If Relevanssi Premium causes out of memory problems, make sure you have the “Throttle searches” option checked.
However, if that doesn’t work, and you’re still getting out of memory issues, you can try making the throttle tighter. The limit can be adjusted by adding this line to your theme functions.php file:
add_filter( 'pre_option_relevanssi_throttle_limit', function( $limit ) { return 250; } );You can adjust the value (250) to a lower number if necessary. Anything over 100 should be safe what comes to the search finding the most relevant posts.