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. 

Built from https://develop.svn.wordpress.org/trunk@52921


git-svn-id: http://core.svn.wordpress.org/trunk@52510 1a063a9b-81f0-0310-95a4-ce76da25c4cd

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 ";
+	$defaults = array(
-	$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 ";
+		'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';
+		$args  = wp_parse_args( array( 'include' => array( $term ) ), $defaults );
-		if ( ! empty( $taxonomy ) ) {
+		$terms = get_terms( $args );
-			// phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber
+	} else {
-			return $wpdb->get_row( $wpdb->prepare( $tax_select . $where . ' AND tt.taxonomy = %s', $term, $taxonomy ), ARRAY_A );
+		$term = trim( wp_unslash( $term ) );
-		} else {
+		if ( '' === $term ) {
-			return $wpdb->get_var( $wpdb->prepare( $select . $where, $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 ) );
+	if ( empty( $terms ) || is_wp_error( $terms ) ) {
-	$slug = sanitize_title( $term );
+		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 ) ) {
+		return array(
-			$parent              = (int) $parent;
+			'term_id'          => (string) $_term->term_id,
-			$where_fields[]      = $parent;
+			'term_taxonomy_id' => (string) $_term->term_taxonomy_id,
-			$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 );
 	}
 
-	// phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare
+	return (string) $_term;
-	$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 ) );
 }
 
 /**

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.0-alpha-52895';
+$wp_version = '6.0-alpha-52921';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.