From 76fd8c1c2f46da3e06e365a104d6d9f43df8b0c2 Mon Sep 17 00:00:00 2001
From: Sergey Petrunya <psergey@askmonty.org>
Date: Mon, 9 May 2011 11:20:51 +0100
Subject: [PATCH] Change "disable semi-joins in presense of outer joins" check
 to actually check for outer joins (and not for any "t1 SOME_JOIN t2 ON cond"
 syntax).

---
 sql/opt_subselect.cc | 27 +++++++++++++++++++++++++++
 sql/sql_select.h     |  3 ++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc
index c89cfde763c..24727d2f656 100644
--- a/sql/opt_subselect.cc
+++ b/sql/opt_subselect.cc
@@ -601,6 +601,26 @@ bool make_in_exists_conversion(THD *thd, JOIN *join, Item_in_subselect *item)
 }
 
 
+bool check_for_outer_joins(List<TABLE_LIST> *join_list)
+{
+  TABLE_LIST *table;
+  NESTED_JOIN *nested_join;
+  List_iterator<TABLE_LIST> li(*join_list);
+  while ((table= li++))
+  {
+    if ((nested_join= table->nested_join))
+    {
+      if (check_for_outer_joins(&nested_join->join_list))
+        return TRUE;
+    }
+    
+    if (table->outer_join)
+      return TRUE;
+  }
+  return FALSE;
+}
+
+
 /*
   Convert semi-join subquery predicates into semi-join join nests
 
@@ -685,6 +705,7 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
   
   // Temporary measure: disable semi-joins when they are together with outer
   // joins.
+  /*
   for (TABLE_LIST *tbl= join->select_lex->leaf_tables; tbl; tbl=tbl->next_leaf)
   {
     TABLE_LIST *embedding= tbl->embedding;
@@ -695,6 +716,12 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
       arena= thd->activate_stmt_arena_if_needed(&backup);
       goto skip_conversion;
     }
+  }*/
+  if (check_for_outer_joins(join->join_list))
+  {
+    in_subq= join->sj_subselects.front();
+    arena= thd->activate_stmt_arena_if_needed(&backup);
+    goto skip_conversion;
   }
 
   //dump_TABLE_LIST_struct(select_lex, select_lex->leaf_tables);
diff --git a/sql/sql_select.h b/sql/sql_select.h
index 9a5c0494d29..4fbb8121208 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -701,7 +701,8 @@ public:
   /* Tables removed by table elimination. Set to 0 before the elimination. */
   table_map eliminated_tables;
   /*
-     Bitmap of all inner tables from outer joins
+     Bitmap of all inner tables from outer joins (set at start of
+     make_join_statistics)
   */
   table_map outer_join;
   ha_rows  send_records,found_records,examined_rows,row_limit, select_limit;