BUG#849763: Wrong result with second execution of prepared statement with semijoin + view

- The problem was that Item_direct_view_ref and its embedded Item_field were getting incorrect
  value of item->used_tables() after fix_fields() in the second and subsequent EXECUTE.
- Made relevant fixes in Item_field::fix_fields() and find_field_in_tables(), so that the 
  Item_field gets the correct attributes.

mysql-test/r/subselect_sj2.result

@@ -747,4 +747,21 @@ LEFT JOIN t2 AS SQ4_alias3 ON SQ4_alias3.f10
 GROUP BY field2;
 field2
 drop table t1, t2, t3;
+#
+# BUG#849763: Wrong result with second execution of prepared statement with semijoin + view
+#
+CREATE TABLE t1 ( c varchar(1)) engine=innodb;
+INSERT INTO t1 VALUES ('r');
+CREATE TABLE t2 ( a integer, b varchar(1), c varchar(1)) engine=innodb;
+INSERT INTO t2 VALUES (1,'r','r');
+CREATE OR REPLACE VIEW v1 AS SELECT * FROM t1;
+PREPARE st1 FROM 'SELECT * FROM t2 WHERE a = SOME (SELECT a FROM v1 WHERE v1.c = t2.c)';
+EXECUTE st1;
+a	b	c
+1	r	r
+EXECUTE st1;
+a	b	c
+1	r	r
+DROP VIEW v1;
+DROP TABLE t1, t2;
 set optimizer_switch=@subselect_sj2_tmp;

mysql-test/r/subselect_sj2_jcl6.result

@@ -758,6 +758,23 @@ LEFT JOIN t2 AS SQ4_alias3 ON SQ4_alias3.f10
 GROUP BY field2;
 field2
 drop table t1, t2, t3;
+#
+# BUG#849763: Wrong result with second execution of prepared statement with semijoin + view
+#
+CREATE TABLE t1 ( c varchar(1)) engine=innodb;
+INSERT INTO t1 VALUES ('r');
+CREATE TABLE t2 ( a integer, b varchar(1), c varchar(1)) engine=innodb;
+INSERT INTO t2 VALUES (1,'r','r');
+CREATE OR REPLACE VIEW v1 AS SELECT * FROM t1;
+PREPARE st1 FROM 'SELECT * FROM t2 WHERE a = SOME (SELECT a FROM v1 WHERE v1.c = t2.c)';
+EXECUTE st1;
+a	b	c
+1	r	r
+EXECUTE st1;
+a	b	c
+1	r	r
+DROP VIEW v1;
+DROP TABLE t1, t2;
 set optimizer_switch=@subselect_sj2_tmp;
 set join_cache_level=default;
 show variables like 'join_cache_level';

mysql-test/t/subselect_sj2.test

@@ -944,4 +944,22 @@ WHERE alias2.f11 IN (
 GROUP BY field2;
 drop table t1, t2, t3;
 
+--echo #
+--echo # BUG#849763: Wrong result with second execution of prepared statement with semijoin + view
+--echo #
+CREATE TABLE t1 ( c varchar(1)) engine=innodb;
+INSERT INTO t1 VALUES ('r');
+
+CREATE TABLE t2 ( a integer, b varchar(1), c varchar(1)) engine=innodb;
+INSERT INTO t2 VALUES (1,'r','r');
+
+CREATE OR REPLACE VIEW v1 AS SELECT * FROM t1;
+
+PREPARE st1 FROM 'SELECT * FROM t2 WHERE a = SOME (SELECT a FROM v1 WHERE v1.c = t2.c)';
+EXECUTE st1;
+EXECUTE st1;
+
+DROP VIEW v1;
+DROP TABLE t1, t2;
+
 set optimizer_switch=@subselect_sj2_tmp;

sql/item.cc

@@ -4648,6 +4648,7 @@ bool Item_field::fix_fields(THD *thd, Item **reference)
     if (!outer_fixed && cached_table && cached_table->select_lex &&
         context->select_lex &&
         cached_table->select_lex != context->select_lex &&
+        !context->select_lex->is_merged_child_of(cached_table->select_lex) &&
         is_outer_table(cached_table, context->select_lex))
     {
       int ret;

sql/sql_base.cc

@@ -6447,11 +6447,25 @@ find_field_in_tables(THD *thd, Item_ident *item,
       {
         SELECT_LEX *current_sel= thd->lex->current_select;
         SELECT_LEX *last_select= table_ref->select_lex;
+        bool all_merged= TRUE;
+        for (SELECT_LEX *sl= current_sel; sl && sl!=last_select;
+             sl=sl->outer_select())
+        {
+          Item *subs= sl->master_unit()->item;
+          if (subs->type() == Item::SUBSELECT_ITEM && 
+             ((Item_subselect*)subs)->substype() == Item_subselect::IN_SUBS &&
+             ((Item_in_subselect*)subs)->in_strategy & SUBS_SEMI_JOIN)
+          {
+            continue;
+          }
+          all_merged= FALSE;
+          break;
+        }
         /*
           If the field was an outer referencee, mark all selects using this
           sub query as dependent on the outer query
         */
-        if (current_sel != last_select)
+        if (!all_merged && current_sel != last_select)
         {
           mark_select_range_as_dependent(thd, last_select, current_sel,
                                          found, *ref, item);

sql/sql_lex.cc

@@ -3622,6 +3622,47 @@ bool st_select_lex::save_prep_leaf_tables(THD *thd)
 }
 
 
+/*
+  Return true if this select_lex has been converted into a semi-join nest
+  within 'ancestor'.
+
+  We need a loop to check this because there could be several nested
+  subselects, like
+
+    SELECT ... FROM grand_parent 
+      WHERE expr1 IN (SELECT ... FROM parent 
+                        WHERE expr2 IN ( SELECT ... FROM child)
+
+  which were converted into:
+  
+    SELECT ... 
+    FROM grand_parent SEMI_JOIN (parent JOIN child) 
+    WHERE 
+      expr1 AND expr2
+
+  In this case, both parent and child selects were merged into the parent.
+*/
+
+bool st_select_lex::is_merged_child_of(st_select_lex *ancestor)
+{
+  bool all_merged= TRUE;
+  for (SELECT_LEX *sl= this; sl && sl!=ancestor;
+       sl=sl->outer_select())
+  {
+    Item *subs= sl->master_unit()->item;
+    if (subs && subs->type() == Item::SUBSELECT_ITEM && 
+       ((Item_subselect*)subs)->substype() == Item_subselect::IN_SUBS &&
+       ((Item_in_subselect*)subs)->in_strategy & SUBS_SEMI_JOIN)
+    {
+      continue;
+    }
+    all_merged= FALSE;
+    break;
+  }
+  return all_merged;
+}
+
+
 /**
   A routine used by the parser to decide whether we are specifying a full
   partitioning or if only partitions to add or to split.

sql/sql_lex.h

@@ -907,7 +907,7 @@ class st_select_lex: public st_select_lex_node
 
   bool save_leaf_tables(THD *thd);
   bool save_prep_leaf_tables(THD *thd);
-
+  bool is_merged_child_of(st_select_lex *ancestor);
 private:  
   /* current index hint kind. used in filling up index_hints */
   enum index_hint_type current_index_hint_type;