Bug#119198 fix bug optimizer reverse index scan give incorrect result

Author: srmppn

mysql-test/r/optimizer_reverse_index_range_scan_bug.result

@@ -0,0 +1,67 @@
+#
+# Bug#119198 Reverse index range scan give incorrect result.
+#
+CREATE TABLE temp_table (
+id bigint unsigned NOT NULL AUTO_INCREMENT,
+col1 tinyint unsigned NOT NULL,
+col2 tinyint unsigned NOT NULL,
+PRIMARY KEY (id),
+KEY temp_table_idx01 (col1)
+) ENGINE=InnoDB;
+# 2. Insert Data
+INSERT INTO temp_table (id, col1, col2)
+VALUES (10, 1, 4);
+INSERT INTO temp_table (id, col1, col2)
+VALUES (20, 1, 4);
+# 3. Run Query
+SELECT * FROM temp_table;
+id	col1	col2
+10	1	4
+20	1	4
+# Verify table should contain 2 records id#10, id#20 respectively
+#
+EXPLAIN
+SELECT * FROM temp_table
+WHERE col1 >= 1 AND col1 <= 1
+ORDER BY col1 DESC, id DESC
+LIMIT 1;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	temp_table	NULL	range	temp_table_idx01	temp_table_idx01	1	NULL	2	100.00	Using index condition; Backward index scan
+# Query should use reverse index scan range
+#
+SELECT * FROM temp_table
+WHERE col1 >= 1 AND col1 <= 1
+ORDER BY col1 DESC, id DESC
+LIMIT 1;
+id	col1	col2
+20	1	4
+# Query should return valid result with EQ_RANGE ordering by col1 desc limit 1 which is id#20
+#
+SELECT * FROM temp_table
+WHERE col1 >= 1 AND col1 <= 1
+ORDER BY col1 DESC, id DESC
+LIMIT 2;
+id	col1	col2
+20	1	4
+10	1	4
+# Query should return valid result with EQ_RANGE ordering by col1 desc limit 2 which are id#20, id#10
+#
+SELECT * FROM temp_table
+WHERE col1 >= 0 AND col1 <= 5
+ORDER BY col1 DESC, id DESC
+LIMIT 1;
+id	col1	col2
+20	1	4
+# Query should return valid result with EQ_RANGE ordering by col1 desc limit 1 which is id#20
+#
+SELECT * FROM temp_table
+WHERE col1 >= 0 AND col1 <= 5
+ORDER BY col1 DESC, id DESC
+LIMIT 2;
+id	col1	col2
+20	1	4
+10	1	4
+# Query should return valid result with EQ_RANGE ordering by col1 desc limit 2 which are id#20, id#10
+#
+# 4. Clean up
+DROP TABLE temp_table;

mysql-test/t/optimizer_reverse_index_range_scan_bug.test

@@ -0,0 +1,69 @@
+--source include/have_debug_sync.inc
+
+--echo #
+--echo # Bug#119198 Reverse index range scan give incorrect result.
+--echo #
+
+CREATE TABLE temp_table (
+  id bigint unsigned NOT NULL AUTO_INCREMENT,
+  col1 tinyint unsigned NOT NULL,
+  col2 tinyint unsigned NOT NULL,
+  PRIMARY KEY (id),
+  KEY temp_table_idx01 (col1)
+) ENGINE=InnoDB;
+
+--echo # 2. Insert Data
+
+INSERT INTO temp_table (id, col1, col2)
+VALUES (10, 1, 4);
+
+INSERT INTO temp_table (id, col1, col2)
+VALUES (20, 1, 4);
+
+--echo # 3. Run Query
+--disable_warnings
+SELECT * FROM temp_table;
+--echo # Verify table should contain 2 records id#10, id#20 respectively
+--echo #
+
+
+EXPLAIN
+SELECT * FROM temp_table
+    WHERE col1 >= 1 AND col1 <= 1
+    ORDER BY col1 DESC, id DESC
+    LIMIT 1;
+--enable_warnings
+--echo # Query should use reverse index scan range
+--echo #
+
+
+SELECT * FROM temp_table
+    WHERE col1 >= 1 AND col1 <= 1
+    ORDER BY col1 DESC, id DESC
+    LIMIT 1;
+--echo # Query should return valid result with EQ_RANGE ordering by col1 desc limit 1 which is id#20
+--echo #
+
+SELECT * FROM temp_table
+    WHERE col1 >= 1 AND col1 <= 1
+    ORDER BY col1 DESC, id DESC
+    LIMIT 2;
+--echo # Query should return valid result with EQ_RANGE ordering by col1 desc limit 2 which are id#20, id#10
+--echo #
+
+SELECT * FROM temp_table
+    WHERE col1 >= 0 AND col1 <= 5
+    ORDER BY col1 DESC, id DESC
+    LIMIT 1;
+--echo # Query should return valid result with EQ_RANGE ordering by col1 desc limit 1 which is id#20
+--echo #
+
+SELECT * FROM temp_table
+    WHERE col1 >= 0 AND col1 <= 5
+    ORDER BY col1 DESC, id DESC
+    LIMIT 2;
+--echo # Query should return valid result with EQ_RANGE ordering by col1 desc limit 2 which are id#20, id#10
+--echo #
+
+--echo # 4. Clean up
+DROP TABLE temp_table;

sql/sql_optimizer.cc

@@ -9906,8 +9906,9 @@ static bool make_join_query_block(JOIN *join, Item *cond) {
                   used_index(tab->range_scan()) != MAX_KEY) {
                 const uint ref_key = used_index(tab->range_scan());
                 bool skip_quick;
+                uint used_key_parts = 0;
                 read_direction = test_if_order_by_key(
-                    &join->order, tab->table(), ref_key, nullptr, &skip_quick);
+                    &join->order, tab->table(), ref_key, &used_key_parts, &skip_quick);
                 if (skip_quick) read_direction = 0;
                 /*
                   If the index provides order there is no need to recheck
@@ -9921,7 +9922,7 @@ static bool make_join_query_block(JOIN *join, Item *cond) {
                 if (read_direction == 1 ||
                     (read_direction == -1 &&
                      reverse_sort_possible(tab->range_scan()) &&
-                     !make_reverse(get_used_key_parts(tab->range_scan()),
+                     !make_reverse(std::max(used_key_parts, get_used_key_parts(tab->range_scan())),
                                    tab->range_scan()))) {
                   recheck_reason = DONT_RECHECK;
                 }