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d179bb64c2
This bug is actually two bugs in one, one of which is CREATE TRIGGER under LOCK TABLES and the other is CREATE TRIGGER under LOCK TABLES simultaneous to a FLUSH TABLES WITH READ LOCK (global read lock). Both situations could lead to a server crash or deadlock. The first problem arises from the fact that when under LOCK TABLES, if the table is in the set of locked tables, the table is already open and it doesn't need to be reopened (not a placeholder). Also in this case, if the table is not write locked, a exclusive lock can't be acquired because of a possible deadlock with another thread also holding a (read) lock on the table. The second issue arises from the fact that one should never wait for a global read lock if it's holding any locked tables, because the global read lock is waiting for these tables and this leads to a circular wait deadlock. The solution for the first case is to check if the table is write locked and upgraded the write lock to a exclusive lock and fail otherwise for non write locked tables. Grabbin the exclusive lock in this case also means to ensure that the table is opened only by the calling thread. The second issue is partly fixed by not waiting for the global read lock if the thread is holding any locked tables. The second issue is only partly addressed in this patch because it turned out to be much wider and also affects other DDL statements. Reported as Bug#32395
362 lines
10 KiB
C++
362 lines
10 KiB
C++
/* Copyright (C) 2000-2006 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/*
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Atomic rename of table; RENAME TABLE t1 to t2, tmp to t1 [,...]
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*/
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#include "mysql_priv.h"
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#include "sql_trigger.h"
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static TABLE_LIST *rename_tables(THD *thd, TABLE_LIST *table_list,
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bool skip_error);
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static TABLE_LIST *reverse_table_list(TABLE_LIST *table_list);
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/*
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Every second entry in the table_list is the original name and every
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second entry is the new name.
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*/
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bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent)
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{
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bool error= 1;
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TABLE_LIST *ren_table= 0;
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int to_table;
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char *rename_log_table[2]= {NULL, NULL};
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DBUG_ENTER("mysql_rename_tables");
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/*
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Avoid problems with a rename on a table that we have locked or
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if the user is trying to to do this in a transcation context
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*/
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if (thd->locked_tables || thd->active_transaction())
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{
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my_message(ER_LOCK_OR_ACTIVE_TRANSACTION,
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ER(ER_LOCK_OR_ACTIVE_TRANSACTION), MYF(0));
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DBUG_RETURN(1);
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}
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mysql_ha_rm_tables(thd, table_list, FALSE);
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if (wait_if_global_read_lock(thd,0,1))
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DBUG_RETURN(1);
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if (logger.is_log_table_enabled(QUERY_LOG_GENERAL) ||
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logger.is_log_table_enabled(QUERY_LOG_SLOW))
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{
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/*
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Rules for rename of a log table:
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IF 1. Log tables are enabled
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AND 2. Rename operates on the log table and nothing is being
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renamed to the log table.
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DO 3. Throw an error message.
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ELSE 4. Perform rename.
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*/
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for (to_table= 0, ren_table= table_list; ren_table;
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to_table= 1 - to_table, ren_table= ren_table->next_local)
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{
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int log_table_rename= 0;
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if ((log_table_rename=
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check_if_log_table(ren_table->db_length, ren_table->db,
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ren_table->table_name_length,
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ren_table->table_name, 1)))
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{
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/*
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as we use log_table_rename as an array index, we need it to start
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with 0, while QUERY_LOG_SLOW == 1 and QUERY_LOG_GENERAL == 2.
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So, we shift the value to start with 0;
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*/
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log_table_rename--;
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if (rename_log_table[log_table_rename])
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{
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if (to_table)
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rename_log_table[log_table_rename]= NULL;
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else
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{
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/*
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Two renames of "log_table TO" w/o rename "TO log_table" in
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between.
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*/
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my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), ren_table->table_name,
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ren_table->table_name);
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DBUG_RETURN(1);
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}
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}
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else
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{
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if (to_table)
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{
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/*
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Attempt to rename a table TO log_table w/o renaming
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log_table TO some table.
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*/
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my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), ren_table->table_name,
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ren_table->table_name);
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DBUG_RETURN(1);
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}
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else
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{
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/* save the name of the log table to report an error */
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rename_log_table[log_table_rename]= ren_table->table_name;
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}
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}
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}
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}
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if (rename_log_table[0] || rename_log_table[1])
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{
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if (rename_log_table[0])
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my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), rename_log_table[0],
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rename_log_table[0]);
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else
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my_error(ER_CANT_RENAME_LOG_TABLE, MYF(0), rename_log_table[1],
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rename_log_table[1]);
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DBUG_RETURN(1);
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}
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}
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pthread_mutex_lock(&LOCK_open);
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if (lock_table_names_exclusively(thd, table_list))
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{
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pthread_mutex_unlock(&LOCK_open);
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goto err;
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}
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error=0;
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if ((ren_table=rename_tables(thd,table_list,0)))
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{
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/* Rename didn't succeed; rename back the tables in reverse order */
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TABLE_LIST *table;
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/* Reverse the table list */
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table_list= reverse_table_list(table_list);
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/* Find the last renamed table */
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for (table= table_list;
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table->next_local != ren_table ;
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table= table->next_local->next_local) ;
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table= table->next_local->next_local; // Skip error table
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/* Revert to old names */
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rename_tables(thd, table, 1);
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/* Revert the table list (for prepared statements) */
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table_list= reverse_table_list(table_list);
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error= 1;
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}
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/*
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An exclusive lock on table names is satisfactory to ensure
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no other thread accesses this table.
