Wordpress, multiple meta_key in pre_get_posts

Question

is it possible to add two meta_key\'s in pre_get_posts?

my current query

$query->set(\'s\', \'\' ); 
$q         


        

Answer 1

You can convert this query to pre_pget_posts:

$meta_query_args = array(
    'relation' => 'AND', // "OR"
    array(
        'key'     => '_my_custom_key',
        'value'   => 'Value I am looking for',
        'compare' => '='
    ),
    array(
        'key'     => '_your_min_model_key',
        'value'   => 1453,
        'compare' => '>'
    ),
    array(
        'key'     => '_your_max_model_key',
        'value'   => 1923,
        'compare' => '<'
    )
);
$meta_query = new WP_Meta_Query( $meta_query_args );

And compare param details:

compare (string) - Operator to test. Possible values are '=', '!=', '>', '>=', '<', '<=', 'LIKE', 'NOT LIKE', 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN', 'EXISTS' (only in WP >= 3.5), and 'NOT EXISTS' (also only in WP >= 3.5). Values 'REGEXP', 'NOT REGEXP' and 'RLIKE' were added in WordPress 3.7. Default value is '='. 

Answer 2

To combine the two parts, you can try the following:

add_action( 'pre_get_posts', function( $q ) {    

    // Only modify the main query on the front-end:
    if( ! is_admin() && $q->is_main_query() )
    {
        $meta_query = array(
          array(
            'key'     => 'cat_adresse_stadtteil',
            'value'   => array('charlottenburg', 'wilmersdorf', 'schmargendorf'),
            'compare' => 'IN',
          ),
        );
        $q->set( 'meta_query', $meta_query      );
        $q->set( 'meta_key',   'rank'           );
        $q->set( 'orderby',    'meta_value_num' );
        $q->set( 'order',      'ASC'            );
        $q->set( 's',          ''               );
    }
});

It looks like you were missing the compare parameter and using the order and orderby parameters in a wrong place. I'm not sure though why you are resetting the search parameter.

The generated SQL query will look something like:

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID
    FROM wp_posts 
    INNER JOIN wp_postmeta
        ON (wp_posts.ID = wp_postmeta.post_id)
    INNER JOIN wp_postmeta AS mt1
        ON (wp_posts.ID = mt1.post_id)
    WHERE 1=1 
        AND wp_posts.post_type 
            IN ('post', 'page', 'attachment' )
        AND (wp_posts.post_status = 'publish'
            OR wp_posts.post_author = 1
            AND wp_posts.post_status = 'private')
        AND (wp_postmeta.meta_key = 'rank'
        AND (mt1.meta_key = 'cat_adresse_stadtteil'
        AND CAST(mt1.meta_value AS CHAR) 
            IN ('charlottenburg','wilmersdorf','schmargendorf')) )
    GROUP BY wp_posts.ID
    ORDER BY wp_postmeta.meta_value+0 ASC
    LIMIT 0, 10