Instead of prefetching post IDs to include or exclude via the searchwp_include or searchwp_exclude filters, you can directly integrate a meta_query into SearchWP's main search algorithm achieving the same result, but offloading the need to pass a (potentially huge) array of post IDs to include or exclude.

gistfile1.php

<?php

/*
 * In this particular implementation I am looking to limit the search results pool based on an
 * additional form field I have set up that allows people to search entries based on the number
 * of bedrooms, which is stored as post_meta with a meta_key of listing_bedrooms
 */

function my_searchwp_query_join( $sql, $engine ) {
	global $wpdb;
	$meta_query_args = array(
		array(
			'key'       => 'listing_bedrooms',
			'value'     => isset( $_GET["beds"] ) ? absint( $_GET["beds"] ) : 0,
			'compare'   => '>=',
			"type"      => "NUMERIC",
		)
	);
	$meta_query = new WP_Meta_Query( $meta_query_args );
	$mq_sql = $meta_query->get_sql(
		'post',
		$wpdb->posts,
		'ID',
		null
	);
	return $sql . $mq_sql['join'];
}

add_filter( 'searchwp_query_main_join', 'my_searchwp_query_join', 10, 2 );

function my_searchwp_query_conditions( $sql, $engine ) {
	global $wpdb;
	$meta_query_args = array(
		array(
			'key'       => 'listing_bedrooms',
			'value'     => isset( $_GET["beds"] ) ? absint( $_GET["beds"] ) : 0,
			'compare'   => '>=',
			"type"      => "NUMERIC",
		)
	);
	$meta_query = new WP_Meta_Query( $meta_query_args );
	$mq_sql = $meta_query->get_sql(
		'post',
		$wpdb->posts,
		'ID',
		null
	);
	return $sql . $mq_sql['where'];
}
 
add_filter( 'searchwp_where', 'my_searchwp_query_conditions', 10, 2 );

Hi! This worked great! Just wanted to ask if I can do this based on post type?

To explain, I have a custom field for the media/attachment post type. Basically a toggle to include or not include the PDFs in search.
So what I want to do is to still have a full search (post, pages, attachments), but when it comes to attachments, will filter only the ones tagged to be included in search. I tried the above, but of course, since posts and pages don't have that meta key/value, they also get excluded.

Just wanted to know if you have any thoughts on doing that kind of filter? Working on some other approaches, but maybe you guys already encountered a similar situation before. Thanks!