Automatic merge.

mysql-test/r/subselect4.result

@@ -1190,6 +1190,54 @@ set @@optimizer_switch='materialization=off,semijoin=on';
 set @@optimizer_switch=@save_optimizer_switch;
 drop table t1, t2;
 #
+# LP BUG#777691 Wrong result with subqery in select list and subquery cache=off in maria-5.3
+#
+CREATE TABLE t1 ( f1 varchar(32)) ;
+INSERT INTO t1 VALUES ('b'),('x'),('c'),('x');
+CREATE TABLE t2 ( f2 int, f3 varchar(32)) ;
+INSERT INTO t2 VALUES (1,'x');
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch='materialization=off,in_to_exists=on,subquery_cache=off';
+EXPLAIN
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	
+2	DEPENDENT SUBQUERY	t2	system	NULL	NULL	NULL	NULL	1	
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+f1	max_f2
+b	NULL
+x	1
+c	NULL
+x	1
+set @@optimizer_switch='materialization=on,in_to_exists=off,subquery_cache=off';
+EXPLAIN
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	
+2	DEPENDENT SUBQUERY	t2	system	NULL	NULL	NULL	NULL	1	
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+f1	max_f2
+b	NULL
+x	1
+c	NULL
+x	1
+set @@optimizer_switch='materialization=off,in_to_exists=on,subquery_cache=off';
+Even when t2 is not constant table, the result must be the same.
+INSERT INTO t2 VALUES (2,'y');
+EXPLAIN
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	
+2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+f1	max_f2
+b	NULL
+x	1
+c	NULL
+x	1
+set @@optimizer_switch=@save_optimizer_switch;
+drop table t1, t2;
+#
 # LP BUG#641203 Query returns rows where no result is expected (impossible WHERE)
 #
 CREATE TABLE t1 (c1 varchar(1) DEFAULT NULL);

mysql-test/t/subselect4.test

@@ -964,6 +964,40 @@ WHERE (t2.pk = t1.pk) AND t2.pk IN (SELECT f2 FROM t1);
 -- echo set @@optimizer_switch='materialization=off,semijoin=on';
 
 
+set @@optimizer_switch=@save_optimizer_switch;
+
+drop table t1, t2;
+
+
+--echo #
+--echo # LP BUG#777691 Wrong result with subqery in select list and subquery cache=off in maria-5.3
+--echo #
+
+CREATE TABLE t1 ( f1 varchar(32)) ;
+INSERT INTO t1 VALUES ('b'),('x'),('c'),('x');
+
+CREATE TABLE t2 ( f2 int, f3 varchar(32)) ;
+INSERT INTO t2 VALUES (1,'x');
+
+set @save_optimizer_switch=@@optimizer_switch;
+set @@optimizer_switch='materialization=off,in_to_exists=on,subquery_cache=off';
+
+EXPLAIN
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+
+set @@optimizer_switch='materialization=on,in_to_exists=off,subquery_cache=off';
+EXPLAIN
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+
+set @@optimizer_switch='materialization=off,in_to_exists=on,subquery_cache=off';
+--echo Even when t2 is not constant table, the result must be the same.
+INSERT INTO t2 VALUES (2,'y');
+EXPLAIN
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+SELECT t1.f1, ( SELECT MAX( f2 ) FROM t2 WHERE t2.f3 = t1.f1 ) as max_f2 FROM t1;
+
 set @@optimizer_switch=@save_optimizer_switch;
 
 drop table t1, t2;