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However, NDB assumes that handler::rename_tables is called under
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LOCK_open. And it indeed is, from ALTER TABLE.
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TODO: remove this limitation.
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We still should unlock LOCK_open as early as possible, to provide
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higher concurrency - query_cache_invalidate can take minutes to
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complete.
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*/
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pthread_mutex_unlock(&LOCK_open);
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/* Lets hope this doesn't fail as the result will be messy */
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if (!silent && !error)
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{
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write_bin_log(thd, TRUE, thd->query, thd->query_length);
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send_ok(thd);
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}
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if (!error)
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query_cache_invalidate3(thd, table_list, 0);
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pthread_mutex_lock(&LOCK_open);
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unlock_table_names(thd, table_list, (TABLE_LIST*) 0);
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pthread_mutex_unlock(&LOCK_open);
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err:
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start_waiting_global_read_lock(thd);
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DBUG_RETURN(error);
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}
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/*
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reverse table list
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SYNOPSIS
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reverse_table_list()
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table_list pointer to table _list
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RETURN
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pointer to new (reversed) list
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*/
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static TABLE_LIST *reverse_table_list(TABLE_LIST *table_list)
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{
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TABLE_LIST *prev= 0;
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while (table_list)
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{
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TABLE_LIST *next= table_list->next_local;
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table_list->next_local= prev;
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prev= table_list;
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table_list= next;
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}
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return (prev);
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}
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/*
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Rename a single table or a view
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SYNPOSIS
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do_rename()
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thd Thread handle
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ren_table A table/view to be renamed
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new_db The database to which the table to be moved to
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new_table_name The new table/view name
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new_table_alias The new table/view alias
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skip_error Whether to skip error
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DESCRIPTION
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Rename a single table or a view.
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RETURN
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false Ok
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true rename failed
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*/
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bool
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do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db, char *new_table_name,
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char *new_table_alias, bool skip_error)
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{
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int rc= 1;
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char name[FN_REFLEN];
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const char *new_alias, *old_alias;
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frm_type_enum frm_type;
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enum legacy_db_type table_type;
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DBUG_ENTER("do_rename");
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if (lower_case_table_names == 2)
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{
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old_alias= ren_table->alias;
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new_alias= new_table_alias;
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}
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else
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{
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old_alias= ren_table->table_name;
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new_alias= new_table_name;
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}
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build_table_filename(name, sizeof(name),
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new_db, new_alias, reg_ext, 0);
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if (!access(name,F_OK))
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{
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my_error(ER_TABLE_EXISTS_ERROR, MYF(0), new_alias);
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DBUG_RETURN(1); // This can't be skipped
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}
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build_table_filename(name, sizeof(name),
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ren_table->db, old_alias, reg_ext, 0);
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frm_type= mysql_frm_type(thd, name, &table_type);
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switch (frm_type)
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{
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case FRMTYPE_TABLE:
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{
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if (!(rc= mysql_rename_table(ha_resolve_by_legacy_type(thd,
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table_type),
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ren_table->db, old_alias,
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new_db, new_alias, 0)))
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{
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if ((rc= Table_triggers_list::change_table_name(thd, ren_table->db,
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old_alias,
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new_db,
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new_alias)))
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{
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/*
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We've succeeded in renaming table's .frm and in updating
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corresponding handler data, but have failed to update table's
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triggers appropriately. So let us revert operations on .frm
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and handler's data and report about failure to rename table.
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*/
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(void) mysql_rename_table(ha_resolve_by_legacy_type(thd,
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table_type),
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new_db, new_alias,
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ren_table->db, old_alias, 0);
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}
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}
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}
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break;
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case FRMTYPE_VIEW:
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/* change of schema is not allowed */
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if (strcmp(ren_table->db, new_db))
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my_error(ER_FORBID_SCHEMA_CHANGE, MYF(0), ren_table->db,
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new_db);
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else
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rc= mysql_rename_view(thd, new_alias, ren_table);
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break;
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default:
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DBUG_ASSERT(0); // should never happen
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case FRMTYPE_ERROR:
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my_error(ER_FILE_NOT_FOUND, MYF(0), name, my_errno);
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break;
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}
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if (rc && !skip_error)
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DBUG_RETURN(1);
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DBUG_RETURN(0);
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}
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/*
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Rename all tables in list; Return pointer to wrong entry if something goes
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wrong. Note that the table_list may be empty!
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*/
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/*
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Rename tables/views in the list
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SYNPOSIS
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rename_tables()
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thd Thread handle
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table_list List of tables to rename
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skip_error Whether to skip errors
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DESCRIPTION
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Take a table/view name from and odd list element and rename it to a
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the name taken from list element+1. Note that the table_list may be
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empty.
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RETURN
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false Ok
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true rename failed
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*/
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static TABLE_LIST *
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rename_tables(THD *thd, TABLE_LIST *table_list, bool skip_error)
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{
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TABLE_LIST *ren_table, *new_table;
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DBUG_ENTER("rename_tables");
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for (ren_table= table_list; ren_table; ren_table= new_table->next_local)
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{
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new_table= ren_table->next_local;
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if (do_rename(thd, ren_table, new_table->db, new_table->table_name,
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new_table->alias, skip_error))
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DBUG_RETURN(ren_table);
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}
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DBUG_RETURN(0);
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}
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