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* @package WPSEO\XML_Sitemaps
* Handles storage keys for sitemaps caching and invalidation.
class WPSEO_Sitemaps_Cache_Validator {
* Prefix of the transient key for sitemap caches.
public const STORAGE_KEY_PREFIX = 'yst_sm_';
* Name of the option that holds the global validation value.
public const VALIDATION_GLOBAL_KEY = 'wpseo_sitemap_cache_validator_global';
* The format which creates the key of the option that holds the type validation value.
public const VALIDATION_TYPE_KEY_FORMAT = 'wpseo_sitemap_%s_cache_validator';
* Get the cache key for a certain type and page.
* A type of cache would be something like 'page', 'post' or 'video'.
* Example key format for sitemap type "post", page 1: wpseo_sitemap_post_1:akfw3e_23azBa .
* @param string|null $type The type to get the key for. Null or self::SITEMAP_INDEX_TYPE for index cache.
* @param int $page The page of cache to get the key for.
* @return bool|string The key where the cache is stored on. False if the key could not be generated.
public static function get_storage_key( $type = null, $page = 1 ) {
// Using SITEMAP_INDEX_TYPE for sitemap index cache.
$type = is_null( $type ) ? WPSEO_Sitemaps::SITEMAP_INDEX_TYPE : $type;
$global_cache_validator = self::get_validator();
$type_cache_validator = self::get_validator( $type );
$prefix = self::STORAGE_KEY_PREFIX;
$postfix = sprintf( '_%d:%s_%s', $page, $global_cache_validator, $type_cache_validator );
$type = self::truncate_type( $type, $prefix, $postfix );
} catch ( OutOfBoundsException $exception ) {
// Maybe do something with the exception, for now just mark as invalid.
$full_key = $prefix . $type . $postfix;
* If the type is over length make sure we compact it so we don't have any database problems.
* When there are more 'extremely long' post types, changes are they have variations in either the start or ending.
* Because of this, we cut out the excess in the middle which should result in less chance of collision.
* @param string $type The type of sitemap to be used.
* @param string $prefix The part before the type in the cache key. Only the length is used.
* @param string $postfix The part after the type in the cache key. Only the length is used.
* @return string The type with a safe length to use
* @throws OutOfRangeException When there is less than 15 characters of space for a key that is originally longer.
public static function truncate_type( $type, $prefix = '', $postfix = '' ) {
* This length has been restricted by the database column length of 64 in the past.
* The prefix added by WordPress is '_transient_' because we are saving to a transient.
* We need to use a timeout on the transient, otherwise the values get autoloaded, this adds
* another restriction to the length.
$max_length = 45; // 64 - 19 ('_transient_timeout_')
$max_length -= strlen( $prefix );
$max_length -= strlen( $postfix );
if ( strlen( $type ) > $max_length ) {
if ( $max_length < 15 ) {
* If this happens the most likely cause is a page number that is too high.
* So this would not happen unintentionally.
* Either by trying to cause a high server load, finding backdoors or misconfiguration.
throw new OutOfRangeException(
'Trying to build the sitemap cache key, but the postfix and prefix combination leaves too little room to do this. You are probably requesting a page that is way out of the expected range.',
$half = ( $max_length / 2 );
$first_part = substr( $type, 0, ( ceil( $half ) - 1 ) );
$last_part = substr( $type, ( 1 - floor( $half ) ) );
$type = $first_part . '..' . $last_part;
* Invalidate sitemap cache.
* @param string|null $type The type to get the key for. Null for all caches.
public static function invalidate_storage( $type = null ) {
// Global validator gets cleared when no type is provided.
// Get the current type validator.
if ( ! is_null( $type ) ) {
$old_validator = self::get_validator( $type );
self::create_validator( $type );
if ( ! wp_using_ext_object_cache() ) {
// Clean up current cache from the database.
self::cleanup_database( $type, $old_validator );
// External object cache pushes old and unretrieved items out by itself so we don't have to do anything for that.
