Options/Meta APIs: Optimize cache hits for non-existent options.

Optimize the order of checking the various options caches in `get_option()` to prevent hitting external caches each time it is called for a known non-existent option.

The caches are checked in the following order when getting an option:

1. Check the `alloptions` cache first to prioritize existing loaded options.
2. Check the `notoptions` cache before a cache lookup or DB hit.
3. Check the `options` cache prior to a DB hit.

Follow up to [56595].

Props adamsilverstein, flixos90, ivankristianto, joemcgill, rmccue, siliconforks, spacedmonkey.
Fixes #62692.
See #58277.


git-svn-id: https://develop.svn.wordpress.org/trunk@59631 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/option.php

@@ -162,21 +162,26 @@ function get_option( $option, $default_value = false ) {
 
 	if ( ! wp_installing() ) {
 		$alloptions = wp_load_alloptions();
-
+		/*
+		 * When getting an option value, we check in the following order for performance:
+		 *
+		 * 1. Check the 'alloptions' cache first to prioritize existing loaded options.
+		 * 2. Check the 'notoptions' cache before a cache lookup or DB hit.
+		 * 3. Check the 'options' cache prior to a DB hit.
+		 * 4. Check the DB for the option and cache it in either the 'options' or 'notoptions' cache.
+		 */
 		if ( isset( $alloptions[ $option ] ) ) {
 			$value = $alloptions[ $option ];
 		} else {
-			$value = wp_cache_get( $option, 'options' );
-
-			if ( false === $value ) {
-				// Prevent non-existent options from triggering multiple queries.
+			// Check for non-existent options first to avoid unnecessary object cache lookups and DB hits.
 			$notoptions = wp_cache_get( 'notoptions', 'options' );
 
-				// Prevent non-existent `notoptions` key from triggering multiple key lookups.
 			if ( ! is_array( $notoptions ) ) {
 				$notoptions = array();
 				wp_cache_set( 'notoptions', $notoptions, 'options' );
-				} elseif ( isset( $notoptions[ $option ] ) ) {
+			}
+
+			if ( isset( $notoptions[ $option ] ) ) {
 				/**
 				 * Filters the default value for an option.
 				 *
@@ -194,6 +199,10 @@ function get_option( $option, $default_value = false ) {
 				return apply_filters( "default_option_{$option}", $default_value, $option, $passed_default );
 			}
 
+			$value = wp_cache_get( $option, 'options' );
+
+			if ( false === $value ) {
+
 				$row = $wpdb->get_row( $wpdb->prepare( "SELECT option_value FROM $wpdb->options WHERE option_name = %s LIMIT 1", $option ) );
 
 				// Has to be get_row() instead of get_var() because of funkiness with 0, false, null values.

tests/phpunit/tests/option/option.php

@@ -112,7 +112,7 @@ class Tests_Option_Option extends WP_UnitTestCase {
 		wp_cache_set( 'notoptions', $notoptions, 'options' );
 
 		$before = get_num_queries();
-		$value  = get_option( 'invalid' );
+		get_option( 'invalid' );
 		$after = get_num_queries();
 
 		$this->assertSame( 0, $after - $before );
@@ -127,7 +127,7 @@ class Tests_Option_Option extends WP_UnitTestCase {
 		get_option( 'invalid' );
 
 		$before = get_num_queries();
-		$value  = get_option( 'invalid' );
+		get_option( 'invalid' );
 		$after = get_num_queries();
 
 		$notoptions = wp_cache_get( 'notoptions', 'options' );
@@ -137,25 +137,6 @@ class Tests_Option_Option extends WP_UnitTestCase {
 		$this->assertArrayHasKey( 'invalid', $notoptions, 'The "invalid" option should be in the notoptions cache.' );
 	}
 
-	/**
-	 * @ticket 58277
-	 *
-	 * @covers ::get_option
-	 */
-	public function test_get_option_notoptions_do_not_load_cache() {
-		add_option( 'foo', 'bar', '', false );
-		wp_cache_delete( 'notoptions', 'options' );
-
-		$before = get_num_queries();
-		$value  = get_option( 'foo' );
-		$after  = get_num_queries();
-
-		$notoptions = wp_cache_get( 'notoptions', 'options' );
-
-		$this->assertSame( 0, $after - $before, 'The options cache was not hit on the second call to `get_option()`.' );
-		$this->assertFalse( $notoptions, 'The notoptions cache should not be set.' );
-	}
-
 	/**
 	 * @covers ::get_option
 	 * @covers ::add_option
@@ -548,4 +529,88 @@ class Tests_Option_Option extends WP_UnitTestCase {
 		$updated_notoptions = wp_cache_get( 'notoptions', 'options' );
 		$this->assertArrayNotHasKey( $option_name, $updated_notoptions, 'The "foobar" option should not be in the notoptions cache after adding it.' );
 	}
+
+	/**
+	 * Test that get_option() does not hit the external cache multiple times for the same option.
+	 *
+	 * @ticket 62692
+	 *
+	 * @covers ::get_option
+	 *
+	 * @dataProvider data_get_option_does_not_hit_the_external_cache_multiple_times_for_the_same_option
+	 *
+	 * @param int    $expected_connections Expected number of connections to the memcached server.
+	 * @param bool   $option_exists        Whether the option should be set. Default true.
+	 * @param string $autoload             Whether the option should be auto loaded. Default true.
+	 */
+	public function test_get_option_does_not_hit_the_external_cache_multiple_times_for_the_same_option( $expected_connections, $option_exists = true, $autoload = true ) {
+		if ( ! wp_using_ext_object_cache() ) {
+			$this->markTestSkipped( 'This test requires an external object cache.' );
+		}
+
+		if ( false === $this->helper_object_cache_stats_cmd_get() ) {
+			$this->markTestSkipped( 'This test requires access to the number of get requests to the external object cache.' );
+		}
+
+		if ( $option_exists ) {
+			add_option( 'ticket-62692', 'value', '', $autoload );
+		}
+
+		wp_cache_delete_multiple( array( 'ticket-62692', 'notoptions', 'alloptions' ), 'options' );
+
+		$connections_start = $this->helper_object_cache_stats_cmd_get();
+
+		$call_getter = 10;
+		while ( $call_getter-- ) {
+			get_option( 'ticket-62692' );
+		}
+
+		$connections_end = $this->helper_object_cache_stats_cmd_get();
+
+		$this->assertSame( $expected_connections, $connections_end - $connections_start );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_get_option_does_not_hit_the_external_cache_multiple_times_for_the_same_option() {
+		return array(
+			'exists, autoload'       => array( 1, true, true ),
+			'exists, not autoloaded' => array( 3, true, false ),
+			'does not exist'         => array( 3, false ),
+		);
+	}
+
+	/**
+	 * Helper function to get the number of get commands from the external object cache.
+	 *
+	 * @return int|false Number of get command calls, false if unavailable.
+	 */
+	public function helper_object_cache_stats_cmd_get() {
+		if ( ! wp_using_ext_object_cache() || ! function_exists( 'wp_cache_get_stats' ) ) {
+			return false;
+		}
+
+		$stats = wp_cache_get_stats();
+
+		// Check the shape of the stats.
+		if ( ! is_array( $stats ) ) {
+			return false;
+		}
+
+		// Get the first server's stats.
+		$stats = array_shift( $stats );
+
+		if ( ! is_array( $stats ) ) {
+			return false;
+		}
+
+		if ( ! array_key_exists( 'cmd_get', $stats ) ) {
+			return false;
+		}
+
+		return $stats['cmd_get'];
+	}
 }