BUG#901399: Wrong result (extra row) with semijoin=ON, materialization=OFF, optimizer_prune_level=0

- Correctly handle plan refinement stage for LooseScan plans: run create_ref_for_key() if LooseScan 
  plan includes a ref access, and if we don't have any fixed key components, switch to a full index scan.

mysql-test/r/subselect3.result

@@ -1274,11 +1274,11 @@ insert into t1 select A.a, B.a, 'filler' from t0 A, t0 B;
 create table t2 as select * from t1;
 explain select * from t2 where a in (select b from t1 where a=3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	range	a	a	5	NULL	8	Using where; Using index; LooseScan
+1	PRIMARY	t1	ref	a	a	5	const	8	Using index; LooseScan
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	100	Using where; Using join buffer (flat, BNL join)
 explain select * from t2 where (b,a) in (select a,b from t1 where a=3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	range	a	a	5	NULL	8	Using where; Using index; LooseScan
+1	PRIMARY	t1	ref	a	a	5	const	8	Using index; LooseScan
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	100	Using where; Using join buffer (flat, BNL join)
 drop table t1,t2;
 set @@optimizer_switch=@save_optimizer_switch;

mysql-test/r/subselect3_jcl6.result

@@ -1283,11 +1283,11 @@ insert into t1 select A.a, B.a, 'filler' from t0 A, t0 B;
 create table t2 as select * from t1;
 explain select * from t2 where a in (select b from t1 where a=3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	range	a	a	5	NULL	8	Using where; Using index; LooseScan
+1	PRIMARY	t1	ref	a	a	5	const	8	Using index; LooseScan
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	100	Using where; Using join buffer (flat, BNL join)
 explain select * from t2 where (b,a) in (select a,b from t1 where a=3);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	range	a	a	5	NULL	8	Using where; Using index; LooseScan
+1	PRIMARY	t1	ref	a	a	5	const	8	Using index; LooseScan
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	100	Using where; Using join buffer (flat, BNL join)
 drop table t1,t2;
 set @@optimizer_switch=@save_optimizer_switch;

mysql-test/r/subselect_sj.result

@@ -2149,4 +2149,31 @@ a	a
 SET optimizer_prune_level=DEFAULT;
 SET optimizer_switch=@tmp_optimizer_switch;
 DROP TABLE t1,t2,t3,t4;
+#
+# BUG#901399: Wrong result (extra row) with semijoin=ON, materialization=OFF, optimizer_prune_level=0
+#
+set @opl_901399= @@optimizer_prune_level;
+set @os_091399= @@optimizer_switch;
+SET optimizer_prune_level=0;
+SET optimizer_switch = 'materialization=off';
+CREATE TABLE t1 ( c INT ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES
+(0),(1),(2),(3),(4),(5),
+(6),(7),(8),(9),(10),(11),(12);
+CREATE TABLE t2 ( a INT, b INT, KEY(a)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (3,20),(2,21),(3,22);
+SELECT *
+FROM t1 AS alias1, t1 AS alias2
+WHERE ( alias1.c, alias2.c )
+IN (
+SELECT alias3.a, alias3.a
+FROM t2 AS alias3, t2 alias4
+WHERE alias3.b = alias4.b
+);
+c	c
+2	2
+3	3
+set optimizer_prune_level= @opl_901399;
+set optimizer_switch= @os_091399;
+DROP TABLE t1,t2;
 set optimizer_switch=@subselect_sj_tmp;

mysql-test/r/subselect_sj_jcl6.result

@@ -2155,6 +2155,33 @@ a	a
 SET optimizer_prune_level=DEFAULT;
 SET optimizer_switch=@tmp_optimizer_switch;
 DROP TABLE t1,t2,t3,t4;
+#
+# BUG#901399: Wrong result (extra row) with semijoin=ON, materialization=OFF, optimizer_prune_level=0
+#
+set @opl_901399= @@optimizer_prune_level;
+set @os_091399= @@optimizer_switch;
+SET optimizer_prune_level=0;
+SET optimizer_switch = 'materialization=off';
+CREATE TABLE t1 ( c INT ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES
+(0),(1),(2),(3),(4),(5),
+(6),(7),(8),(9),(10),(11),(12);
+CREATE TABLE t2 ( a INT, b INT, KEY(a)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (3,20),(2,21),(3,22);
+SELECT *
+FROM t1 AS alias1, t1 AS alias2
+WHERE ( alias1.c, alias2.c )
+IN (
+SELECT alias3.a, alias3.a
+FROM t2 AS alias3, t2 alias4
+WHERE alias3.b = alias4.b
+);
+c	c
+2	2
+3	3
+set optimizer_prune_level= @opl_901399;
+set optimizer_switch= @os_091399;
+DROP TABLE t1,t2;
 set optimizer_switch=@subselect_sj_tmp;
 #
 # BUG#49129: Wrong result with IN-subquery with join_cache_level=6 and firstmatch=off

mysql-test/t/subselect_sj.test

@@ -1967,5 +1967,34 @@ SET optimizer_switch=@tmp_optimizer_switch;
 
 DROP TABLE t1,t2,t3,t4;
 
