How to sort a selection (WP_Query) by a custom field after processing its value?

Question

WordPress

The bottom line is that in an arbitrary field I store a serialized array with data about the rating of the record, a simple array of the type:
array(
user_id_1 => number from 1 to 5,
user_id_2 => number from 1 to 5,
)
When the record is displayed, all this is considered and shown the average rating number is from 1 to 5.
The documentation has an example for sorting by a custom field, however, I need to sort not by the value of the field, but by its processed value. Is there something similar in WP?

Answer 1

If you need to perform such calculations, then you have architecturally incorrectly implemented. Such data should not be stored in postmeta, but in a separate table. Structure, roughly (let's call the table post_ratings):

id  |  post_id  |  user_id  |  rating
-------------------------------------
1   |  189      |  34       |  4

It is for this table that you make an initial selection with a miscalculation of the average rating and sorting, at the output you get a post_id list. You then pass them to WP_Query via the post__in parameter.
Alternatively, you can "cache" the average, already calculated, rating in the postmeta table, as a single int. Recalculate it either every time a new record is added to the custom table (by query or queued), or by cron once in a while.

Answer 2

well, make a variable, count in it, and put a variable in place of the value.