gistfile1.txt

=== modified file 'sql/sql_array.h'
--- sql/sql_array.h	2013-11-20 11:05:39 +0000
+++ sql/sql_array.h	2014-01-16 12:01:51 +0000
@@ -105,6 +105,21 @@ template <class Elem> class Dynamic_arra
     init(prealloc, increment);
   }
 
+  /*
+    Same as above, but make use of initial buffer provided by the caller. The
+    Dynamic_array will not try to free the initial buffer.
+  */
+  Dynamic_array(char *buffer, uint buffer_elements, uint increment=16)
+  {
+    init_with_buffer(buffer, buffer_elements, increment);
+  }
+
+  void init_with_buffer(char *buffer, uint buffer_elements, uint increment=16)
+  {
+    my_init_dynamic_array2(&array, sizeof(Elem), buffer, buffer_elements,
+                           increment, MYF(0));
+  }
+
   void init(uint prealloc=16, uint increment=16)
   {
     my_init_dynamic_array(&array, sizeof(Elem), prealloc, increment,

=== modified file 'sql/sql_explain.cc'
--- sql/sql_explain.cc	2013-10-16 16:20:20 +0000
+++ sql/sql_explain.cc	2014-01-16 12:09:33 +0000
@@ -23,7 +23,9 @@
 
 
 Explain_query::Explain_query(THD *thd_arg) : 
-  upd_del_plan(NULL), insert_plan(NULL), thd(thd_arg), apc_enabled(false)
+  upd_del_plan(NULL), insert_plan(NULL), 
+  unions(unions_buf, PREALLOC_ELEMS), selects(selects_buf, PREALLOC_ELEMS),
+  thd(thd_arg), apc_enabled(false)
 {
   operations= 0;
 }

=== modified file 'sql/sql_explain.h'
--- sql/sql_explain.h	2013-10-17 13:50:30 +0000
+++ sql/sql_explain.h	2014-01-16 12:08:06 +0000
@@ -259,6 +259,10 @@ class Explain_query : public Sql_alloc
   /* Query "plan" for INSERTs */
   Explain_insert *insert_plan;
 
+  enum { PREALLOC_ELEMS= 4 };
+  char unions_buf[sizeof(void*) * PREALLOC_ELEMS];
+  char selects_buf[sizeof(void*) * PREALLOC_ELEMS];
+
   Dynamic_array<Explain_union*> unions;
   Dynamic_array<Explain_select*> selects;