bzr commit into mysql-next-mr-bugfixing branch (roy.lyseng:3248)

[Roy Lyseng]

#At file:///home/rl136806/mysql/repo/mysql-review/ based on revid:tor.didriksen@stripped

 3248 Roy Lyseng	2010-09-22
      Refactoring: Make members positions and best_positions of class JOIN
      dynamically allocated instead of fixed-size arrays.
      This saves approx. 20 kbyte memory during optimization and execution
      for normal-sized join operations.
            
      sql/sql_select.cc
        Allocate positions and best_positions dynamically.
            
      sql/sql_select.h
        positions and best_positions (members of class JOIN) defined as
        pointers instead of arrays. Made a derived class of Sql_alloc, so
        operator new can be used instead of alloc().

    modified:
      sql/sql_select.cc
      sql/sql_select.h
=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc	2010-09-22 06:51:45 +0000
+++ b/sql/sql_select.cc	2010-09-22 11:37:38 +0000
@@ -4491,6 +4491,14 @@ make_join_statistics(JOIN *join, TABLE_L
   if (!stat || !stat_ref || !table_vector)
     DBUG_RETURN(1);				// Eom /* purecov: inspected */
 
+  if (!(join->positions=
+        new (join->thd->mem_root) POSITION[table_count+1]))
+    DBUG_RETURN(TRUE);
+
+  if (!(join->best_positions=
+        new (join->thd->mem_root) POSITION[table_count+1]))
+    DBUG_RETURN(TRUE);
+
   join->best_ref=stat_vector;
 
   stat_end=stat+table_count;

=== modified file 'sql/sql_select.h'
--- a/sql/sql_select.h	2010-09-06 17:56:05 +0000
+++ b/sql/sql_select.h	2010-09-22 11:37:38 +0000
@@ -1369,7 +1369,7 @@ enum_nested_loop_state sub_select_sjm(JO
      advance_sj_state() for details.
 */
 
-typedef struct st_position
+typedef struct st_position : public Sql_alloc
 {
   /*
     The "fanout" -  number of output rows that will be produced (after
@@ -1613,7 +1613,7 @@ public:
   */
   ha_rows  fetch_limit;
   /* Finally picked QEP. This is result of join optimization */
-  POSITION best_positions[MAX_TABLES+1];
+  POSITION *best_positions;
 
 /******* Join optimization state members start *******/
   /*
@@ -1623,7 +1623,7 @@ public:
   TABLE_LIST *emb_sjm_nest;
   
   /* Current join optimization state */
-  POSITION positions[MAX_TABLES+1];
+  POSITION *positions;
   
   /*
     Bitmap of nested joins embedding the position at the end of the current 


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