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MDEV-25441 WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BY

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Pushing LIMIT to temp aggregation table is possible, but not when WITH
TIES is used. In a degenerate case with constant ORDER BY, the constant
gets removed and the code assumed the limit is push-able.

Ensure that if WITH TIES is present, that this does not happen.
This commit is contained in:
Vicențiu Ciorbaru
2021-04-18 22:58:34 +03:00
parent 44a6af65f5
commit aeccdddedd
3 changed files with 52 additions and 1 deletions
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8
sql/sql_select.cc
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@ -3856,10 +3856,16 @@ JOIN::create_postjoin_aggr_table(JOIN_TAB *tab, List<Item> *table_fields,
when there is ORDER BY or GROUP BY or there is no GROUP BY, but
there are aggregate functions, because in all these cases we need
all result rows.
We also can not push limit if the limit is WITH TIES, as we do not know
how many rows we will actually have. This can happen if ORDER BY was
a constant and removed (during remove_const), thus we have an "unlimited"
WITH TIES.
*/
ha_rows table_rows_limit= ((order == NULL || skip_sort_order) &&
!table_group &&
!select_lex->with_sum_func) ? select_limit
!select_lex->with_sum_func &&
!unit->lim.is_with_ties()) ? select_limit
: HA_POS_ERROR;
if (!(tab->tmp_table_param= new TMP_TABLE_PARAM(tmp_table_param)))