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MDEV-25441 WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BY
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.
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@ -1334,3 +1334,37 @@ a b sum(a)
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1 2 1
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1 3 1
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drop table t1;
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#
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# MDEV-25441
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# WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BY
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#
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CREATE TABLE t1 (a INT);
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INSERT INTO t1 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
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explain SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 10 Using temporary
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SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES;
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f
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SELECT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES;
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f
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drop table t1;
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@ -1028,6 +1028,17 @@ group by a, b
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order by (select 1), a
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fetch first 1 rows with ties;
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drop table t1;
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--echo #
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--echo # MDEV-25441
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--echo # WITH TIES is not respected with SQL_BUFFER_RESULT and constant in ORDER BY
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--echo #
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CREATE TABLE t1 (a INT);
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INSERT INTO t1 values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
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explain SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES;
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SELECT SQL_BUFFER_RESULT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES;
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SELECT 1 AS f FROM t1 ORDER BY f FETCH NEXT 2 ROW WITH TIES;
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drop table t1;
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@ -3856,10 +3856,16 @@ JOIN::create_postjoin_aggr_table(JOIN_TAB *tab, List<Item> *table_fields,
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when there is ORDER BY or GROUP BY or there is no GROUP BY, but
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there are aggregate functions, because in all these cases we need
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all result rows.
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We also can not push limit if the limit is WITH TIES, as we do not know
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how many rows we will actually have. This can happen if ORDER BY was
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a constant and removed (during remove_const), thus we have an "unlimited"
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WITH TIES.
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*/
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ha_rows table_rows_limit= ((order == NULL || skip_sort_order) &&
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!table_group &&
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!select_lex->with_sum_func) ? select_limit
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!select_lex->with_sum_func &&
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!unit->lim.is_with_ties()) ? select_limit
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: HA_POS_ERROR;
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if (!(tab->tmp_table_param= new TMP_TABLE_PARAM(tmp_table_param)))
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