perf(2meet-data-optimizer): keep WordPress's split query on routed searches

- posts_request only drops SQL_CALC_FOUND_ROWS, but WordPress then treated the request as filtered and selected full post rows through a temporary table; split_the_query now keeps the ID-first split for routed searches when nothing else changed the request, and posts_request_ids drops SQL_CALC_FOUND_ROWS from the split ID query
- Verify: tests/live/run.php router (12/12, IDs-first request, found_posts == native); dev36 fe.sh price 589→340 ms, price__asc 961→427 ms, rating__desc 1724→872 ms, hourly_rate__desc 855→884 ms (was 1206)
- PR: PR-062b

includes/query/class-tmdo-post-query-router.php

@@ -92,6 +92,8 @@ class TMDO_Post_Query_Router {
 		add_filter( 'posts_where', array( $this, 'posts_where' ), 10, 2 );
 		add_filter( 'posts_orderby', array( $this, 'posts_orderby' ), 10, 2 );
 		add_filter( 'posts_request', array( $this, 'posts_request' ), 10, 2 );
+		add_filter( 'split_the_query', array( $this, 'split_the_query' ), 10, 4 );
+		add_filter( 'posts_request_ids', array( $this, 'posts_request' ), 10, 2 );
 		add_filter( 'found_posts_query', array( $this, 'found_posts_query' ), 10, 2 );
 	}
 
@@ -338,12 +340,37 @@ class TMDO_Post_Query_Router {
 		if ( ! $routed || false === strpos( $request, 'SQL_CALC_FOUND_ROWS' ) ) {
 			return $request;
 		}
-		$request = preg_replace( '/\bSQL_CALC_FOUND_ROWS\s+/', '', $request, 1 );
+		$request = self::without_found_rows( $request );
 		$matches = preg_replace( '/\s+LIMIT\s+\d+(\s*,\s*\d+)?\s*$/i', '', $request );
 		$query->set( self::COUNT_VAR, "SELECT COUNT(*) FROM ( {$matches} ) AS tmdo_found" );
 		return $request;
 	}
 
+	/**
+	 * Keep WordPress's split query (IDs first, then cached post objects) on a
+	 * routed search: posts_request only dropped SQL_CALC_FOUND_ROWS, yet
+	 * WordPress takes any change for a filtered request and selects full rows
+	 * (a temporary table sorting whole posts). The split ID request passes
+	 * through posts_request_ids, which drops SQL_CALC_FOUND_ROWS again.
+	 *
+	 * @param bool                  $split       Core decision.
+	 * @param \WP_Query             $query       Current WP_Query.
+	 * @param string                $old_request Request before posts_request.
+	 * @param array<string, string> $clauses     Query clauses (fields, limits …).
+	 * @return bool
+	 */
+	public function split_the_query( $split, \WP_Query $query, $old_request = '', $clauses = array() ): bool {
+		$routed = ! empty( $query->get( self::QUERY_VAR ) ) || ! empty( $query->get( self::SORT_VAR ) );
+		if ( $split || ! $routed ) {
+			return (bool) $split;
+		}
+		global $wpdb;
+		// Core's other conditions: full rows, and a LIMIT under 500 or an external object cache.
+		return "{$wpdb->posts}.*" === ( $clauses['fields'] ?? '' )
+			&& self::without_found_rows( (string) $old_request ) === $query->request
+			&& ( ( '' !== ( $clauses['limits'] ?? '' ) && (int) $query->get( 'posts_per_page' ) < 500 ) || wp_using_ext_object_cache() );
+	}
+
 	/**
 	 * Answer found rows from the cached COUNT of a routed search.
 	 *
@@ -542,6 +569,16 @@ class TMDO_Post_Query_Router {
 		);
 	}
 
+	/**
+	 * A request without its SQL_CALC_FOUND_ROWS.
+	 *
+	 * @param string $request SELECT statement.
+	 * @return string
+	 */
+	private static function without_found_rows( string $request ): string {
+		return (string) preg_replace( '/\bSQL_CALC_FOUND_ROWS\s+/', '', $request, 1 );
+	}
+
 	/**
 	 * Whether a meta query type casts to a number (NUMERIC, SIGNED, DECIMAL(p,s) …).
 	 *

