Bug #73272 Reduce two memset to one memset call for upd_create call.

• Submitted: 11 Jul 2014 6:10
• Modified: 26 Aug 2014 13:08
• Reporter: Fangxin Flou (OCA)
• Status: Closed
• Category: MySQL Server: InnoDB storage engine
• Severity: S5 (Performance)
• Version: 5.6.19
• OS: Any
• CPU Architecture: Any
• Tags: Contribution, innodb, Memory

[11 Jul 2014 6:10] Fangxin Flou

Description:
Reduce two memset to one memset call for upd_create call.

UNIV_INLINE
upd_t*
upd_create(
/*=======*/
        ulint           n,      /*!< in: number of fields */
        mem_heap_t*     heap)   /*!< in: heap from which memory allocated */
{
        upd_t*  update;

        update = (upd_t*) mem_heap_zalloc(heap, sizeof(upd_t));

        update->n_fields = n;
        update->fields = (upd_field_t*)
                mem_heap_zalloc(heap, sizeof(upd_field_t) * n);

        return(update);
}

there is no need to use two mem_heap_zalloc call.

How to repeat:
N/A

Suggested fix:
diff -rc --exclude='*.orig' --exclude=sql_yacc.cc --exclude=sql_yacc.h mysql-5.6.19/storage/innobase/include/row0upd.ic mysql-5.6.19-patched/storage/innobase/include/row0upd.ic
*** mysql-5.6.19/storage/innobase/include/row0upd.ic	2014-05-06 18:45:59.000000000 +0800
--- mysql-5.6.19-patched/storage/innobase/include/row0upd.ic	2014-07-11 14:01:53.000000000 +0800
***************
*** 44,54 ****
  {
  	upd_t*	update;

! 	update = (upd_t*) mem_heap_zalloc(heap, sizeof(upd_t));

  	update->n_fields = n;
! 	update->fields = (upd_field_t*)
! 		mem_heap_zalloc(heap, sizeof(upd_field_t) * n);

  	return(update);
  }
--- 44,56 ----
  {
  	upd_t*	update;

! 	/* update = (upd_t*) mem_heap_zalloc(heap, sizeof(upd_t)); */
! 	update = (upd_t*) mem_heap_zalloc(heap, sizeof(upd_t) + sizeof(upd_field_t) * n);

  	update->n_fields = n;
! 	/* update->fields = (upd_field_t*)
! 		mem_heap_zalloc(heap, sizeof(upd_field_t) * n); */
! 	update->fields = (upd_field_t*)(&update[1]);

  	return(update);
  }

[25 Jul 2014 19:45] Sveta Smirnova

Thank you for the contribution!

[26 Aug 2014 13:08] Daniel Price

Fixed as of the upcoming 5.7.5 release, and here's the changelog entry:

Reduced "mem_heap_zalloc" calls in "upd_create". Only a single call is
necessary to allocate memory for "upd_t". 

Thank you for the bug report.