[wp-trac] [WordPress Trac] #49982: WP_User_Query returns duplicates if a user has multiple meta keys of the same name, unless "relation = OR" is included which adds DISTINCT

[WordPress Trac]

#49982: WP_User_Query returns duplicates if a user has multiple meta keys of the
same name, unless "relation = OR" is included which adds DISTINCT
--------------------------+-----------------------------
 Reporter:  radgh         |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Users         |    Version:  5.4
 Severity:  minor         |   Keywords:
  Focuses:                |
--------------------------+-----------------------------
 Hi,

 I ran into a bug that seems to be reproducible in core WP. It is possible
 that WP_User_Query returns duplicate results of users when they have
 multiple rows of matching metadata. I have a reproducible example.

 Have a user with the following metadata. And yes, this is silly duplicate
 metadata to begin with but the same would go for matching multiple
 conditions with add_user_meta() in realistic usage.

 user_id | meta_key | meta_value
 1 | program_tdw | Yes
 1 | program_tdw | Yes
 1 | program_tdw_status | certified
 1 | program_tdw_status | certified

 Use the following very basic meta query to get the users:

 {{{#!php
 <?php
 $query_args = array(
         'meta_query' => array(
                 'relation' => 'AND',

                 // Must have TDW program enabled, and TDW Status of
 Certified
                 array(
                         'key' => 'program_tdw',
                         'value' => 'Yes',
                 ),
                 array(
                         'key' => 'program_tdw_status',
                         'value' => 'certified',
                 ),
         ),
 );

 $users = new WP_User_Query( $query_args );
 }}}


 Your results will include User ID 1 two times, or potentially more times
 depending on how many specific meta key matches they have.

 An obvious fix is to use "DISTINCT" on the user id column that is
 returned, but there is no equivalent "posts_distinct" filter for
 WP_User_Query. There is currently a working hack to specify any "relation
 => OR" in the meta query.

 With that in mind my fix is to do this just before the last line:

 {{{#!php
 <?php
 $query_args['meta_query'] = array( 'relation' => 'OR',
 $query_args['meta_query'] );
 }}}

 Here is a related Stack Overflow question about the same topic from a few
 years ago: https://wordpress.stackexchange.com/questions/220307/user-
 appears-twice-in-a-wp-user-query

 It is probably minor but may have unexpected effects, like in my situation
 it was sending emails to some users twice. Imagine how difficult that was
 to debug the cause :(

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/49982>
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