A fix and a test case for Bug#12736 "Server crash during a select".

The bug was in JOIN::join_free which was wrongly determining that
all joins have been already executed and therefore all used tables
can be closed.


mysql-test/r/subselect_innodb.result:
  - test results fixed (Bug#12736 "Server crash during a select
mysql-test/t/subselect_innodb.test:
  - a test case for Bug#12736 "Server crash during a select": test
  that ha_index_or_rnd_end and mysql_unlock_tables are called
  for all used tables in proper order.
sql/item_subselect.cc:
  - implement subselect_union_engine::is_executed
sql/item_subselect.h:
  - implement Item_subselect::is_evaluated. This function is used
  to check whether we can clean up a non-correlated join of a subquery
  when cleaning up the join of the outer query
sql/sql_lex.h:
  - declare st_select_lex::cleanup_all_joins
sql/sql_select.cc:
  - remove an argument from JOIN::join_free, it's now not used
  - reimplement JOIN::join_free to not unlock tables if there
    is a subquery that has not yet been evaluated. Make sure that the
    new implementation calls ha_index_or_rnd_end for every table in
    the join and inner joins, because all table cursors must be closed
    before mysql_unlock_tables.
sql/sql_select.h:
  - JOIN::join_free signature changed
sql/sql_union.cc:
  - implement a helper method st_select_lex::cleanup_all_joins, which
    recursively walks over a tree of joins and calls cleanup() for
    each join.

1 files changed, 16 insertions, 0 deletions

diff --git a/sql/item_subselect.h b/sql/item_subselect.h
index 5b22930ae1f..f1c99f74498 100644
--- a/sql/item_subselect.h
+++ b/sql/item_subselect.h
@@ -110,6 +110,12 @@ public:
     return eng == 0;
   }
   /*
+    True if this subquery has been already evaluated. Implemented only for
+    single select and union subqueries only.
+  */
+  bool is_evaluated() const;
+
+  /*
     Used by max/min subquery to initialize value presence registration
     mechanism. Engine call this method before rexecution query.
   */
@@ -317,6 +323,7 @@ public:
   virtual void print(String *str)= 0;
   virtual bool change_result(Item_subselect *si, select_subselect *result)= 0;
   virtual bool no_tables()= 0;
+  virtual bool is_executed() const { return FALSE; }
 };
 
 
@@ -342,6 +349,7 @@ public:
   void print (String *str);
   bool change_result(Item_subselect *si, select_subselect *result);
   bool no_tables();
+  bool is_executed() const { return executed; }
 };
 
 
@@ -363,6 +371,7 @@ public:
   void print (String *str);
   bool change_result(Item_subselect *si, select_subselect *result);
   bool no_tables();
+  bool is_executed() const;
 };
 
 
@@ -411,3 +420,10 @@ public:
   int exec();
   void print (String *str);
 };
+
+
+inline bool Item_subselect::is_evaluated() const
+{
+  return engine->is_executed();
+}
+