/* Copyright (c) 2010, 2015, Oracle and/or its affiliates.
Copyright (c) 2013, 2015, MariaDB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#include "debug_sync.h" // DEBUG_SYNC
#include "table.h" // TABLE, FOREIGN_KEY_INFO
#include "sql_class.h" // THD
#include "sql_base.h" // open_and_lock_tables
#include "sql_table.h" // write_bin_log
#include "datadict.h" // dd_recreate_table()
#include "lock.h" // MYSQL_OPEN_* flags
#include "sql_acl.h" // DROP_ACL
#include "sql_parse.h" // check_one_table_access()
#include "sql_truncate.h"
#include "sql_show.h" //append_identifier()
/**
Append a list of field names to a string.
@param str The string.
@param fields The list of field names.
@return TRUE on failure, FALSE otherwise.
*/
static bool fk_info_append_fields(THD *thd, String *str,
List<LEX_STRING> *fields)
{
bool res= FALSE;
LEX_STRING *field;
List_iterator_fast<LEX_STRING> it(*fields);
while ((field= it++))
{
res|= append_identifier(thd, str, field->str, field->length);
res|= str->append(", ");
}
str->chop();
str->chop();
return res;
}
/**
Generate a foreign key description suitable for a error message.
@param thd Thread context.
@param fk_info The foreign key information.
@return A human-readable string describing the foreign key.
*/
static const char *fk_info_str(THD *thd, FOREIGN_KEY_INFO *fk_info)
{
bool res= FALSE;
char buffer[STRING_BUFFER_USUAL_SIZE*2];
String str(buffer, sizeof(buffer), system_charset_info);
str.length(0);
/*
`db`.`tbl`, CONSTRAINT `id` FOREIGN KEY (`fk`) REFERENCES `db`.`tbl` (`fk`)
*/
res|= append_identifier(thd, &str, fk_info->foreign_db->str,
fk_info->foreign_db->length);
res|= str.append(".");
res|= append_identifier(thd, &str, fk_info->foreign_table->str,
fk_info->foreign_table->length);
res|= str.append(", CONSTRAINT ");
res|= append_identifier(thd, &str, fk_info->foreign_id->str,
fk_info->foreign_id->length);
res|= str.append(" FOREIGN KEY (");
res|= fk_info_append_fields(thd, &str, &fk_info->foreign_fields);
res|= str.append(") REFERENCES ");
res|= append_identifier(thd, &str, fk_info->referenced_db->str,
fk_info->referenced_db->length);
res|= str.append(".");
res|= append_identifier(thd, &str, fk_info->referenced_table->str,
fk_info->referenced_table->length);
res|= str.append(" (");
res|= fk_info_append_fields(thd, &str, &fk_info->referenced_fields);
res|= str.append(')');
return res ? NULL : thd->strmake(str.ptr(), str.length());
}
/**
Check and emit a fatal error if the table which is going to be
affected by TRUNCATE TABLE is a parent table in some non-self-
referencing foreign key.
@remark The intention is to allow truncate only for tables that
are not dependent on other tables.
@param thd Thread context.
@param table Table handle.
@retval FALSE This table is not parent in a non-self-referencing foreign
key. Statement can proceed.
@retval TRUE This table is parent in a non-self-referencing foreign key,
error was emitted.
*/
static bool
fk_truncate_illegal_if_parent(THD *thd, TABLE *table)
{
FOREIGN_KEY_INFO *fk_info;
List<FOREIGN_KEY_INFO> fk_list;
List_iterator_fast<FOREIGN_KEY_INFO> it;
/*
Bail out early if the table is not referenced by a foreign key.
In this case, the table could only be, if at all, a child table.
*/
if (! table->file->referenced_by_foreign_key())
return FALSE;
/*
This table _is_ referenced by a foreign key. At this point, only
self-referencing keys are acceptable. For this reason, get the list
of foreign keys referencing this table in order to check the name
of the child (dependent) tables.
