Taxonomy: Use get_terms instead of a database lookup in term_exists().

Replace raw SQL queries to the terms table, with a call to the `get_terms` function. Using `get_terms` means that `term_exists` is now cached. For developers using `term_exists` where cache invalidation is disabled, such as importing, a workaround was added to ensure that queries are uncached. 

Props Spacedmonkey, boonebgorges, flixos90, peterwilsoncc. 
Fixes #36949. 


git-svn-id: https://develop.svn.wordpress.org/trunk@52921 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/taxonomy.php

@@ -1519,8 +1519,9 @@ function unregister_term_meta( $taxonomy, $meta_key ) {
  * Conditional Tags} article in the Theme Developer Handbook.
  *
  * @since 3.0.0
+ * @since 6.0.0 Converted to use `get_terms()`.
  *
- * @global wpdb $wpdb WordPress database abstraction object.
+ * @global bool $_wp_suspend_cache_invalidation
  *
  * @param int|string $term     The term to check. Accepts term ID, slug, or name.
  * @param string     $taxonomy Optional. The taxonomy name to use.
@@ -1531,65 +1532,71 @@ function unregister_term_meta( $taxonomy, $meta_key ) {
  *               Returns 0 if term ID 0 is passed to the function.
  */
 function term_exists( $term, $taxonomy = '', $parent = null ) {
-	global $wpdb;
+	global $_wp_suspend_cache_invalidation;
 
 	if ( null === $term ) {
 		return null;
 	}
 
-	$select     = "SELECT term_id FROM $wpdb->terms as t WHERE ";
-	$tax_select = "SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE ";
+	$defaults = array(
+		'get'                    => 'all',
+		'fields'                 => 'ids',
+		'number'                 => 1,
+		'update_term_meta_cache' => false,
+		'order'                  => 'ASC',
+		'orderby'                => 'term_id',
+		'suppress_filter'        => true,
+	);
+
+	// Ensure that while importing, queries are not cached.
+	if ( ! empty( $_wp_suspend_cache_invalidation ) ) {
+		// @todo Disable caching once #52710 is merged.
+		$defaults['cache_domain'] = microtime();
+	}
+
+	if ( ! empty( $taxonomy ) ) {
+		$defaults['taxonomy'] = $taxonomy;
+		$defaults['fields']   = 'all';
+	}
 
 	if ( is_int( $term ) ) {
 		if ( 0 === $term ) {
 			return 0;
 		}
-		$where = 't.term_id = %d';
-		if ( ! empty( $taxonomy ) ) {
-			// phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber
-			return $wpdb->get_row( $wpdb->prepare( $tax_select . $where . ' AND tt.taxonomy = %s', $term, $taxonomy ), ARRAY_A );
-		} else {
-			return $wpdb->get_var( $wpdb->prepare( $select . $where, $term ) );
+		$args  = wp_parse_args( array( 'include' => array( $term ) ), $defaults );
+		$terms = get_terms( $args );
+	} else {
+		$term = trim( wp_unslash( $term ) );
+		if ( '' === $term ) {
+			return null;
+		}
+
+		if ( ! empty( $taxonomy ) && is_numeric( $parent ) ) {
+			$defaults['parent'] = (int) $parent;
+		}
+
+		$args  = wp_parse_args( array( 'slug' => sanitize_title( $term ) ), $defaults );
+		$terms = get_terms( $args );
+		if ( empty( $terms ) || is_wp_error( $terms ) ) {
+			$args  = wp_parse_args( array( 'name' => $term ), $defaults );
+			$terms = get_terms( $args );
 		}
 	}
 
-	$term = trim( wp_unslash( $term ) );
-	$slug = sanitize_title( $term );
+	if ( empty( $terms ) || is_wp_error( $terms ) ) {
+		return null;
+	}
+
+	$_term = array_shift( $terms );
 
