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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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15
sql/sql_parse.cc
View File

@ -992,9 +992,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
/*
Multiple queries exits, execute them individually
*/
if (thd->lock || thd->open_tables || thd->derived_tables ||
thd->prelocked_mode)
close_thread_tables(thd);
close_thread_tables(thd);
ulong length= (ulong)(packet_end - next_packet);
log_slow_statement(thd);
@ -1331,12 +1329,11 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
my_message(ER_UNKNOWN_COM_ERROR, ER(ER_UNKNOWN_COM_ERROR), MYF(0));
break;
}
if (thd->lock || thd->open_tables || thd->derived_tables ||
thd->prelocked_mode)
{
thd->proc_info="closing tables";
close_thread_tables(thd); /* Free tables */
}
thd->proc_info= "closing tables";
/* Free tables */
close_thread_tables(thd);
/*
assume handlers auto-commit (if some doesn't - transaction handling
in MySQL should be redesigned to support it; it's a big change,