WP_Query: sort more arrays to improve cache hits.

[peterwilsoncc]

Lighter touch alternative to #5347

What

Improves the cache hits for WP_Query

How

It sorts query variable whenever possible. This results in the SQL queries being normalised so that it doesn't produce different SQL for the same effective arguments. For example category__in => [1,2] and category__in => [2,1] produce the same IN() clause.

Why

Currently the SQL queries and the generated cache key differ for the same effective arguments.

Trac ticket: https://core.trac.wordpress.org/ticket/59516

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[github-actions]

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[kt-12]

@peterwilsoncc I was concerned that sorting might effect the order of the output too, looks like it doesn't. Can we also ensure, https://core.trac.wordpress.org/ticket/59492#comment:3 is handled (if not), please. If there is only one element in the array it should be converted into string. I remember getting that scenario from a live site, but I can't recall the details.

[peterwilsoncc]

I was concerned that sorting might effect the order of the output too, looks like it doesn't.

The order should only have an effect for items that can be used for the orderby clause, for example post__in. It's fine to sort for the where clause so the key differs only in the instances where the item is used for ordering.

Can we also ensure, https://core.trac.wordpress.org/ticket/59492#comment:3 is handled (if not), please. If there is only one element in the array it should be converted into string. I remember getting that scenario from a live site, but I can't recall the details.

My recollection is that in some instances the use of a string vs an array can result in a different where clause beyond just the use of = vs IN. At the very least, I know it is complicated so I'm trying to get something lighter touch in initially so it's possible to spend additional time comparing the effect of passing a string or an array.

[peterwilsoncc]

These two are failing. cat is normalised in the generated SQL query but not in the arguments passed to ::generate_cache_key().

I can't figure out why as the query vars are passed to ::parse_term_query() by reference so sorting it there should work. @joemcgill Can you see what I am missing?

[peterwilsoncc]

These two are failing. cat is normalised in the generated SQL query but not in the arguments passed to ::generate_cache_key().

I can't figure out why as the query vars are passed to ::parse_term_query() by reference so sorting it there should work. @joemcgill Can you see what I am missing?

nvm, the tests were testing the wrong thing so I've started testing the cache key generated by WP_Query in bc24627

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