Small cleanup in code handling stored routines/table prelocking.

Use lazy initialization for Query_tables_list::sroutines hash.
This step should significantly decrease amount of memory consumed
by stored routines as we no longer will allocate chunk of memory
required for this HASH for each statement in routine.


include/hash.h:
  Introduced auxillary hash_init_opt() macro which simplifies
  lazy initialization of HASH objects.
sql/sp.cc:
  Use lazy initialization for Query_tables_list::sroutines hash.
  This step should significantly decrease amount of memory consumed
  by stored routines as we no longer will allocate chunk of memory
  required for this HASH for each statement in routine.
sql/sql_lex.cc:
  Use lazy initialization for Query_tables_list::sroutines hash.
  This step should significantly decrease amount of memory consumed
  by stored routines as we no longer will allocate chunk of memory
  required for this HASH for each statement in routine.
sql/sql_lex.h:
  Updated comment describing Query_tables_list::sroutines to
  reflect that now we are use lazy initialization for this hash.
  Added constant for initial size of this hash.

4 files changed, 21 insertions, 2 deletions

diff --git a/include/hash.h b/include/hash.h
index 8f5ff21ae5e..4d6ee77fa0c 100644
--- a/include/hash.h
+++ b/include/hash.h
@@ -65,6 +65,8 @@ my_bool hash_check(HASH *hash);			/* Only in debug library */
 
 #define hash_clear(H) bzero((char*) (H),sizeof(*(H)))
 #define hash_inited(H) ((H)->array.buffer != 0)
+#define hash_init_opt(A,B,C,D,E,F,G,H) \
+          (!hash_inited(A) && _hash_init(A,B,C,D,E,F,G, H CALLER_INFO))
 
 #ifdef	__cplusplus
 }
diff --git a/sql/sp.cc b/sql/sp.cc
index 49dbed79fe5..5d5c2b148d4 100644
--- a/sql/sp.cc
+++ b/sql/sp.cc
@@ -1369,6 +1369,10 @@ static bool add_used_routine(LEX *lex, Query_arena *arena,
                              const LEX_STRING *key,
                              TABLE_LIST *belong_to_view)
 {
+  hash_init_opt(&lex->sroutines, system_charset_info,
+                Query_tables_list::START_SROUTINES_HASH_SIZE,
+                0, 0, sp_sroutine_key, 0, 0);
+
   if (!hash_search(&lex->sroutines, (byte *)key->str, key->length))
   {
     Sroutine_hash_entry *rn=
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 405f576ac04..24b9766a658 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -1634,9 +1634,18 @@ void Query_tables_list::reset_query_tables_list(bool init)
   query_tables_last= &query_tables;
   query_tables_own_last= 0;
   if (init)
-    hash_init(&sroutines, system_charset_info, 0, 0, 0, sp_sroutine_key, 0, 0);
+  {
+    /*
+      We delay real initialization of hash (and therefore related
+      memory allocation) until first insertion into this hash.
+    */
+    hash_clear(&sroutines);
+  }
   else if (sroutines.records)
+  {
+    /* Non-zero sroutines.records means that hash was initialized. */
     my_hash_reset(&sroutines);
+  }
   sroutines_list.empty();
   sroutines_list_own_last= sroutines_list.next;
   sroutines_list_own_elements= 0;
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 378f968118e..bfe7d9518f3 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -742,7 +742,11 @@ public:
     0 - indicates that this query does not need prelocking.
   */
   TABLE_LIST **query_tables_own_last;
-  /* Set of stored routines called by statement. */
+  /*
+    Set of stored routines called by statement.
+    (Note that we use lazy-initialization for this hash).
+  */
+  enum { START_SROUTINES_HASH_SIZE= 16 };
   HASH sroutines;
   /*
     List linking elements of 'sroutines' set. Allows you to add new elements