From 1a48dd4e2bf0c6353bbf76b1f9b768620e0aa090 Mon Sep 17 00:00:00 2001 From: Georgi Kodinov Date: Wed, 7 Oct 2009 18:03:42 +0300 Subject: Bug #43029: FORCE INDEX FOR ORDER BY is ignored when join buffering is used FORCE INDEX FOR ORDER BY now prevents the optimizer from using join buffering. As a result the optimizer can use indexed access on the first table and doesn't need to sort the complete resultset at the end of the statement. --- sql/table.cc | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) (limited to 'sql/table.cc') diff --git a/sql/table.cc b/sql/table.cc index 04f2a3fbcf8..d2538eb4d59 100644 --- a/sql/table.cc +++ b/sql/table.cc @@ -4637,7 +4637,8 @@ Item_subselect *TABLE_LIST::containing_subselect() (TABLE_LIST::index_hints). Using the information in this tagged list this function sets the members st_table::keys_in_use_for_query, st_table::keys_in_use_for_group_by, st_table::keys_in_use_for_order_by, - st_table::force_index and st_table::covering_keys. + st_table::force_index, st_table::force_index_order, + st_table::force_index_group and st_table::covering_keys. Current implementation of the runtime does not allow mixing FORCE INDEX and USE INDEX, so this is checked here. Then the FORCE INDEX list @@ -4765,14 +4766,28 @@ bool TABLE_LIST::process_index_hints(TABLE *tbl) } /* process FORCE INDEX as USE INDEX with a flag */ + if (!index_order[INDEX_HINT_FORCE].is_clear_all()) + { + tbl->force_index_order= TRUE; + index_order[INDEX_HINT_USE].merge(index_order[INDEX_HINT_FORCE]); + } + + if (!index_group[INDEX_HINT_FORCE].is_clear_all()) + { + tbl->force_index_group= TRUE; + index_group[INDEX_HINT_USE].merge(index_group[INDEX_HINT_FORCE]); + } + + /* + TODO: get rid of tbl->force_index (on if any FORCE INDEX is specified) and + create tbl->force_index_join instead. + Then use the correct force_index_XX instead of the global one. + */ if (!index_join[INDEX_HINT_FORCE].is_clear_all() || - !index_order[INDEX_HINT_FORCE].is_clear_all() || - !index_group[INDEX_HINT_FORCE].is_clear_all()) + tbl->force_index_group || tbl->force_index_order) { tbl->force_index= TRUE; index_join[INDEX_HINT_USE].merge(index_join[INDEX_HINT_FORCE]); - index_order[INDEX_HINT_USE].merge(index_order[INDEX_HINT_FORCE]); - index_group[INDEX_HINT_USE].merge(index_group[INDEX_HINT_FORCE]); } /* apply USE INDEX */ -- cgit v1.2.1