[wp-trac] [WordPress Trac] #35816: Add "after_get_posts" action to `WP_Query::get_posts()`

[WordPress Trac]

#35816: Add "after_get_posts" action to `WP_Query::get_posts()`
---------------------------+--------------------------
 Reporter:  stevegrunwell  |       Owner:
     Type:  defect (bug)   |      Status:  new
 Priority:  normal         |   Milestone:  4.5
Component:  Query          |     Version:  trunk
 Severity:  normal         |  Resolution:
 Keywords:                 |     Focuses:  performance
---------------------------+--------------------------

Comment (by boonebgorges):

 @lpawlik This is a promising technique. But it doesn't distinguish between
 multiple instances of `WP_Query` existing at the same time. Say you have
 two posts in two categories, p1/c1 and p2/c2. Now do this:

 {{{
 $q = new WP_Query( array( 'p' => $p1 ) );
 while ( $q->have_posts() ) {
     $q->the_post();

     $nested_q = new WP_Query( array( 'p' => $p2 ) );
     while ( $nested_q->have_posts() ) {
         $nested_q->have_posts();

         get_term_meta( $c2, 'foo' );
     }
 }
 }}}

 That call to `get_term_meta()` should only prime the cache for the terms
 belonging to `$nested_q` - ie, $c2 - and not those belonging to the parent
 query - ie, $c1. (If you're not convinced by the nested queries, imagine a
 dozen queries in serial.)

 Your approach could be adapted, by indexing post IDs in the
 `WP_Lazy_Loader` object by an identifier that is unique to the query
 instance. Something like:

 {{{
     ...
     if ( $q['update_post_term_cache'] ) {
         handle_lazy_loads( $this );
     }
     ...

 class WP_Lazy Loader {
     ...
     function add_posts( WP_Query $query ) {
         $key = _wp_filter_build_unique_id( array( $query, '' ) );
         $this->queries[ $key ] = $posts;
     }
     ....

     function lazyload_term_meta( $check, $term_id ) {
         ...
         foreach ( $this->queries as $qposts ) {
             // If term belongs to one of the posts, then prime cache for
 all post terms in the query
         }

         ...
     }
 }}}

 Does this seem right to you?

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Ticket URL: <https://core.trac.wordpress.org/ticket/35816#comment:5>
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