Use JIT flushing of post meta cache.

Author: peterwilsoncc

src/wp-includes/class-wp-query.php

@@ -2473,6 +2473,10 @@ public function get_posts() {
 			$clauses = $this->meta_query->get_sql( 'post', $wpdb->posts, 'ID', $this );
 			$join   .= $clauses['join'];
 			$where  .= $clauses['where'];
+
+			if ( ! wp_cache_get( 'wp_query_meta_query_updated', 'post_meta' ) ) {
+				wp_cache_set_posts_last_changed();
+			}
 		}
 
 		$rand = ( isset( $query_vars['orderby'] ) && 'rand' === $query_vars['orderby'] );

src/wp-includes/default-filters.php

@@ -122,9 +122,9 @@
 }
 
 // Post meta.
-add_action( 'added_post_meta', 'wp_cache_set_posts_last_changed' );
-add_action( 'updated_post_meta', 'wp_cache_set_posts_last_changed' );
-add_action( 'deleted_post_meta', 'wp_cache_set_posts_last_changed' );
+add_action( 'added_post_meta', 'wp_cache_set_needs_meta_query_flush' );
+add_action( 'updated_post_meta', 'wp_cache_set_needs_meta_query_flush' );
+add_action( 'deleted_post_meta', 'wp_cache_set_needs_meta_query_flush' );
 
 // User meta.
 add_action( 'added_user_meta', 'wp_cache_set_users_last_changed' );

src/wp-includes/post.php

@@ -8444,6 +8444,17 @@ function wp_add_trashed_suffix_to_post_name_for_post( $post ) {
  */
 function wp_cache_set_posts_last_changed() {
 	wp_cache_set_last_changed( 'posts' );
+	// Indicate meta query cache is updated for use in WP_Query
+	wp_cache_set( 'wp_query_meta_query_updated', true, 'post_meta' );
+}
+
+/**
+ * Marks the WP_Query cache as needing to be flushed after a meta query change.
+ *
+ * @since 7.0.0
+ */
+function wp_cache_set_needs_meta_query_flush() {
+	wp_cache_delete( 'wp_query_meta_query_updated', 'post_meta' );
 }
 
 /**