* Cleanup invalidated database cache.
* @param string|null $type The type of sitemap to clear cache for.
* @param string|null $validator The validator to clear cache of.
public static function cleanup_database( $type = null, $validator = null ) {
if ( is_null( $type ) ) {
// Clear all cache if no type is provided.
$like = sprintf( '%s%%', self::STORAGE_KEY_PREFIX );
// Clear type cache for all type keys.
$like = sprintf( '%1$s%2$s_%%', self::STORAGE_KEY_PREFIX, $type );
* Add slashes to the LIKE "_" single character wildcard.
* We can't use `esc_like` here because we need the % in the query.
$where[] = sprintf( "option_name LIKE '%s'", addcslashes( '_transient_' . $like, '_' ) );
$where[] = sprintf( "option_name LIKE '%s'", addcslashes( '_transient_timeout_' . $like, '_' ) );
//phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- We need to use a direct query here.
//phpcs:disable WordPress.DB.DirectDatabaseQuery.NoCaching -- Reason: No relevant caches.
//phpcs:disable WordPress.DB.PreparedSQLPlaceholders -- %i placeholder is still not recognized.
'DELETE FROM %i WHERE ' . implode( ' OR ', array_fill( 0, count( $where ), '%s' ) ),
array_merge( [ $wpdb->options ], $where )
wp_cache_delete( 'alloptions', 'options' );
* Get the current cache validator.
* Without the type the global validator is returned.
* This can invalidate -all- keys in cache at once.
* With the type parameter the validator for that specific type can be invalidated.
* @param string $type Provide a type for a specific type validator, empty for global validator.
* @return string|null The validator for the supplied type.
public static function get_validator( $type = '' ) {
$key = self::get_validator_key( $type );
$current = get_option( $key, null );
if ( ! is_null( $current ) ) {
if ( self::create_validator( $type ) ) {
return self::get_validator( $type );
* Get the cache validator option key for the specified type.
* @param string $type Provide a type for a specific type validator, empty for global validator.
* @return string Validator to be used to generate the cache key.
public static function get_validator_key( $type = '' ) {
return self::VALIDATION_GLOBAL_KEY;
return sprintf( self::VALIDATION_TYPE_KEY_FORMAT, $type );
* Refresh the cache validator value.
* @param string $type Provide a type for a specific type validator, empty for global validator.
* @return bool True if validator key has been saved as option.
public static function create_validator( $type = '' ) {
$key = self::get_validator_key( $type );
// Generate new validator.
$microtime = microtime();
list( $milliseconds, $seconds ) = explode( ' ', $microtime );
// Transients are purged every 24h.
$seconds = ( $seconds % DAY_IN_SECONDS );
$milliseconds = intval( substr( $milliseconds, 2, 3 ), 10 );
// Combine seconds and milliseconds and convert to integer.
$validator = intval( $seconds . '' . $milliseconds, 10 );
// Apply base 61 encoding.
$compressed = self::convert_base10_to_base61( $validator );
return update_option( $key, $compressed, false );
* Encode to base61 format.
* This is base64 (numeric + alpha + alpha upper case) without the 0.
* @param int $base10 The number that has to be converted to base 61.
* @return string Base 61 converted string.
* @throws InvalidArgumentException When the input is not an integer.
public static function convert_base10_to_base61( $base10 ) {
if ( ! is_int( $base10 ) ) {
throw new InvalidArgumentException( __( 'Expected an integer as input.', 'wordpress-seo' ) );
// Characters that will be used in the conversion.
$characters = '123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$length = strlen( $characters );
// Building from right to left in the result.
$index = ( $remainder % $length );
// Prepend the character to the output.
$output = $characters[ $index ] . $output;
// Determine the remainder after removing the applied number.
$remainder = floor( $remainder / $length );
// Keep doing it until we have no remainder left.
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