+--echo #
+--echo # BUG#901399: Wrong result (extra row) with semijoin=ON, materialization=OFF, optimizer_prune_level=0
+--echo #
+set @opl_901399= @@optimizer_prune_level;
+set @os_091399= @@optimizer_switch;
+SET optimizer_prune_level=0;
+SET optimizer_switch = 'materialization=off';
+
+CREATE TABLE t1 ( c INT ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES
+  (0),(1),(2),(3),(4),(5),
+  (6),(7),(8),(9),(10),(11),(12);
+CREATE TABLE t2 ( a INT, b INT, KEY(a)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (3,20),(2,21),(3,22);
+
+SELECT *
+FROM t1 AS alias1, t1 AS alias2
+WHERE ( alias1.c, alias2.c )
+  IN (
+      SELECT alias3.a, alias3.a
+        FROM t2 AS alias3, t2 alias4
+        WHERE alias3.b = alias4.b
+     );
+set optimizer_prune_level= @opl_901399;
+set optimizer_switch= @os_091399;
+
+DROP TABLE t1,t2;
+
+
 # The following command must be the last one the file 
 set optimizer_switch=@subselect_sj_tmp;

sql/sql_select.cc

@@ -61,7 +61,7 @@ static bool sort_and_filter_keyuse(THD *thd, DYNAMIC_ARRAY *keyuse,
                                    bool skip_unprefixed_keyparts);
 static int sort_keyuse(KEYUSE *a,KEYUSE *b);
 static bool create_ref_for_key(JOIN *join, JOIN_TAB *j, KEYUSE *org_keyuse,
-			       table_map used_tables);
+			       bool allow_full_scan, table_map used_tables);
 void best_access_path(JOIN *join, JOIN_TAB *s, 
                              table_map remaining_tables, uint idx, 
                              bool disable_jbuf, double record_count,
@@ -3313,7 +3313,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
 	        s->type= JT_CONST;
 	        join->const_table_map|=table->map;
 	        set_position(join,const_count++,s,start_keyuse);
-	        if (create_ref_for_key(join, s, start_keyuse,
+	        if (create_ref_for_key(join, s, start_keyuse, FALSE,
 				       found_const_table_map))
                   goto error;
 	        if ((tmp=join_read_const_table(s,
@@ -7068,15 +7068,21 @@ get_best_combination(JOIN *join)
 
     if (j->type == JT_SYSTEM)
       goto loop_end;
-    if ( !(keyuse= join->best_positions[tablenr].key) || 
-        (join->best_positions[tablenr].sj_strategy == SJ_OPT_LOOSE_SCAN))
+    if ( !(keyuse= join->best_positions[tablenr].key))
     {
       j->type=JT_ALL;
-      j->index= join->best_positions[tablenr].loosescan_picker.loosescan_key;
       if (tablenr != join->const_tables)
 	join->full_join=1;
     }
-    else if (create_ref_for_key(join, j, keyuse, used_tables))
+
+    /*if (join->best_positions[tablenr].sj_strategy == SJ_OPT_LOOSE_SCAN)
+    {
+      DBUG_ASSERT(!keyuse || keyuse->key ==
+                             join->best_positions[tablenr].loosescan_picker.loosescan_key);
+      j->index= join->best_positions[tablenr].loosescan_picker.loosescan_key;
+    }*/
+    
+    if (keyuse && create_ref_for_key(join, j, keyuse, TRUE, used_tables))
       DBUG_RETURN(TRUE);                        // Something went wrong
 
     if ((j->type == JT_REF || j->type == JT_EQ_REF) &&
@@ -7249,7 +7255,8 @@ static bool are_tables_local(JOIN_TAB *jtab, table_map used_tables)
 }
 
 static bool create_ref_for_key(JOIN *join, JOIN_TAB *j,
-                               KEYUSE *org_keyuse, table_map used_tables)
+                               KEYUSE *org_keyuse, bool allow_full_scan, 
+                               table_map used_tables)
 {
   uint keyparts, length, key;
   TABLE *table;
@@ -7307,6 +7314,14 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j,
       keyuse++;
     } while (keyuse->table == table && keyuse->key == key);
   } /* not ftkey */
+  
+  if (!keyparts && allow_full_scan)
+  {
+    /* It's a LooseIndexScan strategy scanning whole index */
+    j->type= JT_ALL;
+    j->index= key;
+    DBUG_RETURN(FALSE);
+  }
 
   /* set up fieldref */
   j->ref.key_parts= keyparts;
@@ -15188,7 +15203,7 @@ sub_select(JOIN *join,JOIN_TAB *join_tab,bool end_of_records)
         join_tab->loosescan_match_tab->found_match)
     {
       KEY *key= join_tab->table->key_info + join_tab->index;
-      key_copy(join_tab->loosescan_buf, info->record, key, 
+      key_copy(join_tab->loosescan_buf, join_tab->table->record[0], key, 
                join_tab->loosescan_key_len);
       skip_over= TRUE;
     }
@@ -17571,7 +17586,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit_arg,
           while (keyuse->key != new_ref_key && keyuse->table == tab->table)
             keyuse++;
 
-          if (create_ref_for_key(tab->join, tab, keyuse, 
+          if (create_ref_for_key(tab->join, tab, keyuse, FALSE,
                                  tab->join->const_table_map))
             goto use_filesort;
 

sql/sql_select.h

@@ -296,7 +296,16 @@ typedef struct st_join_table {
   double        partial_join_cardinality;
 
   table_map	dependent,key_dependent;
-  uint		use_quick,index;
+  /*
+     1 - use quick select
+     2 - use "Range checked for each record"
+  */
+  uint		use_quick;
+  /*
+    Index to use. Note: this is valid only for 'index' access, but not range or
+    ref access.
+  */
+  uint          index;
   uint		status;				///< Save status for cache
   uint		used_fields;
   ulong         used_fieldlength;