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Bug #45989 take 2 : memory leak after explain encounters an

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error in the query.

Fixes a leak after materializing a GROUP BY subquery to a 
temp table when the subquery has a blob column in the SELECT
list.
Fixed by correctly destructing temporary buffers for re-usable
queries
This commit is contained in:
Georgi Kodinov
2010-02-02 18:30:23 +02:00
parent e3c1c83a16
commit 0569a827ea
4 changed files with 60 additions and 1 deletions
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20
sql/sql_select.h
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@ -354,7 +354,25 @@ public:
*/
bool no_const_tables;
JOIN *tmp_join; ///< copy of this JOIN to be used with temporary tables
/**
Copy of this JOIN to be used with temporary tables.
tmp_join is used when the JOIN needs to be "reusable" (e.g. in a subquery
that gets re-executed several times) and we know will use temporary tables
for materialization. The materialization to a temporary table overwrites the
JOIN structure to point to the temporary table after the materialization is
done. This is where tmp_join is used : it's a copy of the JOIN before the
materialization and is used in restoring before re-execution by overwriting
the current JOIN structure with the saved copy.
Because of this we should pay extra care of not freeing up helper structures
that are referenced by the original contents of the JOIN. We can check for
this by making sure the "current" join is not the temporary copy, e.g.
!tmp_join || tmp_join != join
We should free these sub-structures at JOIN::destroy() if the "current" join
has a copy is not that copy.
*/
JOIN *tmp_join;
ROLLUP rollup; ///< Used with rollup
bool select_distinct; ///< Set if SELECT DISTINCT