[wp-trac] [WordPress Trac] #21900: update_post_meta() returns FALSE when meta_value to be updated is the same

[WordPress Trac]

#21900: update_post_meta() returns FALSE when meta_value to be updated is the same
-----------------------------+--------------------------
 Reporter:  mcbenton         |       Type:  defect (bug)
   Status:  new              |   Priority:  normal
Milestone:  Awaiting Review  |  Component:  General
  Version:  3.4.2            |   Severity:  normal
 Keywords:                   |
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 Since [14564] update_metadata() (wp-includes/meta.php [20435]) in lines
 129-136 checks to see if the meta_value to be updated is the same as the
 value that already exists in the database.  The point of this check,
 presumably, is to prevent running a needless UPDATE query.  That's fine
 and good.

 Currently, if the values are the same the function returns FALSE.  I think
 it should return TRUE in this case.  While I understand that from one
 point of view it should be false, since nothing was actually updated, if
 I'm trying to update my metadata to a certain value, and the end result is
 that the value in the database matches the value I submitted, isn't that a
 win?  In other words, even though no UPDATE query was actually executed,
 the postmeta was "updated" to have the value that was specified in
 update_post_meta().

 Here's an example of when this could be an issue:

 {{{
 function my_plugin_ajax_save_metadata() {
     // create a success flag
     $success = true;
     // $postid passed in via post variables
     $postid = $_POST[ 'postid' ];
     // data fields from post passed in from a serialized array
     parse_str( $_POST[ 'data' ], $fields );
     // my custom post meta fields all have names that begin with _mymeta
     foreach( $fields as $key => $val ) {
         // if a field is one of my meta fields, attempt to update it
         if ( false !== strpos( $key, '_mymeta' ) ) {
             // if $val is the same as what's already in the db, $success
 will be false
             $success = update_post_meta( $postid, $key, $val );
         }
         if ( false === $success ) {
             // uh-oh, update_post_meta failed, need to handle it
             // but updating a meta value to the same value is not really a
 fail
             $message = "Error updating metadata: $key = $val";
             break;
         }
     }
     echo ( $success ) ? 'Success.' : $message;
     exit;
 }
 add_action( 'wp_ajax_save_meta', 'my_plugin_ajax_save_metadata' );
 }}}

 Of course, I could use get_post_meta() to find out if values have changed
 before calling update_post_meta(), but since update_metadata() already
 does this (line 131), it seems wasteful for me to have to do it.

 I guess another alternative would be to return something besides TRUE or
 FALSE when the values are the same, but I'm not sure what that would be.

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Ticket URL: <http://core.trac.wordpress.org/ticket/21900>
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