Fix for MDEV-4219 A simple select query returns random data (upstream bug#68473)
In the case of loose scan used as input for order by, end_send() didn't detect correctly that a loose scan was used, and didn't copy the non-aggregated fields from the temp table used for ORDER BY. The fix uses the fact that the quick select used for sorting is attached to JOIN::pre_sort_join_tab instead of JOIN::join_tab.
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@ -3561,3 +3561,45 @@ id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range NULL PRIMARY 5 NULL 9 Using index for group-by (scanning)
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drop table t1;
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# End of test#50539.
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#
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# MDEV-4219 A simple select query returns random data (upstream bug#68473)
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#
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drop table if exists faulty;
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CREATE TABLE faulty (
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a int(11) unsigned NOT NULL AUTO_INCREMENT,
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b int(11) unsigned NOT NULL,
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c datetime NOT NULL,
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PRIMARY KEY (a),
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UNIQUE KEY b_and_c (b,c)
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);
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INSERT INTO faulty (b, c) VALUES
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(1801, '2013-02-15 09:00:00'),
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(1802, '2013-02-28 09:00:00'),
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(1802, '2013-03-01 09:00:00'),
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(5, '1990-02-15 09:00:00'),
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(5, '2013-02-15 09:00:00'),
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(5, '2009-02-15 17:00:00');
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EXPLAIN
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SELECT DISTINCT b, c FROM faulty WHERE b='1802' ORDER BY c;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE faulty range b_and_c b_and_c 12 NULL 2 Using where; Using index for group-by; Using filesort
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SELECT DISTINCT b, c FROM faulty WHERE b='1802' ORDER BY c;
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b c
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1802 2013-02-28 09:00:00
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1802 2013-03-01 09:00:00
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drop table faulty;
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CREATE TABLE t1 (a INT, b INT);
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INSERT INTO t1 (a, b) VALUES (1,1), (1,2), (1,3);
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INSERT INTO t1 SELECT a + 1, b FROM t1;
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INSERT INTO t1 SELECT a + 2, b FROM t1;
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CREATE INDEX break_it ON t1 (a, b);
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EXPLAIN
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SELECT distinct a, b FROM t1 where a = '3' ORDER BY b;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range break_it break_it 10 NULL 2 Using where; Using index for group-by; Using filesort
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SELECT distinct a, b FROM t1 where a = '3' ORDER BY b;
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a b
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3 1
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3 2
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3 3
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drop table t1;
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@ -1400,3 +1400,50 @@ explain SELECT f1, COUNT(DISTINCT f2) FROM t1 GROUP BY f1;
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drop table t1;
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--echo # End of test#50539.
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--echo #
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--echo # MDEV-4219 A simple select query returns random data (upstream bug#68473)
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--echo #
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--disable_warnings
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drop table if exists faulty;
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--enable_warnings
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# MySQL's test case
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CREATE TABLE faulty (
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a int(11) unsigned NOT NULL AUTO_INCREMENT,
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b int(11) unsigned NOT NULL,
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c datetime NOT NULL,
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PRIMARY KEY (a),
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UNIQUE KEY b_and_c (b,c)
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);
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INSERT INTO faulty (b, c) VALUES
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(1801, '2013-02-15 09:00:00'),
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(1802, '2013-02-28 09:00:00'),
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(1802, '2013-03-01 09:00:00'),
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(5, '1990-02-15 09:00:00'),
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(5, '2013-02-15 09:00:00'),
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(5, '2009-02-15 17:00:00');
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EXPLAIN
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SELECT DISTINCT b, c FROM faulty WHERE b='1802' ORDER BY c;
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SELECT DISTINCT b, c FROM faulty WHERE b='1802' ORDER BY c;
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drop table faulty;
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# MariaDB test case
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CREATE TABLE t1 (a INT, b INT);
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INSERT INTO t1 (a, b) VALUES (1,1), (1,2), (1,3);
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INSERT INTO t1 SELECT a + 1, b FROM t1;
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INSERT INTO t1 SELECT a + 2, b FROM t1;
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CREATE INDEX break_it ON t1 (a, b);
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EXPLAIN
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SELECT distinct a, b FROM t1 where a = '3' ORDER BY b;
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SELECT distinct a, b FROM t1 where a = '3' ORDER BY b;
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drop table t1;
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@ -13217,7 +13217,11 @@ QUICK_GROUP_MIN_MAX_SELECT::~QUICK_GROUP_MIN_MAX_SELECT()
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DBUG_ASSERT(file == head->file);
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if (doing_key_read)
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head->disable_keyread();
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file->ha_index_end();
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/*
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There may be a code path when the same table was first accessed by index,
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then the index is closed, and the table is scanned (order by + loose scan).
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*/
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file->ha_index_or_rnd_end();
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}
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if (min_max_arg_part)
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delete_dynamic(&min_max_ranges);
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@ -17404,7 +17404,13 @@ end_send(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
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if (!end_of_records)
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{
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if (join->table_count &&
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join->join_tab->is_using_loose_index_scan())
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(join->join_tab->is_using_loose_index_scan() ||
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/*
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When order by used a loose scan as its input, the quick select may
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be attached to pre_sort_join_tab.
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*/
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(join->pre_sort_join_tab &&
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join->pre_sort_join_tab->is_using_loose_index_scan())))
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{
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/* Copy non-aggregated fields when loose index scan is used. */
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copy_fields(&join->tmp_table_param);
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