-	$where             = 't.slug = %s';
-	$else_where        = 't.name = %s';
-	$where_fields      = array( $slug );
-	$else_where_fields = array( $term );
-	$orderby           = 'ORDER BY t.term_id ASC';
-	$limit             = 'LIMIT 1';
 	if ( ! empty( $taxonomy ) ) {
-		if ( is_numeric( $parent ) ) {
-			$parent              = (int) $parent;
-			$where_fields[]      = $parent;
-			$else_where_fields[] = $parent;
-			$where              .= ' AND tt.parent = %d';
-			$else_where         .= ' AND tt.parent = %d';
-		}
-
-		$where_fields[]      = $taxonomy;
-		$else_where_fields[] = $taxonomy;
-
-		$result = $wpdb->get_row( $wpdb->prepare( "SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $where AND tt.taxonomy = %s $orderby $limit", $where_fields ), ARRAY_A );
-		if ( $result ) {
-			return $result;
-		}
-
-		return $wpdb->get_row( $wpdb->prepare( "SELECT tt.term_id, tt.term_taxonomy_id FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy as tt ON tt.term_id = t.term_id WHERE $else_where AND tt.taxonomy = %s $orderby $limit", $else_where_fields ), ARRAY_A );
+		return array(
+			'term_id'          => (string) $_term->term_id,
+			'term_taxonomy_id' => (string) $_term->term_taxonomy_id,
+		);
 	}
 
-	// phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare
-	$result = $wpdb->get_var( $wpdb->prepare( "SELECT term_id FROM $wpdb->terms as t WHERE $where $orderby $limit", $where_fields ) );
-	if ( $result ) {
-		return $result;
-	}
-
-	// phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare
-	return $wpdb->get_var( $wpdb->prepare( "SELECT term_id FROM $wpdb->terms as t WHERE $else_where $orderby $limit", $else_where_fields ) );
+	return (string) $_term;
 }
 
 /**

tests/phpunit/tests/term/getTerm.php

@@ -31,6 +31,8 @@ class Tests_Term_GetTerm extends WP_UnitTestCase {
 			array( '%d' )
 		);
 
+		clean_term_cache( $t1['term_id'] );
+
 		return array(
 			array(
 				'term_id'          => $t1['term_id'],

tests/phpunit/tests/term/splitSharedTerm.php

@@ -54,6 +54,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( '%d' ),
 			array( '%d' )
 		);
+		clean_term_cache( $t1['term_id'], 'category' );
 
 		$t2_child = wp_insert_term(
 			'Foo Child',
@@ -151,6 +152,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( '%d' ),
 			array( '%d' )
 		);
+		clean_term_cache( $t1['term_id'], 'category' );
 		$th = _get_term_hierarchy( 'wptests_tax_4' );
 
 		$new_term_id = _split_shared_term( $t1['term_id'], $t3['term_taxonomy_id'] );
@@ -179,6 +181,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( '%d' ),
 			array( '%d' )
 		);
+		clean_term_cache( $t1['term_id'], 'category' );
 
 		$this->assertSame( $t1['term_id'], get_option( 'default_category', -1 ) );
 
@@ -207,6 +210,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( '%d' ),
 			array( '%d' )
 		);
+		clean_term_cache( $t1['term_id'], 'category' );
 
 		$menu_id       = wp_create_nav_menu( 'Nav Menu Bar' );
 		$cat_menu_item = wp_update_nav_menu_item(
@@ -245,6 +249,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( 'term_id' => $shared_term_id ),
 			array( 'term_taxonomy_id' => $nav_term->term_taxonomy_id )
 		);
+		clean_term_cache( $shared_term_id, 'category' );
 
 		set_theme_mod( 'nav_menu_locations', array( 'foo' => $shared_term_id ) );
 
@@ -274,6 +279,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( 'term_id' => $shared_term_id ),
 			array( 'term_taxonomy_id' => $nav_term->term_taxonomy_id )
 		);
+		clean_term_cache( $shared_term_id, 'category' );
 
 		$t1            = wp_insert_term( 'Random term', 'category' );
 		$cat_menu_item = wp_update_nav_menu_item(

tests/phpunit/tests/term/termExists.php

@@ -271,6 +271,132 @@ class Tests_TermExists extends WP_UnitTestCase {
 		_unregister_taxonomy( 'wptests_tax' );
 	}
 
