Implemented very simple caching to avoid unnecessary database queries

[brocktimus]

I had some code which was calling #parent a lot. Rails :belongs_to caches this to avoid hitting the database unnecessarily. After migrating to ancestry I noticed it was much slower because every call to #parent resulted in the database being hit.

This is obviously an incredibly naive / trivial cache and doesn't bother to even try to cache the more complex methods.

We could make it an opt in argument passed to ::has_ancestry, but that seems really conservative.

Any idea how to test this? Can we assert on number of queries run? Otherwise I'll write a test now asserting on the object equality, potentially through #object_id.

[coveralls]

Coverage increased (+0.02%) when pulling 619ef0a on brocktimus:instance_method_optimizations into 46449bc on stefankroes:master.

[coveralls]

Coverage increased (+0.02%) when pulling c85c702 on brocktimus:instance_method_optimizations into 46449bc on stefankroes:master.

[vanderhoorn]

Not necessarily against project styles, but in general humans tend be better at seeing rather than reading.

If you see {} you know it is a new (empty) hash, but with Hash.new you would have to read to know it is a new hash.

:)

[coveralls]

Coverage increased (+0.02%) when pulling e25e7c0 on brocktimus:instance_method_optimizations into da7420f on stefankroes:master.

[kbrock]

I think this looks neat - but it makes me nervous.
I've seen a number of entity caching layers over the years for rails. They seem like such a good idea until they don't. Rails itself ended up going the caching sql route because they couldn't make it work.

I wonder if there is a way to optionally add this, as I'm leaning away from merging this.
But not against modifying the code to make this extension necessary.

[kbrock]

Rails has a standard mechanism for storing relationships in an object. This is cleared out when calling a reload!. Seems we should use the rails cache to store the values.

Also, with the introduction of rails 6.0, children.create no longer works without deprecations.
So I'm thinking we need to rework the way children is setup.

If we can turn it into a relationship, we gain a lot of great stuff. (like caching and eager includes)

[kbrock]

I'm currently trying to convert parent_id and ancestors as standard rails columns. I'm hoping that will lead us to being able to use standard associations (or slightly modified ones)