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| author | Vicențiu Ciorbaru <vicentiu@mariadb.org> | 2021-04-18 22:58:34 +0300 |
|---|---|---|
| committer | Vicențiu Ciorbaru <vicentiu@mariadb.org> | 2021-04-21 12:36:57 +0300 |
| commit | 10dd7dec61e22f31bc6f6f3761311fa64be87322 (patch) | |
| tree | 564f95b91f3d520234b16cf504f46610378babd1 | |
| parent | a2db12d8c94d89ff701e4d996e717539ff2e56fd (diff) | |
| download | mariadb-git-bb-10.6-refactor-limit-review.tar.gz | |
MDEV-25441 WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BYbb-10.6-refactor-limit-review
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.
| -rw-r--r-- | mysql-test/main/fetch_first.result | 34 | ||||
| -rw-r--r-- | mysql-test/main/fetch_first.test | 11 | ||||
| -rw-r--r-- | sql/sql_select.cc | 8 |
3 files changed, 52 insertions, 1 deletions
diff --git a/mysql-test/main/fetch_first.result b/mysql-test/main/fetch_first.result index 1e63581e0a5..7bb89633081 100644 --- a/mysql-test/main/fetch_first.result +++ b/mysql-test/main/fetch_first.result @@ -1334,3 +1334,37 @@ a b sum(a) 1 2 1 1 3 1 drop table t1; +# +# MDEV-25441 +# WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BY +# +CREATE TABLE t1 (a INT); +INSERT INTO t1 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10); +explain SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES; +id select_type table type possible_keys key key_len ref rows Extra +1 SIMPLE t1 ALL NULL NULL NULL NULL 10 Using temporary +SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES; +f +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +SELECT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES; +f +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +drop table t1; diff --git a/mysql-test/main/fetch_first.test b/mysql-test/main/fetch_first.test index 6995c1cb5b1..76c0a8b8b39 100644 --- a/mysql-test/main/fetch_first.test +++ b/mysql-test/main/fetch_first.test @@ -1028,6 +1028,17 @@ group by a, b order by (select 1), a fetch first 1 rows with ties; +drop table t1; + +--echo # +--echo # MDEV-25441 +--echo # WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BY +--echo # +CREATE TABLE t1 (a INT); +INSERT INTO t1 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10); +explain SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES; +SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES; +SELECT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES; drop table t1; diff --git a/sql/sql_select.cc b/sql/sql_select.cc index d3c86019e70..32bda234137 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -3816,10 +3816,16 @@ 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))) |