Hi, Well let me just hawk into this discussion since we are running a query cache solution for the last two month based on:
## Storage engine We do not use any database table but instead rely on an available caching engine either APC, memcached or MW's own object cache. ## Query uniqueness Before a getQueryResult() is executed a hash key is generated from $query->getQueryString() . '#'. $query->getLimit() . '#' . $query->getOffset() . '#'. serialize( $printouts ) . '#' . serialize( $query->sortkeys ) which gives enough depth to ensure comparability among queries. ## Associated objects While having $res->getResults stored as single cache object (which is the simplest of all operations) the more important role goes to associated objects. Associated objects are individual entities (page, property etc.) that part of the result set and the condition and each stored as separated cache object (each associated object uses its own md5 hash key, easy to track any object with the same key during any update process). This allows to build a chain between objects and the query that requested its involvement. During each update process (onChangeTitle, onUpdateDataBefore, onDelete etc) an object and its hash key (it is a cheap operation due to its 1:1 relation) is checked against the cache pool and if an cache object exists the stored array of hash keys will point to all involved queries of that object. When one of these objects are detected during the update process they will be purged from cache ($cache->delete( $row ). If a change happened, a result is build up from scratch because of any potential alteration (we do not compare any change we assume a change happened and therefore the risk of an invalid result is higher than just having a new result set) that could have happened with one of the involved objects that caused the invalidation. Since we only use in-memory cache objects, we don't have to care about synchronization of table objects and we simply use the hash key as comparator, invalidator and chaining object. ## Result The greatest benefit will emerge from query results that only change occasionally and for queries with have a high turnover due to a high velocity on associated objects there has been no measurable downside (we use APC or memcached rather than a database). Cheers, mwjames ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Semediawiki-devel mailing list Semediawiki-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/semediawiki-devel
