Add relevance weight to a single SearchWP Source (Posts)

searchwp-customizations.php

<?php

// @link https://searchwp.com/documentation/knowledge-base/comparing-index-source-mods/
// Add relevance weight to a single SearchWP Source (Posts).
add_filter( 'searchwp\query\mods', function( $mods ) {
	global $wpdb;

	$mod = new \SearchWP\Mod();
	$source = \SearchWP\Utils::get_post_type_source_name( 'post' );
	$mod->weight( $wpdb->prepare( "IF(s.source = %s, 9999999, 0)", $source ) );

	$mods[] = $mod;

	return $mods;
} );