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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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62
mysql-test/r/handler_myisam.result
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@ -575,3 +575,65 @@ ERROR 42S02: Table 'test.t1' doesn't exist
handler t1 close;
handler t2 close;
drop table t2;
drop table if exists t1;
create temporary table t1 (a int, b char(1), key a(a), key b(a,b));
insert into t1 values (0,"a"),(1,"b"),(2,"c"),(3,"d"),(4,"e"),
(5,"f"),(6,"g"),(7,"h"),(8,"i"),(9,"j");
select a,b from t1;
a b
0 a
1 b
2 c
3 d
4 e
5 f
6 g
7 h
8 i
9 j
handler t1 open as a1;
handler a1 read a first;
a b
0 a
handler a1 read a next;
a b
1 b
handler a1 read a next;
a b
2 c
select a,b from t1;
ERROR HY000: Can't reopen table: 'a1'
handler a1 read a prev;
a b
1 b
handler a1 read a prev;
a b
0 a
handler a1 read a=(6) where b="g";
a b
6 g
handler a1 close;
select a,b from t1;
a b
0 a
1 b
2 c
3 d
4 e
5 f
6 g
7 h
8 i
9 j
handler t1 open as a2;
handler a2 read a first;
a b
0 a
handler a2 read a last;
a b
9 j
handler a2 read a prev;
a b
8 i
handler a2 close;
drop table t1;