*/
table->file->get_parent_foreign_key_list(thd, &fk_list);
/* Out of memory when building list. */
if (thd->is_error())
return TRUE;
it.init(fk_list);
/* Loop over the set of foreign keys for which this table is a parent. */
while ((fk_info= it++))
{
DBUG_ASSERT(!my_strcasecmp(system_charset_info,
fk_info->referenced_db->str,
table->s->db.str));
DBUG_ASSERT(!my_strcasecmp(system_charset_info,
fk_info->referenced_table->str,
table->s->table_name.str));
if (my_strcasecmp(system_charset_info, fk_info->foreign_db->str,
table->s->db.str) ||
my_strcasecmp(system_charset_info, fk_info->foreign_table->str,
table->s->table_name.str))
break;
}
/* Table is parent in a non-self-referencing foreign key. */
if (fk_info)
{
my_error(ER_TRUNCATE_ILLEGAL_FK, MYF(0), fk_info_str(thd, fk_info));
return TRUE;
}
return FALSE;
}
/*
Open and truncate a locked table.
@param thd Thread context.
@param table_ref Table list element for the table to be truncated.
@param is_tmp_table True if element refers to a temp table.
@retval TRUNCATE_OK Truncate was successful and statement can be safely
binlogged.
@retval TRUNCATE_FAILED_BUT_BINLOG Truncate failed but still go ahead with
binlogging as in case of non transactional tables
partial truncation is possible.
@retval TRUNCATE_FAILED_SKIP_BINLOG Truncate was not successful hence donot
binlong the statement.
*/
enum Sql_cmd_truncate_table::truncate_result
Sql_cmd_truncate_table::handler_truncate(THD *thd, TABLE_LIST *table_ref,
bool is_tmp_table)
{
int error= 0;
uint flags= 0;
DBUG_ENTER("Sql_cmd_truncate_table::handler_truncate");
/*
Can't recreate, the engine must mechanically delete all rows
in the table. Use open_and_lock_tables() to open a write cursor.
*/
/* If it is a temporary table, no need to take locks. */
if (!is_tmp_table)
{
/* We don't need to load triggers. */
DBUG_ASSERT(table_ref->trg_event_map == 0);
/*
Our metadata lock guarantees that no transaction is reading
or writing into the table. Yet, to open a write cursor we need
a thr_lock lock. Allow to open base tables only.
*/
table_ref->required_type= FRMTYPE_TABLE;
/*
Ignore pending FLUSH TABLES since we don't want to release
the MDL lock taken above and otherwise there is no way to
wait for FLUSH TABLES in deadlock-free fashion.
*/
flags= MYSQL_OPEN_IGNORE_FLUSH;
/*
Even though we have an MDL lock on the table here, we don't
pass MYSQL_OPEN_HAS_MDL_LOCK to open_and_lock_tables
since to truncate a MERGE table, we must open and lock
merge children, and on those we don't have an MDL lock.
Thus clear the ticket to satisfy MDL asserts.
*/
table_ref->mdl_request.ticket= NULL;
}
/* Open the table as it will handle some required preparations. */
if (open_and_lock_tables(thd, table_ref, FALSE, flags))
DBUG_RETURN(TRUNCATE_FAILED_SKIP_BINLOG);
/* Whether to truncate regardless of foreign keys. */
if (! (thd->variables.option_bits & OPTION_NO_FOREIGN_KEY_CHECKS))
if (fk_truncate_illegal_if_parent(thd, table_ref->table))
DBUG_RETURN(TRUNCATE_FAILED_SKIP_BINLOG);
error= table_ref->table->file->ha_truncate();
if (error)
{
table_ref->table->file->print_error(error, MYF(0));
/*
If truncate method is not implemented then we don't binlog the
statement. If truncation has failed in a transactional engine then also we
donot binlog the statment. Only in non transactional engine we binlog
inspite of errors.
*/
if (error == HA_ERR_WRONG_COMMAND ||
table_ref->table->file->has_transactions())
DBUG_RETURN(TRUNCATE_FAILED_SKIP_BINLOG);
else
DBUG_RETURN(TRUNCATE_FAILED_BUT_BINLOG);
}
DBUG_RETURN(TRUNCATE_OK);
}
/*
Close and recreate a temporary table. In case of success,
write truncate statement into the binary log if in statement
mode.
@param thd Thread context.
@param table The temporary table.
@retval FALSE Success.
@retval TRUE Error.
*/
static bool recreate_temporary_table(THD *thd, TABLE *table)
{
bool error= TRUE;
TABLE_SHARE *share= table->s;
handlerton *table_type= table->s->db_type();
TABLE *new_table;
DBUG_ENTER("recreate_temporary_table");
table->file->info(HA_STATUS_AUTO | HA_STATUS_NO_LOCK);
/*
If LOCK TABLES list is not empty and contains this table
then unlock the table and remove it from this list.
