Bug #46159: simple query that never returns

 
The external 'for' loop in remove_dup_with_compare() handled 
HA_ERR_RECORD_DELETED by just starting over without advancing 
to the next record which caused an infinite loop. 
 
This condition could be triggered on certain data by a SELECT 
query containing DISTINCT, GROUP BY and HAVING clauses. 

Fixed remove_dup_with_compare() so that we always advance to 
the next record when receiving HA_ERR_RECORD_DELETED from 
rnd_next(). 

mysql-test/r/distinct.result:
  Added a test case for bug #46159.
mysql-test/t/distinct.test:
  Added a test case for bug #46159.
sql/sql_select.cc:
  Fixed remove_dup_with_compare() so that we always advance to 
  the next record when receiving HA_ERR_RECORD_DELETED from 
  rnd_next().

mysql-test/r/distinct.result

@@ -763,4 +763,34 @@ a	b	d	c
 1	2	0	2
 1	2	0	3
 DROP TABLE t1;
+#
+# Bug #46159: simple query that never returns
+#
+SET @old_max_heap_table_size = @@max_heap_table_size;
+SET @@max_heap_table_size = 16384;
+SET @old_sort_buffer_size = @@sort_buffer_size;
+SET @@sort_buffer_size = 32804;
+CREATE TABLE t1(c1 int, c2 VARCHAR(20));
+INSERT INTO t1 VALUES (1, '1'), (1, '1'), (2, '2'), (3, '1'), (3, '1'), (4, '4');
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+SELECT c1, c2, COUNT(*) FROM t1 GROUP BY c1 LIMIT 4;
+c1	c2	COUNT(*)
+1	1	2
+2	2	1
+3	1	2
+4	4	1
+SELECT DISTINCT c2 FROM t1 GROUP BY c1 HAVING COUNT(*) > 1;
+c2
+1
+5
+DROP TABLE t1;
+SET @@sort_buffer_size = @old_sort_buffer_size;
+SET @@max_heap_table_size = @old_max_heap_table_size;
 End of 5.1 tests

mysql-test/t/distinct.test

@@ -573,4 +573,44 @@ SELECT DISTINCT a, b, d, c FROM t1;
 
 DROP TABLE t1;
 
+--echo #
+--echo # Bug #46159: simple query that never returns
+--echo #
+
+# Set max_heap_table_size to the minimum value so that GROUP BY table in the
+# SELECT query below gets converted to MyISAM
+SET @old_max_heap_table_size = @@max_heap_table_size;
+SET @@max_heap_table_size = 16384;
+
+# Set sort_buffer_size to the mininum value so that remove_duplicates() calls
+# remove_dup_with_compare()
+SET @old_sort_buffer_size = @@sort_buffer_size;
+SET @@sort_buffer_size = 32804;
+
+CREATE TABLE t1(c1 int, c2 VARCHAR(20));
+INSERT INTO t1 VALUES (1, '1'), (1, '1'), (2, '2'), (3, '1'), (3, '1'), (4, '4');
+# Now we just need to pad the table with random data so we have enough unique
+# values to force conversion of the GROUP BY table to MyISAM
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+INSERT INTO t1 SELECT 5 + 10000 * RAND(), '5' FROM t1;
+
+# First rows of the GROUP BY table that will be processed by 
+# remove_dup_with_compare()
+SELECT c1, c2, COUNT(*) FROM t1 GROUP BY c1 LIMIT 4;
+
+# The actual test case
+SELECT DISTINCT c2 FROM t1 GROUP BY c1 HAVING COUNT(*) > 1;
+
+# Cleanup
+
+DROP TABLE t1;
+SET @@sort_buffer_size = @old_sort_buffer_size;
+SET @@max_heap_table_size = @old_max_heap_table_size;
+
 --echo End of 5.1 tests

sql/sql_select.cc

@@ -13665,7 +13665,10 @@ static int remove_dup_with_compare(THD *thd, TABLE *table, Field **first_field,
     if (error)
     {
       if (error == HA_ERR_RECORD_DELETED)
-	continue;
+      {
+        error= file->rnd_next(record);
+        continue;
+      }
       if (error == HA_ERR_END_OF_FILE)
 	break;
       goto err;