Hello Igor, I've discovered the following:
Consider a testcase for https://bugs.launchpad.net/maria/+bug/803365. There we have a query that's using a derived table that's on the inner side of an outer join: SELECT * FROM t1 WHERE t1.f1 IN ( SELECT t2.f2 FROM t2 LEFT JOIN ( SELECT * FROM t3 ) AS alias1 ON alias1.f3 = t2.f2 ); If I follow it in debugger to right after simplify_joins(), I can see this structure (the [] brackets denote List<TABLE_LIST> bounds): ['t1'---'(sj-nest)'] | ['alias1'---'t2' ] | [t3] 'alias1' is on the inner side of an outer join (it has non-NULL on_expr, and outer_join==1). It has got a single child, t3, which has on_expr==NULL and outer_join==0. Is it really correct that simplify_joins() didn't remove 'alias1', like it does with regular join nests? Could it be that simplify_joins() code can't handle single-child join nests just because the parser never produced them (but after conversion of derived tables to join nests they are now possible?) BR Sergey -- Sergey Petrunia, Software Developer Monty Program AB, http://askmonty.org Blog: http://s.petrunia.net/blog _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