*/
mysql_lock_remove(thd, thd->lock, table);
/* Don't free share. */
close_temporary_table(thd, table, FALSE, FALSE);
dd_recreate_table(thd, share->db.str, share->table_name.str,
share->normalized_path.str);
if ((new_table= open_table_uncached(thd, table_type, share->path.str,
share->db.str,
share->table_name.str, true, true)))
{
error= FALSE;
thd->thread_specific_used= TRUE;
new_table->s->table_creation_was_logged= share->table_creation_was_logged;
}
else
rm_temporary_table(table_type, share->path.str);
free_table_share(share);
my_free(table);
DBUG_RETURN(error);
}
/*
Handle locking a base table for truncate.
@param[in] thd Thread context.
@param[in] table_ref Table list element for the table to
be truncated.
@param[out] hton_can_recreate Set to TRUE if table can be dropped
and recreated.
@retval FALSE Success.
@retval TRUE Error.
*/
bool Sql_cmd_truncate_table::lock_table(THD *thd, TABLE_LIST *table_ref,
bool *hton_can_recreate)
{
TABLE *table= NULL;
DBUG_ENTER("Sql_cmd_truncate_table::lock_table");
/* Lock types are set in the parser. */
DBUG_ASSERT(table_ref->lock_type == TL_WRITE);
/* The handler truncate protocol dictates a exclusive lock. */
DBUG_ASSERT(table_ref->mdl_request.type == MDL_EXCLUSIVE);
/*
Before doing anything else, acquire a metadata lock on the table,
or ensure we have one. We don't use open_and_lock_tables()
right away because we want to be able to truncate (and recreate)
corrupted tables, those that we can't fully open.
MySQL manual documents that TRUNCATE can be used to repair a
damaged table, i.e. a table that can not be fully "opened".
In particular MySQL manual says: As long as the table format
file tbl_name.frm is valid, the table can be re-created as
an empty table with TRUNCATE TABLE, even if the data or index
files have become corrupted.
*/
if (thd->locked_tables_mode)
{
if (!(table= find_table_for_mdl_upgrade(thd, table_ref->db,
table_ref->table_name, FALSE)))
DBUG_RETURN(TRUE);
*hton_can_recreate= ha_check_storage_engine_flag(table->s->db_type(),
HTON_CAN_RECREATE);
table_ref->mdl_request.ticket= table->mdl_ticket;
}
else
{
/* Acquire an exclusive lock. */
DBUG_ASSERT(table_ref->next_global == NULL);
if (lock_table_names(thd, table_ref, NULL,
thd->variables.lock_wait_timeout, 0))
DBUG_RETURN(TRUE);
handlerton *hton;
if (!ha_table_exists(thd, table_ref->db, table_ref->table_name, &hton) ||
hton == view_pseudo_hton)
{
my_error(ER_NO_SUCH_TABLE, MYF(0), table_ref->db, table_ref->table_name);
DBUG_RETURN(TRUE);
}
if (!hton)
{
/*
The table exists, but its storage engine is unknown, perhaps not
loaded at the moment. We need to open and parse the frm to know the
storage engine in question, so let's proceed with the truncation and
try to open the table. This will produce the correct error message
about unknown engine.
*/
*hton_can_recreate= false;
}
else
*hton_can_recreate= hton->flags & HTON_CAN_RECREATE;
}
/*
A storage engine can recreate or truncate the table only if there
are no references to it from anywhere, i.e. no cached TABLE in the
table cache.
*/
if (thd->locked_tables_mode)
{
DEBUG_SYNC(thd, "upgrade_lock_for_truncate");
/* To remove the table from the cache we need an exclusive lock. */
if (wait_while_table_is_used(thd, table, HA_EXTRA_PREPARE_FOR_DROP))
DBUG_RETURN(TRUE);
m_ticket_downgrade= table->mdl_ticket;
/* Close if table is going to be recreated. */
if (*hton_can_recreate)
close_all_tables_for_name(thd, table->s, HA_EXTRA_NOT_USED, NULL);
}
else
{
/* Table is already locked exclusively. Remove cached instances. */
tdc_remove_table(thd, TDC_RT_REMOVE_ALL, table_ref->db,
table_ref->table_name, FALSE);
}
DBUG_RETURN(FALSE);
}
/*
Optimized delete of all rows by doing a full generate of the table.
