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import sqlalchemy.sql as sql
import sqlalchemy.exceptions as exceptions
from sqlalchemy import select, MetaData, Table, Column, String, Integer
from sqlalchemy.schema import PassiveDefault, ForeignKeyConstraint
ischema = MetaData()
schemata = Table("schemata", ischema,
Column("catalog_name", String),
Column("schema_name", String),
Column("schema_owner", String),
schema="information_schema")
tables = Table("tables", ischema,
Column("table_catalog", String),
Column("table_schema", String),
Column("table_name", String),
Column("table_type", String),
schema="information_schema")
columns = Table("columns", ischema,
Column("table_schema", String),
Column("table_name", String),
Column("column_name", String),
Column("is_nullable", Integer),
Column("data_type", String),
Column("ordinal_position", Integer),
Column("character_maximum_length", Integer),
Column("numeric_precision", Integer),
Column("numeric_scale", Integer),
Column("column_default", Integer),
schema="information_schema")
constraints = Table("table_constraints", ischema,
Column("table_schema", String),
Column("table_name", String),
Column("constraint_name", String),
Column("constraint_type", String),
schema="information_schema")
column_constraints = Table("constraint_column_usage", ischema,
Column("table_schema", String),
Column("table_name", String),
Column("column_name", String),
Column("constraint_name", String),
schema="information_schema")
pg_key_constraints = Table("key_column_usage", ischema,
Column("table_schema", String),
Column("table_name", String),
Column("column_name", String),
Column("constraint_name", String),
Column("ordinal_position", Integer),
schema="information_schema")
#mysql_key_constraints = Table("key_column_usage", ischema,
# Column("table_schema", String),
# Column("table_name", String),
# Column("column_name", String),
# Column("constraint_name", String),
# Column("referenced_table_schema", String),
# Column("referenced_table_name", String),
# Column("referenced_column_name", String),
# schema="information_schema")
key_constraints = pg_key_constraints
ref_constraints = Table("referential_constraints", ischema,
Column("constraint_catalog", String),
Column("constraint_schema", String),
Column("constraint_name", String),
Column("unique_constraint_catlog", String),
Column("unique_constraint_schema", String),
Column("unique_constraint_name", String),
Column("match_option", String),
Column("update_rule", String),
Column("delete_rule", String),
schema="information_schema")
class ISchema(object):
def __init__(self, engine):
self.engine = engine
self.cache = {}
def __getattr__(self, name):
if name not in self.cache:
# This is a bit of a hack.
# It would probably be better to have a dict
# with just the information_schema tables at
# the module level, so as to avoid returning
# unrelated objects that happen to be named
# 'gen_*'
try:
gen_tbl = globals()['gen_'+name]
except KeyError:
raise exceptions.ArgumentError('information_schema table %s not found' % name)
self.cache[name] = gen_tbl.toengine(self.engine)
return self.cache[name]
def table_names(connection, schema):
s = select([tables.c.table_name], tables.c.table_schema==schema)
return [row[0] for row in connection.execute(s)]
def reflecttable(connection, table, include_columns, ischema_names):
key_constraints = pg_key_constraints
if table.schema is not None:
current_schema = table.schema
else:
current_schema = connection.default_schema_name()
s = select([columns],
sql.and_(columns.c.table_name==table.name,
columns.c.table_schema==current_schema),
order_by=[columns.c.ordinal_position])
c = connection.execute(s)
found_table = False
while True:
row = c.fetchone()
if row is None:
break
#print "row! " + repr(row)
# continue
found_table = True
(name, type, nullable, charlen, numericprec, numericscale, default) = (
row[columns.c.column_name],
row[columns.c.data_type],
row[columns.c.is_nullable] == 'YES',
row[columns.c.character_maximum_length],
row[columns.c.numeric_precision],
row[columns.c.numeric_scale],
row[columns.c.column_default]
)
if include_columns and name not in include_columns:
continue
args = []
for a in (charlen, numericprec, numericscale):
if a is not None:
args.append(a)
coltype = ischema_names[type]
#print "coltype " + repr(coltype) + " args " + repr(args)
coltype = coltype(*args)
colargs= []
if default is not None:
colargs.append(PassiveDefault(sql.text(default)))
table.append_column(Column(name, coltype, nullable=nullable, *colargs))
if not found_table:
raise exceptions.NoSuchTableError(table.name)
# we are relying on the natural ordering of the constraint_column_usage table to return the referenced columns
# in an order that corresponds to the ordinal_position in the key_constraints table, otherwise composite foreign keys
# wont reflect properly. dont see a way around this based on whats available from information_schema
s = select([constraints.c.constraint_name, constraints.c.constraint_type, constraints.c.table_name, key_constraints], use_labels=True, from_obj=[constraints.join(column_constraints, column_constraints.c.constraint_name==constraints.c.constraint_name).join(key_constraints, key_constraints.c.constraint_name==column_constraints.c.constraint_name)], order_by=[key_constraints.c.ordinal_position])
s.append_column(column_constraints)
s.append_whereclause(constraints.c.table_name==table.name)
s.append_whereclause(constraints.c.table_schema==current_schema)
colmap = [constraints.c.constraint_type, key_constraints.c.column_name, column_constraints.c.table_schema, column_constraints.c.table_name, column_constraints.c.column_name, constraints.c.constraint_name, key_constraints.c.ordinal_position]
c = connection.execute(s)
fks = {}
while True:
row = c.fetchone()
if row is None:
break
(type, constrained_column, referred_schema, referred_table, referred_column, constraint_name, ordinal_position) = (
row[colmap[0]],
row[colmap[1]],
row[colmap[2]],
row[colmap[3]],
row[colmap[4]],
row[colmap[5]],
row[colmap[6]]
)
#print "type %s on column %s to remote %s.%s.%s" % (type, constrained_column, referred_schema, referred_table, referred_column)
if type=='PRIMARY KEY':
table.primary_key.add(table.c[constrained_column])
elif type=='FOREIGN KEY':
try:
fk = fks[constraint_name]
except KeyError:
fk = ([],[])
fks[constraint_name] = fk
if current_schema == referred_schema:
referred_schema = table.schema
if referred_schema is not None:
Table(referred_table, table.metadata, autoload=True, schema=referred_schema, autoload_with=connection)
refspec = ".".join([referred_schema, referred_table, referred_column])
else:
Table(referred_table, table.metadata, autoload=True, autoload_with=connection)
refspec = ".".join([referred_table, referred_column])
if constrained_column not in fk[0]:
fk[0].append(constrained_column)
if refspec not in fk[1]:
fk[1].append(refspec)
for name, value in fks.iteritems():
table.append_constraint(ForeignKeyConstraint(value[0], value[1], name=name))
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