searching by keywords in post's metas or pagination links problem

Question

i wanna create a custom search that will search posts by keyword not only in their titles and/or contents, but in post metas.

for example, from $wp_query->query_vars['s'] i got a word 'plastic' after user clicked to search.

then i have 2 path to use it: add pre_get_posts action to filter all posts that have that keyword in metas or create a new query and then filter posts in template.

i know that first case - is the right case and i should use it, but i don't really understand how find filter posts by keywords in metas.

example code:

function d_search( $query ) {
    if ($query->is_search()) {
        $query->set( 'posts_per_page', 12 );
        $query->set('meta_query', array(
            array(
                'key'    => 'something',
                'value'  => $wp_query->query_vars['s'], //plastic
                'compare' => 'LIKE'
            )
        ));
    }
}
add_action( 'pre_get_posts', 'd_search' );

my meta post with key 'something' has value 'plastic love' and as you can see my query_vars['s'] or 'plastic' is in 'plastic love' line.

why it doesnt work? just doesn't filter anything.

and in seconds case:

when i'm using my another case i have a search page http://localhost/search. i have filtered posts in global query, i have a pagination.

every button's link in pagination looks like http://localhost/search/plastic/page/2/and it doesn't work. if i open it, i just see my 404 template.

if i use http://localhost/search/plastic?paged=2 it won't work too.

how can i use first case or how can i fix second problem? (please, no plugins)

Answer 1

Okay. I solved it by myself. i dunno what's wrong, but it looks like using first case - just doesn't work. using second case - is a bad idea.

so i began to work with sql and posts_where commands.

first: instead of $wp_query->query_vars['s'] i started to use get_search_query()

second: looks like when sql tries to compare meta_value with value, it asks for %. yes, so in sql code you should write something like:

wp_postmeta.meta_key LIKE \'_entitle\' AND wp_postmeta.meta_value LIKE \'%' . get_search_query() . '%\'

third: because you are using wp_postmeta, you must join its posts ids with ids from wp_posts:

function dasdasd( $join, $query ) {
    global $wpdb;

    if ( is_search() ) {    
        $join = 'INNER JOIN wp_postmeta ON ( wp_posts.ID = wp_postmeta.post_id )';
    }

    return $join;
}
add_filter('posts_join', 'dasdasd', 10, 2 );

and fourth: i dunno why but you must add groupby code:

add_filter( 'posts_groupby', 'adadad', 10, 2 );

function adadad( $groupby, $query ){
    $groupby = 'wp_posts.ID';

    return $groupby;
}

i would like to know what's wrong with fourth step and why groupby's existing is so important for search query. thank you.