tests/integration/PostQueryRouterFoundRowsTest.php

@@ -133,4 +133,49 @@ class PostQueryRouterFoundRowsTest extends TestCase {
 		$this->assertNotSame( $before, $after_write );
 		$this->assertNotSame( $after_write, wp_cache_get_last_changed( 'posts' ) );
 	}
+
+	// ── split query: IDs first, then cached post objects ──────────────────
+
+	/**
+	 * WordPress's full-row request for a routed query, before and after posts_request.
+	 *
+	 * @return array{0:TMDO_Post_Query_Router, 1:WP_Query, 2:string, 3:array<string, string>}
+	 */
+	private function full_rows(): array {
+		global $wpdb;
+		list( $router, $query, $request ) = $this->routed();
+		$old_request    = str_replace( "{$wpdb->posts}.ID FROM", "{$wpdb->posts}.* FROM", $request );
+		$query->request = $router->posts_request( $old_request, $query );
+		$query->set( 'posts_per_page', 1 );
+		return array( $router, $query, $old_request, array( 'fields' => "{$wpdb->posts}.*", 'limits' => 'LIMIT 0, 1' ) );
+	}
+
+	public function test_routed_full_row_request_is_still_split(): void {
+		list( $router, $query, $old_request, $clauses ) = $this->full_rows();
+
+		$this->assertTrue( $router->split_the_query( false, $query, $old_request, $clauses ) );
+	}
+
+	public function test_request_changed_by_others_is_not_split(): void {
+		list( $router, $query, $old_request, $clauses ) = $this->full_rows();
+		$query->request .= ' /* another plugin */';
+
+		$this->assertFalse( $router->split_the_query( false, $query, $old_request, $clauses ) );
+	}
+
+	public function test_unrouted_query_keeps_the_core_decision(): void {
+		$router = new TMDO_Post_Query_Router();
+
+		$this->assertFalse( $router->split_the_query( false, new WP_Query(), 'SELECT 1', array( 'fields' => 'wp_itest_posts.*', 'limits' => 'LIMIT 0, 1' ) ) );
+		$this->assertTrue( $router->split_the_query( true, new WP_Query(), 'SELECT 1', array() ) );
+	}
+
+	public function test_split_id_request_goes_through_posts_request_too(): void {
+		unset( $GLOBALS['_wp_filter_callbacks']['posts_request_ids'], $GLOBALS['_wp_filter_callbacks']['split_the_query'] );
+		$router = new TMDO_Post_Query_Router();
+		$router->register_hooks();
+
+		$this->assertContains( array( $router, 'posts_request' ), $GLOBALS['_wp_filter_callbacks']['posts_request_ids'] ?? array() );
+		$this->assertContains( array( $router, 'split_the_query' ), $GLOBALS['_wp_filter_callbacks']['split_the_query'] ?? array() );
+	}
 }

tests/integration/bootstrap.php

@@ -418,6 +418,7 @@ if ( ! function_exists( 'wp_cache_delete' ) ) { function wp_cache_delete( $key,
 
 if ( ! class_exists( 'WP_Query' ) ) {
 	class WP_Query {
+		public string $request = '';
 		private array $vars = [];
 		public function get( string $key, $default = '' ) { return $this->vars[ $key ] ?? $default; }
 		public function set( string $key, $value ): void { $this->vars[ $key ] = $value; }

tests/live/suites/router.php

@@ -48,12 +48,7 @@ function tmdo_live_router_query( array $args, array $ids, bool $routed ): array
 			)
 		);
 	} finally {
-		foreach ( array( 'pre_get_posts', 'posts_join', 'posts_where', 'posts_orderby', 'posts_request', 'found_posts_query' ) as $hook ) {
+		tmdo_live_router_unhook( $router );
-			$priority = has_filter( $hook, array( $router, $hook ) );
-			if ( false !== $priority ) {
-				remove_filter( $hook, array( $router, $hook ), $priority );
-			}
-		}
 	}
 	tmdo_live_assert_same( '', $wpdb->last_error, 'SQL error' );
 	return array(
@@ -63,6 +58,22 @@ function tmdo_live_router_query( array $args, array $ids, bool $routed ): array
 	);
 }
 
+/**
+ * Remove every hook TMDO_Post_Query_Router::register_hooks() added.
+ *
+ * @param TMDO_Post_Query_Router $router Router instance.
+ */
+function tmdo_live_router_unhook( TMDO_Post_Query_Router $router ): void {
+	foreach ( array( 'pre_get_posts', 'posts_join', 'posts_where', 'posts_orderby', 'posts_request', 'split_the_query', 'found_posts_query' ) as $method ) {
+		foreach ( 'posts_request' === $method ? array( 'posts_request', 'posts_request_ids' ) : array( $method ) as $hook ) {
+			$priority = has_filter( $hook, array( $router, $method ) );
+			if ( false !== $priority ) {
+				remove_filter( $hook, array( $router, $method ), $priority );
+			}
+		}
+	}
+}
+
 /**
  * Create posts of $post_type with the given meta, in post mode shadow_read
  * (so the Hook Bus keeps the flat rows in step).
@@ -340,3 +351,33 @@ TMDO_Live::test(
 		);
 	}
 );
+
+TMDO_Live::test(
+	'a routed full-row search keeps the split query (IDs first) and native found_posts',
+	static function () {
+		global $wpdb;
+		$l    = tmdo_live_router_listings();
+		$args = array(
+			'post_type'      => 'hp_listing',
+			'post__in'       => array_values( $l ),
+			'post_status'    => 'any',
+			'posts_per_page' => 2,
+			'orderby'        => 'ID',
+			'order'          => 'ASC',
+			'meta_query'     => array( array( 'key' => 'hp_price', 'value' => 1000, 'compare' => '>=', 'type' => 'NUMERIC' ) ),
+		);
+		$native = new WP_Query( $args );
+		$router = new TMDO_Post_Query_Router();
+		$router->register_hooks();
+		try {
+			$routed = new WP_Query( $args );
+		} finally {
+			tmdo_live_router_unhook( $router );
+		}
+
+		tmdo_live_assert_same( wp_list_pluck( $native->posts, 'ID' ), wp_list_pluck( $routed->posts, 'ID' ), 'page of posts' );
+		tmdo_live_assert_same( $native->found_posts, $routed->found_posts, 'found_posts' );
+		tmdo_live_assert_true( false !== strpos( $routed->request, 'wpdoflat_' ), 'routed: ' . $routed->request );
+		tmdo_live_assert_true( 1 === preg_match( '/^\s*SELECT\s+' . preg_quote( $wpdb->posts, '/' ) . '\.ID\s/', $routed->request ), 'IDs first: ' . $routed->request );
+	}
+);