+	/**
+	 * @ticket 36949
+	 * @covers ::term_exists()
+	 */
+	public function test_term_lookup_by_id_and_update() {
+		register_taxonomy( 'wptests_tax', 'post' );
+
+		$slug = __FUNCTION__;
+		$t    = self::factory()->term->create(
+			array(
+				'slug'     => $slug,
+				'taxonomy' => 'wptests_tax',
+			)
+		);
+		$this->assertEquals( $t, term_exists( $t ) );
+		$this->assertTrue( wp_delete_term( $t, 'wptests_tax' ) );
+		$this->assertNull( term_exists( $t ) );
+
+		// Clean up.
+		_unregister_taxonomy( 'wptests_tax' );
+	}
+
+	/**
+	 * @ticket 36949
+	 * @covers ::term_exists()
+	 */
+	public function test_term_lookup_by_slug_and_update() {
+		register_taxonomy( 'wptests_tax', 'post' );
+
+		$slug = __FUNCTION__;
+		$t    = self::factory()->term->create(
+			array(
+				'slug'     => $slug,
+				'taxonomy' => 'wptests_tax',
+			)
+		);
+		$this->assertEquals( $t, term_exists( $slug ) );
+		$this->assertTrue( wp_delete_term( $t, 'wptests_tax' ) );
+		$this->assertNull( term_exists( $slug ) );
+
+		// Clean up.
+		_unregister_taxonomy( 'wptests_tax' );
+	}
+
+	/**
+	 * @ticket 36949
+	 * @covers ::term_exists()
+	 */
+	public function test_term_exists_caching() {
+		global $wpdb;
+		register_taxonomy( 'wptests_tax', 'post' );
+
+		$slug = __FUNCTION__;
+		$t    = self::factory()->term->create(
+			array(
+				'slug'     => $slug,
+				'taxonomy' => 'wptests_tax',
+			)
+		);
+		$this->assertEquals( $t, term_exists( $slug ) );
+		$num_queries = $wpdb->num_queries;
+		$this->assertEquals( $t, term_exists( $slug ) );
+		$this->assertSame( $num_queries, $wpdb->num_queries );
+
+		$this->assertTrue( wp_delete_term( $t, 'wptests_tax' ) );
+		$num_queries = $wpdb->num_queries;
+		$this->assertNull( term_exists( $slug ) );
+		$this->assertSame( $num_queries + 2, $wpdb->num_queries );
+
+		// Clean up.
+		_unregister_taxonomy( 'wptests_tax' );
+	}
+
+	/**
+	 * @ticket 36949
+	 * @covers ::term_exists()
+	 */
+	public function test_term_exists_caching_suspend_cache_invalidation() {
+		global $wpdb;
+		register_taxonomy( 'wptests_tax', 'post' );
+
+		wp_suspend_cache_invalidation( true );
+		$slug = __FUNCTION__;
+		$t    = self::factory()->term->create(
+			array(
+				'slug'     => $slug,
+				'taxonomy' => 'wptests_tax',
+			)
+		);
+
+		$this->assertEquals( $t, term_exists( $slug ) );
+		$num_queries = $wpdb->num_queries;
+		$this->assertEquals( $t, term_exists( $slug ) );
+		$this->assertSame( $num_queries + 1, $wpdb->num_queries );
+		wp_suspend_cache_invalidation( false );
+
+		// Clean up.
+		_unregister_taxonomy( 'wptests_tax' );
+	}
+
+	/**
+	 * @ticket 36949
+	 * @covers ::term_exists()
+	 */
+	public function test_term_exists_caching_by_int_suspend_cache_invalidation() {
+		register_taxonomy( 'wptests_tax', 'post' );
+
+		$slug = __FUNCTION__;
+		$t    = self::factory()->term->create(
+			array(
+				'slug'     => $slug,
+				'taxonomy' => 'wptests_tax',
+			)
+		);
+
+		// Warm cache in get_term() via term_exists().
+		term_exists( $t );
+		wp_suspend_cache_invalidation( true );
+		wp_delete_term( $t, 'wptests_tax' );
+		$this->assertNull( term_exists( $t ) );
+
+		// Reneable cache invalidation.
+		wp_suspend_cache_invalidation( false );
+		_unregister_taxonomy( 'wptests_tax' );
+	}
+
 	public function test_term_exists_unknown() {
 		$this->assertNull( term_exists( rand_str() ) );
 		$this->assertSame( 0, term_exists( 0 ) );

tests/phpunit/tests/term/wpGetObjectTerms.php

@@ -447,6 +447,8 @@ class Tests_Term_WpGetObjectTerms extends WP_UnitTestCase {
 		$wpdb->update( $wpdb->term_taxonomy, array( 'term_taxonomy_id' => 100006 ), array( 'term_taxonomy_id' => $term_2->term_taxonomy_id ) );
 		$wpdb->update( $wpdb->term_taxonomy, array( 'term_taxonomy_id' => 100005 ), array( 'term_taxonomy_id' => $term_3->term_taxonomy_id ) );
 
+		clean_term_cache( array( $t1, $t2, $t3 ), $this->taxonomy );
+
 		$set = wp_set_object_terms( $p, array( $t1, $t2, $t3 ), $this->taxonomy );
 
 		$found = wp_get_object_terms(