Cache miss for `WP_Term_Query`

[Chouby]

On a WP fresh install (test made with WP 6.8.2).

1. Activate Query Monitor
2. Visit the posts list table
3. Check that Query Monitor report a duplicate query coming from WP_Term_Query::get_terms():

SELECT t.term_id
FROM wp_terms AS t
INNER JOIN wp_term_taxonomy AS tt
ON t.term_id = tt.term_id
WHERE tt.taxonomy IN ('category')
ORDER BY t.name ASC

One call is coming from wp_dropdown_categories()
One call is coming from wp_terms_check_list()

Both functions are not using the same arguments for the call to get_terms() but result in the same DB query.

In the past, the cache key used to be computed based on arguments passed to get_terms(). It's now ​a combination of these arguments and the SQL statement. Maybe using only the sql statement would be sufficient.

[westonruter]

Duplicate query confirmed

[westonruter]

I added some logging after the $key is generated:

<?php
do_action( 'qm/debug', compact( 'key', 'cache_args', 'sql' ) );

This is the difference between the logging for the duplicate queries:

/tmp/

@@ -1 +1 @@
 Array
 (
-    [key] => 7e29979b0d775b6021a8f36e13aae8e5
+    [key] => 5a24f652b8a6b799e1e6d7d7b6afceca
     [cache_args] => Array
         (
             [taxonomy] => Array
@@ -42 +42 @@
                 (
                 )
 
-            [hierarchical] => 
+            [hierarchical] => 1
             [search] => 
             [name__like] => 
             [description__like] => 
             [pad_counts] => 
-            [get] => all
+            [get] => 
             [child_of] => 0
             [parent] => 
             [childless] => 

My concern is that perhaps a different post-processed query result is being cached. However, by adding other logging when the cache is set, this doesn't seem to be the case:

/tmp/

@@ -1 +1 @@
 Array
 (
-    [cache_key] => get_terms:7e29979b0d775b6021a8f36e13aae8e5
+    [cache_key] => get_terms:5a24f652b8a6b799e1e6d7d7b6afceca
     [term_cache] => Array
         (
             [0] => 1

The cache key was most recently modified to remove a redundant parameter component in r59028, and previously in r55083.

Even back r37572 it was:

<?php
$key = md5( serialize( wp_array_slice_assoc( $args, array_keys( $defaults ) ) ) . serialize( $taxonomies ) . $query );

@Chouby When was the cache key just the SQL and not the args?

[Chouby]

To my knowledge, the arguments have always been included. The SQL was introduced in WP 4.4 by r35120

Keeping only the SQL was a suggestion for the future that could solve this duplicate queries issue.

[westonruter]

@Chouby ok, I was confused because in the description you said the args used to not be included:

In the past, the cache key used to be computed based on arguments passed to get_terms(). It's now ​a combination of these arguments and the SQL statement. Maybe using only the sql statement would be sufficient.

Maybe I misunderstood.