Duplicate query in WP_Query

[spacedmonkey]

When a site using a classic theme and has sticky posts, that can result in duplicate query. ( See attached screenshot ). This is because post_type variable passed the sticky sub query, is empty string on the first run. See the ​line. This results in different cache query key being generating, resulting in duplicate queries.

Steps to replicate.

1. Set theme to 2016.
2. Import theme data test data.
3. Go to home page.
4. Open query monitor, see duplicate query.

Trac ticket: https://core.trac.wordpress.org/ticket/59442

One nice side effect of this change, is this line will not have an empty string.

​https://github.com/WordPress/wordpress-develop/blob/4ae2d1a533c6f6dc3b7d82505763dc732924e0f0/src/wp-includes/class-wp-query.php#L3536

[hellofromTonya]

As this is touching WP_Query, I'm thinking it needs to be an early candidate. Why? Touching it is risky. Committing early in the alpha cycle gives a long soak time for follow-ups, testing, and feedback. Touching it during the 6.4 Beta cycle makes me nervous.

@spacedmonkey is this fix critical for 6.4? What do you think of moving it to early 6.5?

[thekt12]

One of the main reason we get multiple queries for the same SQL is the hash takes serialised args as string for hashing, leading to a different key for even slightest of change in args.

I have documented it in ->
https://core.trac.wordpress.org/ticket/59492

Following PR, solves the current issue along with possibility of any more duplicates in different scenerio.
​https://github.com/WordPress/wordpress-develop/pull/5347/files

[thekt12]

Sticking to the original problem, this PR ​https://github.com/WordPress/wordpress-develop/pull/5295 fixes the issue.

[spacedmonkey]

PR looks good to me. Marking as ready to commit.

[spacedmonkey]

Based on feedback from @hellofromTonya and @joemcgill I am going to punt this to WP 6.5. Marking as early, in hope of commit early and giving the whole release cycle to test. Assigning to Joe to own.