@remark Will work even if the .MYI and .MYD files are destroyed.
In other words, it works as long as the .FRM is intact and
the engine supports re-create.
@param thd Thread context.
@param table_ref Table list element for the table to be truncated.
@retval FALSE Success.
@retval TRUE Error.
*/
bool Sql_cmd_truncate_table::truncate_table(THD *thd, TABLE_LIST *table_ref)
{
int error;
bool binlog_stmt;
DBUG_ENTER("Sql_cmd_truncate_table::truncate_table");
DBUG_ASSERT((!table_ref->table) ||
(table_ref->table && table_ref->table->s));
/* Initialize, or reinitialize in case of reexecution (SP). */
m_ticket_downgrade= NULL;
/* If it is a temporary table, no need to take locks. */
if (is_temporary_table(table_ref))
{
TABLE *tmp_table= table_ref->table;
/* In RBR, the statement is not binlogged if the table is temporary. */
binlog_stmt= !thd->is_current_stmt_binlog_format_row();
/* Note that a temporary table cannot be partitioned. */
if (ha_check_storage_engine_flag(tmp_table->s->db_type(),
HTON_CAN_RECREATE))
{
if ((error= recreate_temporary_table(thd, tmp_table)))
binlog_stmt= FALSE; /* No need to binlog failed truncate-by-recreate. */
DBUG_ASSERT(! thd->transaction.stmt.modified_non_trans_table);
}
else
{
/*
The engine does not support truncate-by-recreate. Open the
table and invoke the handler truncate. In such a manner this
can in fact open several tables if it's a temporary MyISAMMRG
table.
*/
error= handler_truncate(thd, table_ref, TRUE);
}
/*
No need to invalidate the query cache, queries with temporary
tables are not in the cache. No need to write to the binary
log a failed row-by-row delete even if under RBR as the table
might not exist on the slave.
*/
}
else /* It's not a temporary table. */
{
bool hton_can_recreate;
if (lock_table(thd, table_ref, &hton_can_recreate))
DBUG_RETURN(TRUE);
if (hton_can_recreate)
{
/*
The storage engine can truncate the table by creating an
empty table with the same structure.
*/
error= dd_recreate_table(thd, table_ref->db, table_ref->table_name);
if (thd->locked_tables_mode && thd->locked_tables_list.reopen_tables(thd))
thd->locked_tables_list.unlink_all_closed_tables(thd, NULL, 0);
/* No need to binlog a failed truncate-by-recreate. */
binlog_stmt= !error;
}
else
{
/*
The engine does not support truncate-by-recreate.
Attempt to use the handler truncate method.
*/
error= handler_truncate(thd, table_ref, FALSE);
/*
All effects of a TRUNCATE TABLE operation are committed even if
truncation fails in the case of non transactional tables. Thus, the
query must be written to the binary log. The only exception is a
unimplemented truncate method.
*/
if (error == TRUNCATE_OK || error == TRUNCATE_FAILED_BUT_BINLOG)
binlog_stmt= true;
else
binlog_stmt= false;
}
/*
If we tried to open a MERGE table and failed due to problems with the
children tables, the table will have been closed and table_ref->table
will be invalid. Reset the pointer here in any case as
query_cache_invalidate does not need a valid TABLE object.
*/
table_ref->table= NULL;
query_cache_invalidate3(thd, table_ref, FALSE);
}
/* DDL is logged in statement format, regardless of binlog format. */
if (binlog_stmt)
error|= write_bin_log(thd, !error, thd->query(), thd->query_length());
/*
A locked table ticket was upgraded to a exclusive lock. After the
the query has been written to the binary log, downgrade the lock
to a shared one.
*/
if (m_ticket_downgrade)
m_ticket_downgrade->downgrade_lock(MDL_SHARED_NO_READ_WRITE);
DBUG_RETURN(error);
}
/**
Execute a TRUNCATE statement at runtime.
@param thd The current thread.
@return FALSE on success.
*/
bool Sql_cmd_truncate_table::execute(THD *thd)
{
bool res= TRUE;
TABLE_LIST *first_table= thd->lex->select_lex.table_list.first;
DBUG_ENTER("Sql_cmd_truncate_table::execute");
if (check_one_table_access(thd, DROP_ACL, first_table))
DBUG_RETURN(res);
if (! (res= truncate_table(thd, first_table)))
my_ok(thd);
DBUG_RETURN(res);
}