Problem When Using Object Caching

julien731
(@julien731)

9 years, 9 months ago
I have been running into an issue that occurs when CPT-onomies is used on a site that has object caching enabled. This is a pretty big issue as it basically breaks the plugin.

Also, I should add that the problem occurs when terms are requested more than once per runtime.

Here is what happens with object caching and multiple requests for CPT-onomies:
- Terms queried via get_the_terms()
- It is the first run so the object cache is empty. wp_get_object_terms() is ran
- wp_get_object_terms() queries the database and doesn’t find anything, populates object cache with blanks/errors
- CPT-onomies hooks at the end of wp_get_object_terms() and does its own querying, returns “correct” results
- get_the_terms() returns correct results
On the first run, all is fine. However, if a second run is triggered:
- get_the_terms() checks object cache (relationships) which isn’t empty anymore
- Runs get_term() on each term. Because the terms don’t actually exist in the database, the function returns a Invalid Term error
- Returns the error, never runs wp_get_object_terms() and thus never runs the CPT-onomies filters
It is basically impossible to use the plugin in this particular scenario.

https://ww.wp.xz.cn/plugins/cpt-onomies/

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Thread Starter

(@julien731)

Because I am currently working on a project that has to go live very soon, I have written a (dirty) workaround that basically bypasses the object cache. It is not good, but for now it works. I will be looking for a real solution later on.

add_filter( 'get_the_terms', 'cpt_onomies_object_cache_workaround', 10, 3 );
/**
 * Clear CPT-onomies terms relationships object cache
 *
 * There is a bug in CPT-onomies that breaks the plugin when get_the_terms() is ran more than once and object caching
 * is enabled. I have reported the bug on the support forum
 * (https://ww.wp.xz.cn/support/topic/problem-when-using-object-caching?replies=1#post-8775025).
 *
 * Because the site needs to go live fast, this workaround will be used for now. It is definitely dirty and should be
 * removed when a real fix comes up.
 *
 * @param  array|WP_Error $terms    List of attached terms, or WP_Error on failure.
 * @param  int            $post_id  Post ID
 * @param  string         $taxonomy The taxonomy name
 *
 * @return array|WP_Error           Un-altered terms
 */
function cpt_onomies_object_cache_workaround( $terms, $post_id, $taxonomy ) {

	// Only delete the cache for my custom CPT-onomies
	if ( in_array( $taxonomy, array( 'my_cptonomies' ) ) ) {
		wp_cache_delete( $post_id, $taxonomy . '_relationships' );
	}

	return $terms;

}

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