post_exists() results in a bad query

[apokalyptik]

The current post_exists() function in wp-admin/includes/post.php generates a poorly performing query (makes use of no indexes) This is basically a mirror issue to #33871 for all the same reasons.

The fix is a little bit different because post_date_gmt is actually not indexed and post_date is deep inside of a compound index...

KEY `type_status_date` (`post_type`,`post_status`(1),`post_date`,`ID`),

I have attached a diff to modify post_exists such that it can take post_type and post_status in addition to post_date and so make use of the existing table indexes. In my testing this is almost always 2x as fast in the optimal circumstance and massively faster in exceptionally poor circumstances.

[apokalyptik]

fix for post_exists() query performance

[DrewAPicture]

We're going to need ​unit tests for this.

[MikeHansenMe]

Adds basic tests and includes previous patch

[boonebgorges]

In 34680:

Add unit tests for post_exists().

Props MikeHansenMe.
See #34012.

[brettshumaker]

Updates patch and adds relevant unit tests.

[brettshumaker]

I have an updated patch for this ticket with some relevant unit tests.

I'd really like to see how we can move this forward, large sites using the WordPress Importer plugin would really benefit from this performance fix.

This is my first patch, but please let me know if there's anything else I can do.

[whyisjake]

Changes look good to me too. @SergeyBiryukov or @desrosj, any thoughts here?

[peterwilsoncc]

44314.diff​ is essentially @brettshumaker's patch with the following changes:

• Added a @since tag to the docblock for the new argument
• A few coding standards nitpicks fixed in the unit tests
• Added a couple of tests for post type and post status combos: both happy and unhappy paths

Adding the status parameter to improve the query makes sense to me.

Edit: Sorry about the bad ticket number in the file name.

https://core.trac.wordpress.org/ticket/34012

[peterwilsoncc]

In 51027:

Posts, Post Types: Improve post_exists() query.

Add $status parameter to post_exists() to allow developers to specify a post type, date and status to ensure they hit the wp_posts table's type_status_date index when determining if a post exists.

Props apokalyptik, boonebgorges, brettshumaker, DrewAPicture, MikeHansenMe, peterwilsoncc, whyisjake.
Fixes #34012.