Hi! Everything looks OK, except one small style error. Also it would be nice to put somewhere 'TODO:' to bring in order 'uncachable' flags. On 03.03.2011 14:07, timour@askmonty.org wrote:

At file:///home/tsk/mprog/src/5.3/

------------------------------------------------------------ revno: 2929 revision-id: timour@askmonty.org-20110303120726-la5o40rldim2t93y parent: psergey@askmonty.org-20110301072222-1rmapkelx9l1kw8u committer: timour@askmonty.org branch nick: 5.3 timestamp: Thu 2011-03-03 14:07:26 +0200 message: Fix LP BUG#718763

Analysis: The reason for the crash was that the inner subquery was executed via a scan on a final temporary table applied after all other operations. This final operation is implemented by changing the contents of the JOIN object of the subquery to represent a table scan over the temp table. At the same time query optimization of the outer subquery required evaluation of the inner subquery, which happened before the actual EXPLAIN. The evaluation left the JOIN object of the inner subquery in the changed state, where it represented a table scan over a temp table, and EXPLAIN crashed because the temp table is not associated with any table reference (TABLE_LIST object). The reason the JOIN was not restored was because its saving/restoration was controlled by the join->select_lex->uncacheable flag, which was not set in the case of materialization.

Solution: In the methods Item_in_subselect::[single | row]_value_transformer() set: select_lex->uncacheable|= UNCACHEABLE_EXPLAIN; In addition, for symmetry, change: master_unit->uncacheable|= UNCACHEABLE_EXPLAIN; instead of UNCACHEABLE_DEPENDENT because if a subquery was not dependent initially, the changed methods do not change this fact. The subquery may later become correlated if it is transformed to an EXISTS query, but it may stay uncorrelated if executed via materialization. [skip]

@@ -1742,7 +1752,15 @@ Item_in_subselect::row_value_transformer optimizer->keep_top_level_cache();

thd->lex->current_select= current; - master_unit->uncacheable|= UNCACHEABLE_DEPENDENT; + /* + The uncacheable property controls a number of actions, e.g. whether to + save/restore (via init_save_join_tab/restore_tmp) the original JOIN for + plans with a temp table where the original JOIN was overriden by + make_simple_join. The UNCACHEABLE_EXPLAIN is ignored by EXPLAIN, thus + non-correlated subqueries will not appear as such to EXPLAIN. + */ + master_unit->uncacheable|=UNCACHEABLE_EXPLAIN; + select_lex->uncacheable|= UNCACHEABLE_EXPLAIN;

if (!abort_on_null&& left_expr->maybe_null&& !pushed_cond_guards) {

put space (' ') after '=' [skip]

_______________________________________________ commits mailing list commits@mariadb.org https://lists.askmonty.org/cgi-bin/mailman/listinfo/commits