MySQL 8.0: Retiring Support for the Query Cache

Product Manager for the MySQL Server here (and post author). Happy to answer any questions...

These days it is much easier to implement a query cache specific to your application's needs in other layers of your infrastructure. These other layers also tend to scale horizontally much more easily than a relational database does. I like it.

It&#x27;s good that MySQL gets better because I&#x27;m tied to it since Sequel Pro is the best database browser there is and it only supports MySQL.<p>Datagrip has that Java kind of non-nativeness (weird scrolling and the looks) and it&#x27;s never easy to read&#x2F;write triggers, relations and export data into csv etc.<p>I did find Postico being decent last time I checked but what a limiting factor on the tooling.

&gt;&gt;Use of non-deterministic features will result in the query not being cached (including temporary tables, user variables, RAND(), NOW() and UDFs.)<p>Makes me wonder how many simplistic client side caches check for this. Pretty sure I&#x27;ve seen PHP shopping apps that blindly hash the query.

This PostgreSQL diehard had a usecase that required a cluster of 3 masters to stay up if two of them died. Turned out that was really easy with MySQL multi-master and multi-source where each master is a slave to the other two.

Though this is probably a good move, I think it&#x27;s going to catch out a lot of bad web apps based on my experience of trying to disable it at a web hosting company :-)

I always assumed that it makes sense to have the query cache active. It just makes sense logically.<p>On my production server, &quot;SHOW STATUS LIKE &#x27;Qcache%&#x27;&quot; currently gives me:<p><pre><code> Qcache_free_blocks 2184 Qcache_free_memory 7629288 Qcache_hits 328939349 Qcache_inserts 14440714 Qcache_lowmem_prunes 7814306 Qcache_not_cached 290027559 Qcache_queries_in_cache 7497 Qcache_total_blocks 17225 </code></pre> About 20 hits per insert. Sounds good to me.<p>Anybody here who is more &quot;in the know&quot; then me and can tell me what I can conclude from these numbers and&#x2F;or which other stats to look at?

It is definitely high time, the QC is an abomination, it&#x27;s totally at odds with the idea of MVCC.<p>In my experience, anyone who enabled the QC was deeply mistaken about its behaviour.

when optimizing old school server rendered web apps turning on the query cache always gave the most bang for the buck. hit rates around 90% or more.

Out of curiosity: how does people using Wordpress [at somewhat scale] handle layers of cache? Last I used it, relying on the Wordpress cache layer just didn&#x27;t cover enough cases. The MySQL one &quot;saved&quot; me seeing how Wordpress likes to ask the same question. A lot.

I am trying <a href="http:&#x2F;&#x2F;www.heimdalldata.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.heimdalldata.com&#x2F;</a> as a replacement.

I&#x27;m not sure that it will &quot;only affect a small number of users&quot;.<p>Maybe this should be an option with false as default value, it could help with the transition.

I&#x27;m working with a company called <a href="http:&#x2F;&#x2F;www.heimdalldata.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.heimdalldata.com&#x2F;</a> they do SQL auto-caching with no code changes. A perfect replacement for Query Cache if you have a read-heavy application. They also offer a nice dashboard that helps identify database inefficiencies. I would try them out to see if you get a performance boost.