. After unlocking the regular lock manager, the predicate lock manager is similarly locked and all predicate locks are collected as an atomic action. Thus, with the exception of fast-path locks, each lock manager will deliver a consistent set of results, but as we do not lock both lock managers simultaneously, it is possible for locks to be taken or released after we interrogate the regular lock manager and before we interrogate the predicate lock manager. Locking the regular and/or predicate lock manager could have some impact on database performance if this view is very frequently accessed. The locks are held only for the minimum amount of time necessary to obtain data from the lock managers, but this does not completely eliminate the possibility of a performance impact. pg_matviews materialized views The view pg_matviews provides access to useful information about each materialized view in the database. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing materialized view matviewname name pg_class.relname Name of materialized view matviewowner name pg_authid.rolname Name of materialized view's owner tablespace name pg_tablespace.spcname Name of tablespace containing materialized view (null if default for database) hasindexes boolean True if materialized view has (or recently had) any indexes ispopulated boolean True if materialized view is currently populated definition text Materialized view definition (a reconstructed SELECT query) pg_policies The view pg_policies provides access to useful information about each row-level security policy in the database. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing table policy is on tablename name pg_class.relname Name of table policy is on policyname name pg_policy.polname Name of policy roles name[] The roles to which this policy applies cmd text The command type to which the policy is applied qual text The expression added to the security barrier qualifications for queries that this policy applies to with_check text The expression added to the WITH CHECK qualifications for queries that attempt to add rows to this table pg_prepared_statements The pg_prepared_statements view displays all the prepared statements that are available in the current session. See for more information about prepared statements. pg_prepared_statements contains one row for each prepared statement. Rows are added to the view when a new prepared statement is created and removed when a prepared statement is released (for example, via the command). Name Type Description name text The identifier of the prepared statement statement text The query string submitted by the client to create this prepared statement. For prepared statements created via SQL, this is the PREPARE statement submitted by the client. For prepared statements created via the frontend/backend protocol, this is the text of the prepared statement itself. prepare_time timestamptz The time at which the prepared statement was created parameter_types regtype[] The expected parameter types for the prepared statement in the form of an array of regtype. The OID corresponding to an element of this array can be obtained by casting the regtype value to oid. from_sql boolean true if the prepared statement was created via the PREPARE SQL statement; false if the statement was prepared via the frontend/backend protocol The pg_prepared_statements view is read only. pg_prepared_xacts The view pg_prepared_xacts displays information about transactions that are currently prepared for two-phase commit (see for details). pg_prepared_xacts contains one row per prepared transaction. An entry is removed when the transaction is committed or rolled back. Name Type References Description transaction xid Numeric transaction identifier of the prepared transaction gid text Global transaction identifier that was assigned to the transaction prepared timestamp with time zone Time at which the transaction was prepared for commit owner name pg_authid.rolname Name of the user that executed the transaction database name pg_database.datname Name of the database in which the transaction was executed When the pg_prepared_xacts view is accessed, the internal transaction manager data structures are momentarily locked, and a copy is made for the view to display. This ensures that the view produces a consistent set of results, while not blocking normal operations longer than necessary. Nonetheless there could be some impact on database performance if this view is frequently accessed. pg_roles The view pg_roles provides access to information about database roles. This is simply a publicly readable view of pg_authid that blanks out the password field. This view explicitly exposes the OID column of the underlying table, since that is needed to do joins to other catalogs. Name Type References Description rolname name Role name rolsuper bool Role has superuser privileges rolinherit bool Role automatically inherits privileges of roles it is a member of rolcreaterole bool Role can create more roles rolcreatedb bool Role can create databases rolcanlogin bool Role can log in. That is, this role can be given as the initial session authorization identifier rolreplication bool Role is a replication role. That is, this role can initiate streaming replication (see ) and set/unset the system backup mode using pg_start_backup and pg_stop_backup rolconnlimit int4 For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit. rolpassword text Not the password (always reads as ********) rolvaliduntil timestamptz Password expiry time (only used for password authentication); null if no expiration rolconfig text[] Role-specific defaults for run-time configuration variables oid oid pg_authid.oid ID of role pg_rules The view pg_rules provides access to useful information about query rewrite rules. