Optimize the total count queries in REST API

Author: Sukhendu2002

src/wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php

@@ -295,9 +295,10 @@ public function get_items( $request ) {
 			// Out-of-bounds, run the query again without LIMIT for total count.
 			unset( $prepared_args['number'], $prepared_args['offset'] );
 
-			$query                    = new WP_Comment_Query();
-			$prepared_args['count']   = true;
-			$prepared_args['orderby'] = 'none';
+			$query                                      = new WP_Comment_Query();
+			$prepared_args['count']                     = true;
+			$prepared_args['orderby']                   = 'none';
+			$prepared_args['update_comment_meta_cache'] = false;
 
 			$total_comments = $query->query( $prepared_args );
 			$max_pages      = (int) ceil( $total_comments / $request['per_page'] );

src/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-revisions-controller.php

@@ -195,7 +195,13 @@ public function get_items( $request ) {
 			if ( $total_revisions < 1 ) {
 				// Out-of-bounds, run the query again without LIMIT for total count.
 				unset( $query_args['paged'], $query_args['offset'] );
-				$count_query = new WP_Query();
+
+				$count_query                          = new WP_Query();
+				$query_args['fields']                 = 'ids';
+				$query_args['posts_per_page']         = 1;
+				$query_args['update_post_meta_cache'] = false;
+				$query_args['update_post_term_cache'] = false;
+
 				$count_query->query( $query_args );
 
 				$total_revisions = $count_query->found_posts;

src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -464,7 +464,12 @@ static function ( $format ) {
 			// Out-of-bounds, run the query again without LIMIT for total count.
 			unset( $query_args['paged'] );
 
-			$count_query = new WP_Query();
+			$count_query                          = new WP_Query();
+			$query_args['fields']                 = 'ids';
+			$query_args['posts_per_page']         = 1;
+			$query_args['update_post_meta_cache'] = false;
+			$query_args['update_post_term_cache'] = false;
+
 			$count_query->query( $query_args );
 			$total_posts = $count_query->found_posts;
 		}

src/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php

@@ -367,8 +367,10 @@ public function get_items( $request ) {
 		if ( $total_users < 1 ) {
 			// Out-of-bounds, run the query again without LIMIT for total count.
 			unset( $prepared_args['number'], $prepared_args['offset'] );
-			$count_query = new WP_User_Query( $prepared_args );
-			$total_users = $count_query->get_total();
+
+			$prepared_args['number'] = 1;
+			$count_query             = new WP_User_Query( $prepared_args );
+			$total_users             = $count_query->get_total();
 		}
 
 		$response->header( 'X-WP-Total', (int) $total_users );