Better approach for prelocking of tables for stored routines execution

and some SP-related cleanups.

- We don't have separate stage for calculation of list of tables
  to be prelocked and doing implicit LOCK/UNLOCK any more.
  Instead we calculate this list at open_tables() and do implicit
  LOCK in lock_tables() (and UNLOCK in close_thread_tables()).
  Also now we support cases when same table (with same alias) is
  used several times in the same query in SP.

- Cleaned up execution of SP. Moved all common code which handles
  LEX and does preparations before statement execution or complex
  expression evaluation to auxilary sp_lex_keeper class. Now 
  all statements in SP (and corresponding instructions) that
  evaluate expression which can contain subquery have their
  own LEX.

1 files changed, 6 insertions, 5 deletions

diff --git a/sql/sp_rcontext.h b/sql/sp_rcontext.h
index 8e818ab76d1..37d718048a0 100644
--- a/sql/sp_rcontext.h
+++ b/sql/sp_rcontext.h
@@ -25,6 +25,7 @@
 struct sp_cond_type;
 class sp_cursor;
 struct sp_pvar;
+class sp_lex_keeper;
 
 #define SP_HANDLER_NONE      0
 #define SP_HANDLER_EXIT      1
@@ -164,7 +165,7 @@ class sp_rcontext : public Sql_alloc
   restore_variables(uint fp);
 
   void
-  push_cursor(LEX *lex);
+  push_cursor(sp_lex_keeper *lex_keeper);
 
   void
   pop_cursors(uint count);
@@ -207,8 +208,8 @@ class sp_cursor : public Sql_alloc
 {
 public:
 
-  sp_cursor(LEX *lex)
-    : m_lex(lex), m_prot(NULL), m_isopen(0), m_current_row(NULL)
+  sp_cursor(sp_lex_keeper *lex_keeper)
+    : m_lex_keeper(lex_keeper), m_prot(NULL), m_isopen(0), m_current_row(NULL)
   {
     /* Empty */
   }
@@ -220,7 +221,7 @@ public:
 
   // We have split this in two to make it easy for sp_instr_copen
   // to reuse the sp_instr::exec_stmt() code.
-  LEX *
+  sp_lex_keeper *
   pre_open(THD *thd);
   void
   post_open(THD *thd, my_bool was_opened);
@@ -240,7 +241,7 @@ public:
 private:
 
   MEM_ROOT m_mem_root;		// My own mem_root
-  LEX *m_lex;
+  sp_lex_keeper *m_lex_keeper;
   Protocol_cursor *m_prot;
   my_bool m_isopen;
   my_bool m_nseof;		// Original no_send_eof