fix(2meet-data-optimizer): keep meta_key native when the query still orders by it

- meta_key is routed as EXISTS only when no orderby entry names meta_value,
  meta_value_num or the key (several orderings or an array included);
  clearing it made WordPress drop the price ordering
- A sort group is dropped as unused only when orderby names neither it,
  meta_value(_num) nor its key (it is then the primary clause)
- meta_compare_key other than '=' keeps meta_key native (LIKE matches other keys)
- Found in the 2.4 correctness review (regressions from PR-122)
- Verify: PostQueryRouterTest (3 new), router suites 67 OK
- PR: PR-130

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

@@ -172,8 +172,11 @@ class TMDO_Post_Query_Router {
 
 		// meta_key + orderby meta_value(_num): native INNER JOINs the key
 		// (EXISTS) and orders by meta_value+0 (NUMERIC) or meta_value.
-		$meta_key = $query->get( 'meta_key' );
-		$take_key = is_string( $meta_key ) && in_array( $sort_name, array( 'meta_value', 'meta_value_num' ), true )
+		// A key comparison other than equality (meta_compare_key LIKE …) matches
+		// other keys too: not a test on one flat column.
+		$meta_key  = $query->get( 'meta_key' );
+		$key_exact = in_array( (string) $query->get( 'meta_compare_key' ), array( '', '=' ), true );
+		$take_key  = $key_exact && is_string( $meta_key ) && in_array( $sort_name, array( 'meta_value', 'meta_value_num' ), true )
 			&& null !== self::field_for( array( 'key' => $meta_key ), $pt );
 		if ( $take_key ) {
 			$field = self::field_for( array( 'key' => $meta_key ), $pt );
@@ -192,11 +195,13 @@ class TMDO_Post_Query_Router {
 			$routed[ $pt ][] = $route;
 			$sort            = self::sort_for( $pt, $route, $direction );
 		}
-		// meta_key alone (no meta_value, not a meta_value sort): WP_Query adds a
-		// clause that tests the key exists — HivePress's featured-listing lookup.
-		$exists_key = ! $take_key && is_string( $meta_key ) && '' !== $meta_key
+		// meta_key alone (no meta_value, not ordered by): WP_Query adds a clause
+		// that tests the key exists — HivePress's featured-listing lookup. Any
+		// orderby naming meta_value, meta_value_num or the key sorts by that
+		// clause, which clearing meta_key would drop.
+		$exists_key = ! $take_key && $key_exact && is_string( $meta_key ) && '' !== $meta_key
 			&& '' === (string) $query->get( 'meta_value' ) && '' === (string) $query->get( 'meta_compare' )
-			&& ! in_array( $sort_name, array( 'meta_value', 'meta_value_num' ), true )
+			&& ! array_intersect( $named, array( 'meta_value', 'meta_value_num', $meta_key ) )
 			&& null !== self::field_for( array( 'key' => $meta_key ), $pt );
 		if ( $exists_key ) {
 			$route = self::route_clause(
@@ -220,8 +225,12 @@ class TMDO_Post_Query_Router {
 			if ( ! isset( $clause['key'] ) ) {
 				// Sort shape: matches every post, only orders by the key.
 				$name = 'AND' === $relation ? self::sort_shape( $clause ) : '';
-				if ( '' !== $name && ! in_array( $name, $named, true ) && self::field_for( $clause[ $name ], $pt ) ) {
-					continue; // Matches every post and orders nothing here (a copy of a search's meta query).
+				// Matches every post and orders nothing here (a copy of a search's meta
+				// query) — unless orderby names it, or meta_value(_num) / its key, which
+				// sort by it when it is WordPress's primary (first) clause.
+				if ( '' !== $name && ! array_intersect( $named, array( $name, 'meta_value', 'meta_value_num', (string) ( $clause[ $name ]['key'] ?? '' ) ) )
+					&& self::field_for( $clause[ $name ], $pt ) ) {
+					continue;
 				}
 				$field = '' !== $name && $name === $sort_name ? self::field_for( $clause[ $name ], $pt ) : null;
 				if ( $field ) {

tests/integration/PostQueryRouterTest.php

@@ -471,6 +471,61 @@ class PostQueryRouterTest extends TestCase {
 		$this->assertStringContainsString( 'BETWEEN', $where );
 	}
 
+	/**
+	 * WordPress orders by the primary meta clause (meta_key) for meta_value,
+	 * meta_value_num or the key's name anywhere in orderby; routing the key and
+	 * clearing meta_key would drop that ordering (2.4 correctness review).
+	 */
+	public function test_meta_key_ordered_by_among_several_orderings_stays_native(): void {
+		foreach ( array(
+			array( 'meta_value_num' => 'ASC', 'title' => 'ASC' ),
+			'meta_value date',
+			'_stock',
+		) as $orderby ) {
+			$this->set_post_mode( 'aeav_only' );
+			$query = $this->make_query( array( 'post_type' => 'product', 'meta_key' => '_stock', 'orderby' => $orderby ) );
+			( new WPDO_Post_Query_Router() )->pre_get_posts( $query );
+
+			$label = is_array( $orderby ) ? implode( ',', array_keys( $orderby ) ) : $orderby;
+			$this->assertSame( '_stock', $query->get( 'meta_key' ), $label );
+			$this->assertSame( '', $query->get( 'wpdo_post_clauses' ), $label );
+		}
+	}
+
+	/** meta_compare_key LIKE matches other keys too: not a test on one flat column. */
+	public function test_meta_key_with_a_key_comparison_stays_native(): void {
+		foreach ( array( 'rand', 'meta_value_num' ) as $orderby ) {
+			$this->set_post_mode( 'aeav_only' );
+			$query = $this->make_query( array( 'post_type' => 'product', 'meta_key' => '_stock', 'meta_compare_key' => 'LIKE', 'orderby' => $orderby ) );
+			( new WPDO_Post_Query_Router() )->pre_get_posts( $query );
+
+			$this->assertSame( '_stock', $query->get( 'meta_key' ), $orderby );
+			$this->assertSame( '', $query->get( 'wpdo_post_clauses' ), $orderby );
+		}
+	}
+
+	/**
+	 * Without meta_key the first clause is WordPress's primary one: orderby
+	 * meta_value_num sorts by the sort group's key, so the group stays.
+	 */
+	public function test_sort_group_ordered_as_the_primary_clause_is_not_dropped(): void {
+		$this->assert_not_routed(
+			array(
+				'post_type'  => 'product',
+				'orderby'    => 'meta_value_num',
+				'meta_query' => array(
+					array(
+						'relation'     => 'OR',
+						'price__order' => array( 'key' => '_price', 'compare' => 'NOT EXISTS', 'type' => 'DECIMAL' ),
+						array( 'key' => '_price', 'compare' => 'EXISTS', 'type' => 'DECIMAL' ),
+					),
+					array( 'key' => '_stock', 'value' => 1, 'compare' => '>=', 'type' => 'NUMERIC' ),
+				),
+			),
+			'primary sort group'
+		);
+	}
+
 	public function test_meta_key_with_a_value_is_left_alone(): void {
 		$this->set_post_mode( 'aeav_only' );
 		$router = new WPDO_Post_Query_Router();