Commit 65931211 authored by Igor Babaev's avatar Igor Babaev

Fixed bug mdev-4025.

The bug could lead to a wrong estimate of the number of expected rows
in the output of the EXPLAIN commands for queries with GROUP BY.
This could be observed in the test case for LP bug 934348.
parent f8c8f96e
......@@ -2978,7 +2978,7 @@ EXPLAIN
SELECT a FROM t1 t WHERE a IN (SELECT b FROM t1, t2 WHERE b = a)
GROUP BY a HAVING a != 'z';
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t index idx_a idx_a 4 NULL 1 Using index
1 PRIMARY t index idx_a idx_a 4 NULL 3 Using index
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 2 Using where
2 MATERIALIZED t1 ref idx_a idx_a 4 test.t2.b 2 Using index
......@@ -2992,7 +2992,7 @@ EXPLAIN
SELECT a FROM t1 t WHERE a IN (SELECT b FROM t1, t2 WHERE b = a)
GROUP BY a HAVING a != 'z';
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t index idx_a idx_a 4 NULL 1 Using index
1 PRIMARY t index idx_a idx_a 4 NULL 3 Using index
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 2 Using where
2 MATERIALIZED t1 ref idx_a idx_a 4 test.t2.b 2 Using index
......
......@@ -18371,6 +18371,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit_arg,
and as result we'll choose an index scan when using ref/range
access + filesort will be cheaper.
*/
if (select_limit_arg != HA_POS_ERROR)
select_limit= (ha_rows) (select_limit < fanout ?
1 : select_limit/fanout);
/*
......
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