Can I specify post__in for one particular post type in the query?

I want to do something like this

$query_args = array(
    'post_type' => array( 'cpt_1', 'cpt_2' ),
    'post__in' => array( 1, 3, 5, 7 )
);

where I can specify which post type the post__in applies to.

For example, I want to get all the posts from cpt_1, but I only want the cpt_2 ones that are specified in post__in. Is there an SQL hook (like posts_where) that can help me accomplish this? If not I guess I’ll have to do two queries?

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Method 1

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Method 1

WP_Query is not capable of that kind of logic without a lot of help. There are a few things you can do though:

Just run two distinct queries, one for each post type. This is simple and quick but your posts aren’t “mixed” together. I don’t know if that is what you want. You’d then need two separate Loops as well. I am sure you can set this up so I am not posting code for it.

Run multiple queries and combine them.

$post_ids = new WP_Query(array(
  // query for one post type
  'fields' => 'ids',
  // other parameters
));

$post_ids_2 = new WP_Query(array(
  // query for the others
  'fields' => 'ids',
  // other parameters
));
// join them
$post_ids = $post_ids->posts + $post_ids_2->posts;
$posts_qry = new WP_Query(array('post__in'=> $posts_ids));

There is a performance issue with this technique as you need to run three queries to make it work. Your posts are intermingled and you can use one Loop to display them.

Write a lot of SQL– ie. a UNION (Code stolen form another post so it is illustrative only. You will need to alter it.)

$sql = "(SELECT ID FROM {$wpdb->posts} WHERE post_type = 'books' AND post_status = 'publish' LIMIT 3)
UNION ALL
(SELECT ID FROM {$wpdb->posts} WHERE post_type = 'magazines' AND post_status = 'publish' LIMIT 2)
UNION ALL
(SELECT ID FROM {$wpdb->posts} WHERE post_type = 'videos' AND post_status = 'publish' LIMIT 1)";
// be sure to add any other conditions you need
$ids = $wpdb->get_col($sql);

Now the fun part– filters. You will need post_fields,
posts_join, and posts_where to do this, or posts_clauses. The
latter is by far the simplest.

function post_in_one_type($clauses) {
  remove_filter('posts_clauses','post_in_one_type');
  global $wpdb;

  $clauses['fields'] .= ', cpt2.*';
  $clauses['join'] .= ", {$wpdb->posts} as cpt2 ";
  $where = preg_match(
    "/ AND (.*)/",
    $clauses['where'],
    $matches
  );

  $cpt2_where = str_replace($wpdb->posts,'cpt2',$matches[1]);
  $cpt2_where = str_replace('cpt_1','cpt_2',$cpt2_where).' AND cpt2.ID IN (1, 3, 5, 7) ';
  $clauses['where'] = ' AND ('.$matches[1].') || ('.$cpt2_where.') ';

  return $clauses;
}
add_filter('posts_clauses','post_in_one_type');
$args = array(
    'post_type' => array( 'cpt_1' )
);
$q = new WP_Query($args);
var_dump($q->request);

It is nearly impossible to test that effectively so no promises. I would try the other solutions first and stick with them unless you really see a performance hit that you just cannot bear.

https://wordpress.stackexchange.com/a/79960/21376
https://wordpress.stackexchange.com/a/79977/21376

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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