Bug#26887 - main.count_distinct3 fails randomly

Streamlined how we increase the size of our test table.
The new method shows run time decreased by ~60%.
This is not a guarantee that we will not see test timeouts (the random failures noted in the bug),
but it should significantly reduce the chances of this occurring.

mysql-test/r/count_distinct3.result

@@ -2,7 +2,8 @@ DROP TABLE IF EXISTS t1, t2;
 CREATE TABLE t1 (id INTEGER, grp TINYINT, id_rev INTEGER);
 SELECT COUNT(*) FROM t1;
 COUNT(*)
-4181000
+4201000
 SELECT COUNT(DISTINCT id) FROM t1 GROUP BY grp;
+# Begin cleanup
+SET session myisam_sort_buffer_size = @orig_myisam_sort_buffer_size;
 DROP TABLE t1;
-set @@read_buffer_size=default;

mysql-test/t/count_distinct3.test

-#
+# Bug #958 a big table without indices and select with group by doesnt work
 # this is a test for error 1032 in count(distinct) + group by, introduced in 
 # mysql-4.1
 #
@@ -21,27 +21,16 @@ while ($1)
   INSERT INTO t1 (id, grp, id_rev) VALUES (@id, @grp, @id_rev); 
   dec $1;
 }
-set @@read_buffer_size=2*1024*1024;
-CREATE TABLE t2 SELECT * FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-INSERT INTO t1 (id, grp, id_rev) SELECT id, grp, id_rev FROM t2;
-INSERT INTO t2 (id, grp, id_rev) SELECT id, grp, id_rev FROM t1;
-DROP TABLE t2;
+
+# We increase the size of t1 here.
+SET @orig_myisam_sort_buffer_size = @@session.myisam_sort_buffer_size;
+SET session myisam_sort_buffer_size=20000000;
+INSERT INTO t1
+SELECT A.id, A.grp, A.id_rev
+FROM 
+  t1 A,
+  (SELECT * FROM t1 B LIMIT 100) B,
+  (SELECT * FROM t1 Z LIMIT 42) Z;
 --enable_query_log
 
 SELECT COUNT(*) FROM t1;
@@ -49,12 +38,12 @@ SELECT COUNT(*) FROM t1;
 # As t1 contains random numbers, results are different from test to test. 
 # That's okay, because we test only that select doesn't yield an
 # error. Note, that --disable_result_log doesn't suppress error output.
-
 --disable_result_log
 SELECT COUNT(DISTINCT id) FROM t1 GROUP BY grp;
 --enable_result_log
-DROP TABLE t1;
 
-set @@read_buffer_size=default;
+--echo # Begin cleanup
+SET session myisam_sort_buffer_size = @orig_myisam_sort_buffer_size;
+DROP TABLE t1;
 
 # End of 4.1 tests