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing table tablename name pg_class.relname Name of table the rule is for rulename name pg_rewrite.rulename Name of rule definition text Rule definition (a reconstructed creation command) The pg_rules view excludes the ON SELECT rules of views and materialized views; those can be seen in pg_views and pg_matviews. pg_seclabels The view pg_seclabels provides information about security labels. It as an easier-to-query version of the pg_seclabel catalog. Name Type References Description objoid oid any OID column The OID of the object this security label pertains to classoid oid pg_class.oid The OID of the system catalog this object appears in objsubid int4 For a security label on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero. objtype text The type of object to which this label applies, as text. objnamespace oid pg_namespace.oid The OID of the namespace for this object, if applicable; otherwise NULL. objname text The name of the object to which this label applies, as text. provider text pg_seclabel.provider The label provider associated with this label. label text pg_seclabel.label The security label applied to this object. pg_settings The view pg_settings provides access to run-time parameters of the server. It is essentially an alternative interface to the and commands. It also provides access to some facts about each parameter that are not directly available from SHOW, such as minimum and maximum values. Name Type Description name text Run-time configuration parameter name setting text Current value of the parameter unit text Implicit unit of the parameter category text Logical group of the parameter short_desc text A brief description of the parameter extra_desc text Additional, more detailed, description of the parameter context text Context required to set the parameter's value (see below) vartype text Parameter type (bool, enum, integer, real, or string) source text Source of the current parameter value min_val text Minimum allowed value of the parameter (null for non-numeric values) max_val text Maximum allowed value of the parameter (null for non-numeric values) enumvals text[] Allowed values of an enum parameter (null for non-enum values) boot_val text Parameter value assumed at server startup if the parameter is not otherwise set reset_val text Value that RESET would reset the parameter to in the current session sourcefile text Configuration file the current value was set in (null for values set from sources other than configuration files, or when examined by a non-superuser); helpful when using include directives in configuration files sourceline integer Line number within the configuration file the current value was set at (null for values set from sources other than configuration files, or when examined by a non-superuser) pending_restart boolean true if the value has been changed in the configuration file but needs a restart; or false otherwise. There are several possible values of context. In order of decreasing difficulty of changing the setting, they are: internal These settings cannot be changed directly; they reflect internally determined values. Some of them may be adjustable by rebuilding the server with different configuration options, or by changing options supplied to initdb. postmaster These settings can only be applied when the server starts, so any change requires restarting the server. Values for these settings are typically stored in the postgresql.conf file, or passed on the command line when starting the server. Of course, settings with any of the lower context types can also be set at server start time. sighup Changes to these settings can be made in postgresql.conf without restarting the server. Send a SIGHUP signal to the postmaster to cause it to re-read postgresql.conf and apply the changes. The postmaster will also forward the SIGHUP signal to its child processes so that they all pick up the new value. superuser-backend Changes to these settings can be made in postgresql.conf without restarting the server. They can also be set for a particular session in the connection request packet (for example, via libpq's PGOPTIONS environment variable), but only if the connecting user is a superuser. However, these settings never change in a session after it is started. If you change them in postgresql.conf, send a SIGHUP signal to the postmaster to cause it to re-read postgresql.conf. The new values will only affect subsequently-launched sessions. backend Changes to these settings can be made in postgresql.conf without restarting the server. They can also be set for a particular session in the connection request packet (for example, via libpq's PGOPTIONS environment variable); any user can make