diff options
Diffstat (limited to 'engine/classes/ElggVolatileMetadataCache.php')
| -rw-r--r-- | engine/classes/ElggVolatileMetadataCache.php | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/engine/classes/ElggVolatileMetadataCache.php b/engine/classes/ElggVolatileMetadataCache.php new file mode 100644 index 000000000..4acda7cee --- /dev/null +++ b/engine/classes/ElggVolatileMetadataCache.php @@ -0,0 +1,355 @@ +<?php +/** + * ElggVolatileMetadataCache + * In memory cache of known metadata values stored by entity. + * + * @package Elgg.Core + * @subpackage Cache + * + * @access private + */ +class ElggVolatileMetadataCache { + + /** + * The cached values (or null for known to be empty). If the portion of the cache + * is synchronized, missing values are assumed to indicate that values do not + * exist in storage, otherwise, we don't know what's there. + * + * @var array + */ + protected $values = array(); + + /** + * Does the cache know that it contains all names fetch-able from storage? + * The keys are entity GUIDs and either the value exists (true) or it's not set. + * + * @var array + */ + protected $isSynchronized = array(); + + /** + * @var null|bool + */ + protected $ignoreAccess = null; + + /** + * Cache metadata for an entity + * + * @param int $entity_guid The GUID of the entity + * @param array $values The metadata values to cache + * @return void + */ + public function saveAll($entity_guid, array $values) { + if (!$this->getIgnoreAccess()) { + $this->values[$entity_guid] = $values; + $this->isSynchronized[$entity_guid] = true; + } + } + + /** + * Get the metadata for an entity + * + * @param int $entity_guid The GUID of the entity + * @return array + */ + public function loadAll($entity_guid) { + if (isset($this->values[$entity_guid])) { + return $this->values[$entity_guid]; + } else { + return array(); + } + } + + /** + * Declare that there may be fetch-able metadata names in storage that this + * cache doesn't know about + * + * @param int $entity_guid The GUID of the entity + * @return void + */ + public function markOutOfSync($entity_guid) { + unset($this->isSynchronized[$entity_guid]); + } + + /** + * Have all the metadata for this entity been cached? + * + * @param int $entity_guid The GUID of the entity + * @return bool + */ + public function isSynchronized($entity_guid) { + return isset($this->isSynchronized[$entity_guid]); + } + + /** + * Cache a piece of metadata + * + * @param int $entity_guid The GUID of the entity + * @param string $name The metadata name + * @param array|int|string|null $value The metadata value. null means it is + * known that there is no fetch-able + * metadata under this name + * @param bool $allow_multiple Can the metadata be an array + * @return void + */ + public function save($entity_guid, $name, $value, $allow_multiple = false) { + if ($this->getIgnoreAccess()) { + // we don't know if what gets saves here will be available to user once + // access control returns, hence it's best to forget :/ + $this->markUnknown($entity_guid, $name); + } else { + if ($allow_multiple) { + if ($this->isKnown($entity_guid, $name)) { + $existing = $this->load($entity_guid, $name); + if ($existing !== null) { + $existing = (array) $existing; + $existing[] = $value; + $value = $existing; + } + } else { + // we don't know whether there are unknown values, so it's + // safest to leave that assumption + $this->markUnknown($entity_guid, $name); + return; + } + } + $this->values[$entity_guid][$name] = $value; + } + } + + /** + * Warning: You should always call isKnown() beforehand to verify that this + * function's return value should be trusted (otherwise a null return value + * is ambiguous). + * + * @param int $entity_guid The GUID of the entity + * @param string $name The metadata name + * @return array|string|int|null null = value does not exist + */ + public function load($entity_guid, $name) { + if (isset($this->values[$entity_guid]) && array_key_exists($name, $this->values[$entity_guid])) { + return $this->values[$entity_guid][$name]; + } else { + return null; + } + } + + /** + * Forget about this metadata entry. We don't want to try to guess what the + * next fetch from storage will return + * + * @param int $entity_guid The GUID of the entity + * @param string $name The metadata name + * @return void + */ + public function markUnknown($entity_guid, $name) { + unset($this->values[$entity_guid][$name]); + $this->markOutOfSync($entity_guid); + } + + /** + * If true, load() will return an accurate value for this name + * + * @param int $entity_guid The GUID of the entity + * @param string $name The metadata name + * @return bool + */ + public function isKnown($entity_guid, $name) { + if (isset($this->isSynchronized[$entity_guid])) { + return true; + } else { + return (isset($this->values[$entity_guid]) && array_key_exists($name, $this->values[$entity_guid])); + } + + } + + /** + * Declare that metadata under this name is known to be not fetch-able from storage + * + * @param int $entity_guid The GUID of the entity + * @param string $name The metadata name + * @return array + */ + public