File based query cache

[thekonz]

• Added or updated tests
• Documented user facing changes
• Updated CHANGELOG.md

Changes

Just like the schema cache, now the query cache can be picked up by opcache.

Breaking changes

None expected.

[spawnia]

Hi @thekonz, thank you for contributing this feature. I am installing it in one of our projects right now for testing and will provide a thorough review together with some performance measurements soon.

[thekonz]

hi, thanks for reviewing! currently sick with covid. will get back to you later this week 😷

[spawnia]

I hope you get better soon, no rush on this one :)

Did some local testing which was promising! The file based cache consistently worked worked out to be under 1ms, whereas no caching took 11ms and database caching took 2-3ms.

[spawnia]

Testing in our integration environment looks promising too! In a particularly large query, using this shaved ~15ms off the execution time.

[thekonz]

Great results!
I remember that implementing the file based schema cache reduced execution time a bit as well, but mostly it reduced memory usage, because the value was already in opcache.
Have you checked out the difference in memory usage? Surely it won't be as substantial as the schema cache, but for a big query it should be nice.

[spawnia]

@thekonz Anything else before I merge and release?

[thekonz]

nope, looks good

[spawnia]

Released with https://github.com/nuwave/lighthouse/releases/tag/v6.63.0