sql/item_subselect.h

@@ -1131,11 +1131,18 @@ class subselect_partial_match_engine : public subselect_engine
   /* A list of equalities between each pair of IN operands. */
   List<Item> *equi_join_conds;
   /*
-    If there is a row, such that all its NULL-able components are NULL, this
-    member is set to the number of covered columns. If there is no covering
-    row, then this is 0.
+    True if there is an all NULL row in tmp_table. If so, then if there is
+    no complete match, there is a guaranteed partial match.
   */
-  uint covering_null_row_width;
+  bool has_covering_null_row;
+
+  /*
+    True if all nullable columns of tmp_table consist of only NULL values.
+    If so, then if there is a match in the non-null columns, there is a
+    guaranteed partial match.
+  */
+  bool has_covering_null_columns;
+
 protected:
   virtual bool partial_match()= 0;
 public:
@@ -1144,7 +1151,8 @@ class subselect_partial_match_engine : public subselect_engine
                                  TABLE *tmp_table_arg, Item_subselect *item_arg,
                                  select_result_interceptor *result_arg,
                                  List<Item> *equi_join_conds_arg,
-                                 uint covering_null_row_width_arg);
+                                 bool has_covering_null_row_arg,
+                                 bool has_covering_null_columns_arg);
   int prepare() { return 0; }
   int exec();
   void fix_length_and_dec(Item_cache**) {}
@@ -1191,11 +1199,6 @@ class subselect_rowid_merge_engine: public subselect_partial_match_engine
     outer reference.
   */
   MY_BITMAP matching_outer_cols;
-  /*
-    Columns that consist of only NULLs. Such columns match any value.
-    Computed once per query execution.
-  */
-  MY_BITMAP null_only_columns;
   /*
     Indexes of row numbers, sorted by <column_value, row_number>. If an
     index may contain NULLs, the NULLs are stored efficiently in a bitmap.
@@ -1205,13 +1208,13 @@ class subselect_rowid_merge_engine: public subselect_partial_match_engine
     non-NULL columns, it is contained in keys[0].
   */
   Ordered_key **merge_keys;
-  /* The number of elements in keys. */
-  uint keys_count;
+  /* The number of elements in merge_keys. */
+  uint merge_keys_count;
   /*
     An index on all non-NULL columns of 'tmp_table'. The index has the
     logical form: <[v_i1 | ... | v_ik], rownum>. It allows to find the row
     number where the columns c_i1,...,c1_k contain the values v_i1,...,v_ik.
-    If such an index exists, it is always the first element of 'keys'.
+    If such an index exists, it is always the first element of 'merge_keys'.
   */
   Ordered_key *non_null_key;
   /*
@@ -1236,15 +1239,17 @@ class subselect_rowid_merge_engine: public subselect_partial_match_engine
 public:
   subselect_rowid_merge_engine(THD *thd_arg,
                                subselect_uniquesubquery_engine *engine_arg,
-                               TABLE *tmp_table_arg, uint keys_count_arg,
-                               uint covering_null_row_width_arg,
+                               TABLE *tmp_table_arg, uint merge_keys_count_arg,
+                               bool has_covering_null_row_arg,
+                               bool has_covering_null_columns_arg,
                                Item_subselect *item_arg,
                                select_result_interceptor *result_arg,
                                List<Item> *equi_join_conds_arg)
     :subselect_partial_match_engine(thd_arg, engine_arg, tmp_table_arg,
                                     item_arg, result_arg, equi_join_conds_arg,
-                                    covering_null_row_width_arg),
-    keys_count(keys_count_arg), non_null_key(NULL)
+                                    has_covering_null_row_arg,
+                                    has_covering_null_columns_arg),
+    merge_keys_count(merge_keys_count_arg), non_null_key(NULL)
   {}
   ~subselect_rowid_merge_engine();
   bool init(MY_BITMAP *non_null_key_parts, MY_BITMAP *partial_match_key_parts);
@@ -1263,7 +1268,8 @@ class subselect_table_scan_engine: public subselect_partial_match_engine
                               TABLE *tmp_table_arg, Item_subselect *item_arg,
                               select_result_interceptor *result_arg,
                               List<Item> *equi_join_conds_arg,
-                              uint covering_null_row_width_arg);
+                              bool has_covering_null_row_arg,
+                              bool has_covering_null_columns_arg);
   void cleanup();
   virtual enum_engine_type engine_type() { return TABLE_SCAN_ENGINE; }
 };

sql/sql_select.cc

@@ -14651,14 +14651,6 @@ do_select(JOIN *join,List<Item> *fields,TABLE *table,Procedure *procedure)
       {
         List<Item> *columns_list= (procedure ? &join->procedure_fields_list :
                                    fields);
-        /*
-          With implicit grouping all fields of special row produced for an
-          empty result are NULL. See return_zero_rows() for the same behavior.
-        */
-        TABLE_LIST *table;
-        List_iterator_fast<TABLE_LIST> li(join->select_lex->leaf_tables);
-        while ((table= li++))
-          mark_as_null_row(table->table);
         rc= join->result->send_data(*columns_list) > 0;
       }
     }