Display facets when there are no search results

Does the search_api_facets_always option actually exist or did you just invent it?
In the latter case: why?
In any case, it seems this can be much easier be implemented by just moving the facets code out of the enclosing if?

Anyways, if we do that, we’ll decrease performance for queries with empty results sets even in the vast majority of cases where there won’t be any facets. So, I think we should take this opportunity to finally optimize the getFacets() code a bit.

Patch attached, please test/review!
(I completely reverted your changes, so no interdiff.)

+++ b/modules/search_api_db/src/Plugin/search_api/backend/Database.php
@@ -2374,8 +2376,33 @@ protected function getFacets(QueryInterface $query, SelectInterface $db_query) {
+        if (isset($result_count) && $result_count < $facet['min_count']) {

I would prefer to do if ($result_count !== NULL && ...) instead.
Are we sure that this is <, and not =<? I'm not sure I am.

Otherwise the changes here look very good and I think they are an improvement. I would like to run facets tests with this patch enabled first though. Doing that now locally and I'll get back with the results.

The tests are still green, so that's nice. I think we can get this in - depending on the result of my other comments in #4.

I would prefer to do if ($result_count !== NULL && ...) instead.

Hm, yes, so would I.

Are we sure that this is <, and not =<? I'm not sure I am.

Yes. If there is 1 result and min-count is 2, we can’t possibly have any facets. If min-count is 1, we can.

@drunken monkey, the search_api_facets_always is requested/added in Display facets when there are no search results.

And is that patch needed for facets to be displayed, or does it just work with this patch, too?

I've tested the patch of #3, and in my setup I combine facets with free text search. When I enter some keywords in the search field that don't produce any results and than select a facet checkbox, all facet options are lost again (so, I'm also not able to deselect it).

Can’t reproduce that, and don’t see why that would happen. The minimum count of 0 should be in effect both before and after selecting a facet filter.

But I guess we still need tests for this anyways, so adding those, too. (Before Joris can complain again. ;P)

Awesome, thanks for that! This feature has been requested a couple of times in facets - and I think that this implementation makes more sense than some others I've seen/heard before.

Alright, thanks for your feedback!
Committed.
Thanks again, everyone!

Is it just me or it's not working ? Used with Drupal core 9.2.0, Search Api 1.20 and Facets 1.8. Settings of my facet:

• taxonomy field
• checkbox widget
• operator OR
• minimum count 0

@Lus if you were using operator "and" the further discussion in the issue might have been the reason: #2993101: Display facets when there are no search results but in your constellation, I don't have an explanation so far.

@drunken monkey, @borisson_, @Watergate, sadly after this has been committed, there was no more progress or documentation over at #2993101: Display facets when there are no search results. Please also help to get this done over there cleanly. That would be great.