Do Seeded Orderby Rand Queries Benefit from DB Caching?

Question

I'm aware that various object caching plugins give you the benefit of caching results from frequent database queries. So that repeated queries return a cached result set rather than running the query again.

I've also heard that using Orderby => Rand repeats queries and doesn't allow caching because the results change every time.

Am I correct in assuming that if I use the seed rand(x) Orderby, such as a date as an integer, I can benefit from caching? Has anyone tested this?

Answer 1

Looking at the source of class-wp-query.php (ie, the WP_Query code), I find this:

        /*
         * Ensure the ID database query is able to be cached.
         *
         * Random queries are expected to have unpredictable results and
         * cannot be cached. Note the space before `RAND` in the string
         * search, that to ensure against a collision with another
         * function.
         *
         * If `$fields` has been modified by the `posts_fields`,
         * `posts_fields_request`, `post_clauses` or `posts_clauses_request`
         * filters, then caching is disabled to prevent caching collisions.
         */
        $id_query_is_cacheable = ! str_contains( strtoupper( $orderby ), ' RAND(' );

...which suggests that, even with seeded randomness à la RAND(x), the query won't get cached.