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mysql-test/r/group_min_max.result

@@ -2502,3 +2502,61 @@ a	MAX(b)
 2	1
 DROP TABLE t;
 End of 5.0 tests
+CREATE TABLE t1 ( a INT, b INT, c INT, KEY bc(b, c) )
+PARTITION BY KEY (a, b) PARTITIONS 3
+;
+INSERT INTO t1 VALUES
+(17, 1, -8),
+(3,  1, -7),
+(23, 1, -6),
+(22, 1, -5),
+(11, 1, -4),
+(21, 1, -3),
+(19, 1, -2),
+(30, 1, -1),
+(20, 1, 1),
+(16, 1, 2),
+(18, 1, 3),
+(9,  1, 4),
+(15, 1, 5),
+(28, 1, 6),
+(29, 1, 7),
+(25, 1, 8),
+(10, 1, 9),
+(13, 1, 10),
+(27, 1, 11),
+(24, 1, 12),
+(12, 1, 13),
+(26, 1, 14),
+(14, 1, 15)
+;
+SELECT b, c FROM t1 WHERE b = 1 GROUP BY b, c;
+b	c
+1	-8
+1	-7
+1	-6
+1	-5
+1	-4
+1	-3
+1	-2
+1	-1
+1	1
+1	2
+1	3
+1	4
+1	5
+1	6
+1	7
+1	8
+1	9
+1	10
+1	11
+1	12
+1	13
+1	14
+1	15
+EXPLAIN
+SELECT b, c FROM t1 WHERE b = 1 GROUP BY b, c;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	bc	bc	10	NULL	7	Using where; Using index for group-by
+DROP TABLE t1;

mysql-test/t/group_min_max.test

@@ -1018,3 +1018,43 @@ DROP TABLE t;
 
 
 --echo End of 5.0 tests
+#
+# Bug#44821: select distinct on partitioned table returns wrong results
+#
+CREATE TABLE t1 ( a INT, b INT, c INT, KEY bc(b, c) )
+PARTITION BY KEY (a, b) PARTITIONS 3
+;
+
+INSERT INTO t1 VALUES
+(17, 1, -8),
+(3,  1, -7),
+(23, 1, -6),
+(22, 1, -5),
+(11, 1, -4),
+(21, 1, -3),
+(19, 1, -2),
+(30, 1, -1),
+
+(20, 1, 1),
+(16, 1, 2),
+(18, 1, 3),
+(9,  1, 4),
+(15, 1, 5),
+(28, 1, 6),
+(29, 1, 7),
+(25, 1, 8),
+(10, 1, 9),
+(13, 1, 10),
+(27, 1, 11),
+(24, 1, 12),
+(12, 1, 13),
+(26, 1, 14),
+(14, 1, 15)
+;
+
+SELECT b, c FROM t1 WHERE b = 1 GROUP BY b, c;
+
+EXPLAIN
+SELECT b, c FROM t1 WHERE b = 1 GROUP BY b, c;
+
+DROP TABLE t1;

sql/opt_range.cc

@@ -8556,7 +8556,7 @@ int QUICK_RANGE_SELECT::get_next_prefix(uint prefix_length,
     result= file->read_range_first(last_range->min_keypart_map ? &start_key : 0,
 				   last_range->max_keypart_map ? &end_key : 0,
                                    test(last_range->flag & EQ_RANGE),
-				   sorted);
+				   TRUE);
     if (last_range->flag == (UNIQUE_RANGE | EQ_RANGE))
       last_range= 0;			// Stop searching