function markEmpty($entity_guid, $name) { + $this->values[$entity_guid][$name] = null; + } + + /** + * Forget about all metadata for an entity + * + * @param int $entity_guid The GUID of the entity + * @return void + */ + public function clear($entity_guid) { + $this->values[$entity_guid] = array(); + $this->markOutOfSync($entity_guid); + } + + /** + * Clear entire cache and mark all entities as out of sync + * + * @return void + */ + public function flush() { + $this->values = array(); + $this->isSynchronized = array(); + } + + /** + * Use this value instead of calling elgg_get_ignore_access(). By default that + * function will be called. + * + * This setting makes this component a little more loosely-coupled. + * + * @param bool $ignore Whether to ignore access or not + * @return void + */ + public function setIgnoreAccess($ignore) { + $this->ignoreAccess = (bool) $ignore; + } + + /** + * Tell the cache to call elgg_get_ignore_access() to determing access status. + * + * @return void + */ + public function unsetIgnoreAccess() { + $this->ignoreAccess = null; + } + + /** + * Get the ignore access value + * + * @return bool + */ + protected function getIgnoreAccess() { + if (null === $this->ignoreAccess) { + return elgg_get_ignore_access(); + } else { + return $this->ignoreAccess; + } + } + + /** + * Invalidate based on options passed to the global *_metadata functions + * + * @param string $action Action performed on metadata. "delete", "disable", or "enable" + * @param array $options Options passed to elgg_(delete|disable|enable)_metadata + * "guid" if given, invalidation will be limited to this entity + * "metadata_name" if given, invalidation will be limited to metadata with this name + * @return void + */ + public function invalidateByOptions($action, array $options) { + // remove as little as possible, optimizing for common cases + if (empty($options['guid'])) { + // safest to clear everything unless we want to make this even more complex :( + $this->flush(); + } else { + if (empty($options['metadata_name'])) { + // safest to clear the whole entity + $this->clear($options['guid']); + } else { + switch ($action) { + case 'delete': + $this->markEmpty($options['guid'], $options['metadata_name']); + break; + default: + $this->markUnknown($options['guid'], $options['metadata_name']); + } + } + } + } + + /** + * Populate the cache from a set of entities + * + * @param int|array $guids Array of or single GUIDs + * @return void + */ + public function populateFromEntities($guids) { + if (empty($guids)) { + return; + } + if (!is_array($guids)) { + $guids = array($guids); + } + $guids = array_unique($guids); + + // could be useful at some point in future + //$guids = $this->filterMetadataHeavyEntities($guids); + + $db_prefix = elgg_get_config('dbprefix'); + $options = array( + 'guids' => $guids, + 'limit' => 0, + 'callback' => false, + 'joins' => array( + "JOIN {$db_prefix}metastrings v ON n_table.value_id = v.id", + "JOIN {$db_prefix}metastrings n ON n_table.name_id = n.id", + ), + 'selects' => array('n.string AS name', 'v.string AS value'), + 'order_by' => 'n_table.entity_guid, n_table.time_created ASC', + + // @todo don't know why this is necessary + 'wheres' => array(get_access_sql_suffix('n_table')), + ); + $data = elgg_get_metadata($options); + + // build up metadata for each entity, save when GUID changes (or data ends) + $last_guid = null; + $metadata = array(); + $last_row_idx = count($data) - 1; + foreach ($data as $i => $row) { + $name = $row->name; + $value = ($row->value_type === 'text') ? $row->value : (int) $row->value; + $guid = $row->entity_guid; + if ($guid !== $last_guid) { + if ($last_guid) { + $this->saveAll($last_guid, $metadata); + } + $metadata = array(); + } + if (isset($metadata[$name])) { + $metadata[$name] = (array) $metadata[$name]; + $metadata[$name][] = $value; + } else { + $metadata[$name] = $value; + } + if (($i == $last_row_idx)) { + $this->saveAll($guid, $metadata); + } + $last_guid = $guid; + } + } + + /** + * Filter out entities whose concatenated metadata values (INTs casted as string) + * exceed a threshold in characters. This could be used to avoid overpopulating the + * cache if RAM usage becomes an issue. + * + * @param array $guids GUIDs of entities to examine + * @param int $limit Limit in characters of all metadata (with ints casted to strings) + * @return array + */ + public function filterMetadataHeavyEntities(array $guids, $limit = 1024000) { + $db_prefix = elgg_get_config('dbprefix'); + + $options = array( + 'guids' => $guids, + 'limit' => 0, + 'callback' => false, + 'joins' => "JOIN {$db_prefix}metastrings v ON n_table.value_id = v.id", + 'selects' => array('SUM(LENGTH(v.string)) AS bytes'), + 'order_by' => 'n_table.entity_guid, n_table.time_created ASC', + 'group_by' => 'n_table.entity_guid', + ); + $data = elgg_get_metadata($options); + // don't cache if metadata for entity is over 10MB (or rolled INT) + foreach ($data as $row) { + if ($row->bytes > $limit || $row->bytes < 0) { + array_splice($guids, array_search($row->entity_guid, $guids), 1); + } + } + return $guids; + } +} |