Add paragraph on the performance of meta_queries using EXISTS/NOT_EXISTS about engineering-best-practices HOT 2 OPEN

@vishalkakadiya I think your solution should work fine. It taps into the same idea that is, always look for something that exists, instead of for something that doesn't. I suggest adding different values for a meta key, but having different meta-keys will most likely work just fine too.

I don't think indexing the meta_value column makes a lot of difference in this case, because the first thing the query will do is join the tables to contain only that meta_key. But then again, if we step into the millions of records within the join, then that might be a good replacement.

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@moraleida Hi 👋, you guys are doing awesome work with Engineering Practices! 🙌 Thank you for making these awesome docs.

I was recently checking this issue and would like to share my thoughts, not sure if this is a good idea for bigger picture but let me share:

• NOT EXISTS check: if the user makes a meta_key with appending _1 after the actual meta_key then it will be straight forward query to just check meta_key = _publicize_pending_1, so the end query will be as below:

$query = new \WP_Query(
	array(
		'suppress_filters' => true,
		'meta_key'         => '_publicize_pending_1',
	)
);

The above query will fetch all the posts which are pending for publicizing, and I guess will be somewhat faster than checking with the value. As we all know, in the normal WP environment index is available on meta_key only, not on the meta_value, however the WordPress VIP platform indexing meta_value in the combination of meta_key but in some limit of characters. So I guess we can think of this way as well for this issue, still correct me if I have interrupted in wrong discussions.

Thanks! 🙂

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