set @save_tmp_table_size=@@tmp_table_size;
set @save_max_heap_table_size=@@max_heap_table_size;
set default_storage_engine=MYISAM;
CREATE TABLE t1 (id INTEGER);
CREATE TABLE t2 (id INTEGER);
INSERT INTO t1 SELECT b.seq FROM seq_1_to_128,seq_1_to_1024 b;
SELECT AVG(DISTINCT id) FROM t1 GROUP BY id % 13;
AVG(DISTINCT id)
513.5000
508.0000
509.0000
510.0000
511.0000
512.0000
513.0000
514.0000
515.0000
516.0000
517.0000
511.5000
512.5000
SELECT SUM(DISTINCT id)/COUNT(DISTINCT id) FROM t1 GROUP BY id % 13;
SUM(DISTINCT id)/COUNT(DISTINCT id)
513.5000
508.0000
509.0000
510.0000
511.0000
512.0000
513.0000
514.0000
515.0000
516.0000
517.0000
511.5000
512.5000
INSERT INTO t1 SELECT b.seq FROM seq_1_to_128,seq_1025_to_16384 b;
INSERT INTO t2 SELECT b.seq FROM seq_1_to_128 a,seq_1_to_16384 b
ORDER by (a.seq*0+b.seq)*rand();
SELECT SUM(DISTINCT id) sm FROM t1;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t2;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t1 group by id % 13;
sm
10327590
10328851
10330112
10331373
10332634
10317510
10318770
10320030
10321290
10322550
10323810
10325070
10326330
SET max_heap_table_size=16384;
SHOW variables LIKE 'max_heap_table_size';
Variable_name	Value
max_heap_table_size	16384
SELECT SUM(DISTINCT id) sm FROM t1;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t2;
sm
134225920
SELECT SUM(DISTINCT id) sm FROM t1 GROUP BY id % 13;
sm
10327590
10328851
10330112
10331373
10332634
10317510
10318770
10320030
10321290
10322550
10323810
10325070
10326330
# 
# Bug mdev-4063: SUM(DISTINCT...) with small'max_heap_table_size 
# (bug #56927)
# 
SET max_heap_table_size=default;
INSERT INTO t1 SELECT b.seq FROM seq_1_to_128,seq_16385_to_32768 b;
TRUNCATE t2;
INSERT INTO t2 SELECT b.seq FROM seq_1_to_128 a,seq_1_to_32768 b
ORDER BY (a.seq*0+b.seq)*rand();
SELECT SUM(DISTINCT id) sm FROM t2;
sm
536887296
SET max_heap_table_size=16384;
SELECT SUM(DISTINCT id) sm FROM t2;
sm
536887296
DROP TABLE t1;
DROP TABLE t2;
SET @@tmp_table_size=@save_tmp_table_size;
SET @@max_heap_table_size=@save_max_heap_table_size;
#
# MDEV-4311: COUNT(DISTINCT...) requiring a file for UNIQUE (bug #68749)
#
CREATE TABLE t2 (id INTEGER) ENGINE=InnoDB;
BEGIN;
INSERT INTO t2 SELECT b.seq FROM seq_1_to_128 a, seq_1_to_16384 b
ORDER BY b.seq*rand();
INSERT INTO t2 VALUE(NULL);
# With default tmp_table_size / max_heap_table_size
SELECT SQL_NO_CACHE count(DISTINCT id) sm FROM t2;
sm
16384
set @@tmp_table_size=1024*256;
# With reduced tmp_table_size
SELECT SQL_NO_CACHE count(DISTINCT id) sm FROM t2;
sm
16384
set @@tmp_table_size=@save_tmp_table_size;
SET @@max_heap_table_size=1024*256;
# With reduced max_heap_table_size
SELECT SQL_NO_CACHE count(DISTINCT id) sm FROM t2;
sm
16384
SET @@max_heap_table_size=@save_max_heap_table_size;
# Back to default tmp_table_size / max_heap_table_size
SELECT SQL_NO_CACHE count(DISTINCT id) sm FROM t2;
sm
16384
COMMIT;
DROP TABLE t2;