such a change for his session. However, these settings never change in a session after it is started. If you change them in postgresql.conf, send a SIGHUP signal to the postmaster to cause it to re-read postgresql.conf. The new values will only affect subsequently-launched sessions. superuser These settings can be set from postgresql.conf, or within a session via the SET command; but only superusers can change them via SET. Changes in postgresql.conf will affect existing sessions only if no session-local value has been established with SET. user These settings can be set from postgresql.conf, or within a session via the SET command. Any user is allowed to change his session-local value. Changes in postgresql.conf will affect existing sessions only if no session-local value has been established with SET. See for more information about the various ways to change these parameters. The pg_settings view cannot be inserted into or deleted from, but it can be updated. An UPDATE applied to a row of pg_settings is equivalent to executing the command on that named parameter. The change only affects the value used by the current session. If an UPDATE is issued within a transaction that is later aborted, the effects of the UPDATE command disappear when the transaction is rolled back. Once the surrounding transaction is committed, the effects will persist until the end of the session, unless overridden by another UPDATE or SET. pg_file_settings The view pg_file_settings provides the file name, line number and value of all parameters which are set through configuration files. In contrast to pg_settings, a row is provided for each occurrence of the parameter across all configuration files. This is helpful for discovering why one value may have been used in preference to another when the parameters were loaded. Name Type Description sourcefile text Path to and name of the configration file sourceline integer Line number within the configuration file where the value was set seqno integer Order in which the setting was loaded name text Run-time configuration parameter name setting text value of the parameter See for more information about the various ways to change these parameters. The pg_file_settings view cannot be modified directly as it represents information, as read in at server start or reload time, about all parameter settings across all configuration files. pg_shadow The view pg_shadow exists for backwards compatibility: it emulates a catalog that existed in PostgreSQL before version 8.1. It shows properties of all roles that are marked as rolcanlogin in pg_authid. The name stems from the fact that this table should not be readable by the public since it contains passwords. pg_user is a publicly readable view on pg_shadow that blanks out the password field. Name Type References Description usename name pg_authid.rolname User name usesysid oid pg_authid.oid ID of this user usecreatedb bool User can create databases usesuper bool User is a superuser userepl bool User can initiate streaming replication and put the system in and out of backup mode. usebypassrls bool User can bypass row level security policies, see for more information. passwd text Password (possibly encrypted); null if none. See pg_authid for details of how encrypted passwords are stored. valuntil abstime Password expiry time (only used for password authentication) useconfig text[] Session defaults for run-time configuration variables pg_stats The view pg_stats provides access to the information stored in the pg_statistic catalog. This view allows access only to rows of pg_statistic that correspond to tables the user has permission to read, and therefore it is safe to allow public read access to this view. pg_stats is also designed to present the information in a more readable format than the underlying catalog — at the cost that its schema must be extended whenever new slot types are defined for pg_statistic. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing table tablename name pg_class.relname Name of table attname name pg_attribute.attname Name of the column described by this row inherited bool If true, this row includes inheritance child columns, not just the values in the specified table null_frac real Fraction of column entries that are null avg_width integer Average width in bytes of column's entries n_distinct real If greater than zero, the estimated number of distinct values in the column. If less than zero, the negative of the number of distinct values divided by the number of rows. (The negated form is used when ANALYZE believes that the number of distinct values is likely to increase as the table grows; the positive form is used when the column seems to have a fixed number of possible values.) For example, -1 indicates a unique column in which the number of distinct values is the same as the number of rows. most_common_vals anyarray A list of the most common values in the column. (Null if no values seem to be more common than any others.) most_common_freqs real[] A list of the frequencies of the most common values, i.e., number of occurrences of each divided by total number of rows. (Null when most_common_vals is.) histogram_bounds anyarray A list of values that divide the column's values into groups of approximately equal