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Bug#30882 Dropping a temporary table inside a stored function may cause a server crash

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If a stored function that contains a drop temporary table statement
is invoked by a create temporary table of the same name may cause
a server crash. The problem is that when dropping a table no check
is done to ensure that table is not being used by some outer query
(or outer statement), potentially leaving the outer query with a
reference to a stale (freed) table.

The solution is when dropping a temporary table, always check if
the table is being used by some outer statement as a temporary
table can be dropped inside stored procedures.

The check is performed by looking at the TABLE::query_id value for
temporary tables. To simplify this check and to solve a bug related
to handling of temporary tables in prelocked mode, this patch changes
the way in which this member is used to track the fact that table is
used/unused. Now we ensure that TABLE::query_id is zero for unused
temporary tables (which means that all temporary tables which were
used by a statement should be marked as free for reuse after it's
execution has been completed).
This commit is contained in:
davi@endora.local
2007-11-01 18:52:56 -02:00
parent 6bd9f5c1cb
commit cc007acb78
15 changed files with 431 additions and 83 deletions
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14
sql/sql_handler.cc
View File

@ -151,6 +151,14 @@ static void mysql_ha_close_table(THD *thd, TABLE_LIST *tables)
}
VOID(pthread_mutex_unlock(&LOCK_open));
}
else if (tables->table)
{
/* Must be a temporary table */
TABLE *table= tables->table;
table->file->ha_index_or_rnd_end();
table->query_id= thd->query_id;
table->open_by_handler= 0;
}
}
/*
@ -282,6 +290,12 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
goto err;
}
/*
If it's a temp table, don't reset table->query_id as the table is
being used by this handler. Otherwise, no meaning at all.
*/
tables->table->open_by_handler= 1;
if (! reopen)
send_ok(thd);
DBUG_PRINT("exit",("OK"));