views api: $this->options['expose']['reduce'] = FALSE; ?

I'm trying to create a custom views filter handler and I was wondering what does the following do?
$this->options['expose']['reduce'] = FALSE;

Basically, I need a filter that comes up with options through a db_query. I think I can figure out how to do that, but I need to ensure that all options are available for selection. I was wondering what the piece of code above does and if it's related to enabling all the options for selection?