comment meta_query for keys that aren't yet set

Question

I need query help!

I am trying to set up a meta_query (for get_comments) for keys that aren't yet set.

I have some code that allows moderators to add a custom meta key to individual comments. Click the checkbox and the meta key is set to shadow, unclick it the meta key is set to an empty string.

This means that there are three possible states for a comment to have. It can either have the 'shadow' meta key, it can have an empty string and the meta key, or the meta key could not be set.

What I would like to do is query all comments that either don't have this meta key set or have the meta key that is NOT shadow. It is fairly easy to select all comments that have the meta key not equal shadow but I haven't found a away to also select comments that don't have the meta key set.

This is the code I am using, but it doesn't work. It selects every comment that has the meta key set, regardless of what it is set to.

            $comments = get_comments( array( 
                'meta_query' => array(
                    'relation' => 'OR',
                    array( // Select comments that don't have the 'shadow' p3_comment_status meta
                        'key' => 'p3_comment_status',
                        'value' => 'shadow',
                        'compare' => '!='
                    ),
                    array( // Select comments that don't have the p3_comment_status set
                        'key' => 'p3_comment_status',
                        'compare' => 'NOT EXISTS'
                    )
                )
                )
            );

Any help would be appricieated.

Thanks

UPDATE: For the record this is the code that ultimately worked for me:

            $comments = get_comments( array( 
                'order' => 'ASC',
                'post_id' => get_the_ID(),
                'meta_query' => array(
                    'relation' => 'OR',
                    array( // Select comments that don't have the 'shadow' p3_comment_status meta
                        'key' => 'p3_comment_status',
                        'value' => 'shadow',
                        'compare' => '!='
                    ),
                    array( // Select comments that don't have the p3_comment_status set
                        'key' => 'p3_comment_status',
                        'compare' => 'NOT EXISTS',
                        'value' => ''
                    )
                )
            ) );

The key was to set 'post_id' => get_the_ID()

Answer 1

You have no need for three states. Logically, you have "set" and "unset". Don't complicate things. When you check the box, add p3_comment_status. When you uncheck, remove (delete) the key. If you do that, all you need to do is use EXISTS/NOT EXISTS. That makes for a much simpler, and faster, query as a bonus.

You have not posted the code that saves your data so a detailed answer is not possible but delete_comment_meta is probably what you need.

Answer 2

For the record this is the code that ultimately worked for me:

            $comments = get_comments( array( 
                'order' => 'ASC',
                'post_id' => get_the_ID(),
                'meta_query' => array(
                    'relation' => 'OR',
                    array( // Select comments that don't have the 'shadow' p3_comment_status meta
                        'key' => 'p3_comment_status',
                        'value' => 'shadow',
                        'compare' => '!='
                    ),
                    array( // Select comments that don't have the p3_comment_status set
                        'key' => 'p3_comment_status',
                        'compare' => 'NOT EXISTS',
                        'value' => ''
                    )
                )
            ) );

The key was to set 'post_id' => get_the_ID()