population. The values in most_common_vals, if present, are omitted from this histogram calculation. (This column is null if the column data type does not have a < operator or if the most_common_vals list accounts for the entire population.) correlation real Statistical correlation between physical row ordering and logical ordering of the column values. This ranges from -1 to +1. When the value is near -1 or +1, an index scan on the column will be estimated to be cheaper than when it is near zero, due to reduction of random access to the disk. (This column is null if the column data type does not have a < operator.) most_common_elems anyarray A list of non-null element values most often appearing within values of the column. (Null for scalar types.) most_common_elem_freqs real[] A list of the frequencies of the most common element values, i.e., the fraction of rows containing at least one instance of the given value. Two or three additional values follow the per-element frequencies; these are the minimum and maximum of the preceding per-element frequencies, and optionally the frequency of null elements. (Null when most_common_elems is.) elem_count_histogram real[] A histogram of the counts of distinct non-null element values within the values of the column, followed by the average number of distinct non-null elements. (Null for scalar types.) The maximum number of entries in the array fields can be controlled on a column-by-column basis using the ALTER TABLE SET STATISTICS command, or globally by setting the run-time parameter. pg_tables The view pg_tables provides access to useful information about each table in the database. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing table tablename name pg_class.relname Name of table tableowner name pg_authid.rolname Name of table's owner tablespace name pg_tablespace.spcname Name of tablespace containing table (null if default for database) hasindexes boolean pg_class.relhasindex True if table has (or recently had) any indexes hasrules boolean pg_class.relhasrules True if table has (or once had) rules hastriggers boolean pg_class.relhastriggers True if table has (or once had) triggers rowsecurity boolean pg_class.relrowsecurity True if row security is enabled on the table pg_timezone_abbrevs The view pg_timezone_abbrevs provides a list of time zone abbreviations that are currently recognized by the datetime input routines. The contents of this view change when the run-time parameter is modified. Name Type Description abbrev text Time zone abbreviation utc_offset interval Offset from UTC (positive means east of Greenwich) is_dst boolean True if this is a daylight-savings abbreviation pg_timezone_names The view pg_timezone_names provides a list of time zone names that are recognized by SET TIMEZONE, along with their associated abbreviations, UTC offsets, and daylight-savings status. (Technically, PostgreSQL uses UT1 rather than UTC because leap seconds are not handled.) Unlike the abbreviations shown in pg_timezone_abbrevs, many of these names imply a set of daylight-savings transition date rules. Therefore, the associated information changes across local DST boundaries. The displayed information is computed based on the current value of CURRENT_TIMESTAMP. Name Type Description name text Time zone name abbrev text Time zone abbreviation utc_offset interval Offset from UTC (positive means east of Greenwich) is_dst boolean True if currently observing daylight savings pg_user The view pg_user provides access to information about database users. This is simply a publicly readable view of pg_shadow that blanks out the password field. Name Type Description usename name User name usesysid oid ID of this user usecreatedb bool User can create databases usesuper bool User is a superuser userepl bool User can initiate streaming replication and put the system in and out of backup mode. usebypassrls bool User can bypass row level security policies, see for more information. passwd text Not the password (always reads as ********) valuntil abstime Password expiry time (only used for password authentication) useconfig text[] Session defaults for run-time configuration variables pg_user_mappings The view pg_user_mappings provides access to information about user mappings. This is essentially a publicly readable view of pg_user_mapping that leaves out the options field if the user has no rights to use it. Name Type References Description umid oid pg_user_mapping.oid OID of the user mapping srvid oid pg_foreign_server.oid The OID of the foreign server that contains this mapping srvname name pg_foreign_server.srvname Name of the foreign server umuser oid pg_authid.oid OID of the local role being mapped, 0 if the user mapping is public usename name Name of the local user to be mapped umoptions text[] User mapping specific options, as keyword=value strings, if the current user is the owner of the foreign server, else null pg_views The view pg_views provides access to useful information about each view in the database. Name Type References Description schemaname name pg_namespace.nspname Name of schema containing view viewname name pg_class.relname Name of view viewowner name pg_authid.rolname Name of view's owner definition text View definition (a reconstructed SELECT query)