[5.x] Ensure no queries are run when entries field has no values

[ryanmitchell]

Following the suggested approach here, this PR introduces an EmptyQueryBuilder which is returned by the Entries field type when there are no results to return.

This ensures no query is actually run, which is a performance win.

@jasonvarga If this is what you intended then should I roll it out to the terms and assets fieldtypes?

Closes #11152.

[jasonvarga]

Nice!

There's also another place where this would come in handy, and I'd like to be able to handle it. I can't quite remember where though. I'll try to track it down.

I'm pretty sure it's when you're within a query already somewhere and a certain clause would trigger no results, so avoiding an actual query would be good there. 🤔

It would be good to nail the pattern first before rolling it out to other places.

[jasonvarga]

Ah, it's here:

cms/src/Stache/Query/QueriesEntryStatus.php

Line 38 in 8658bb5

$query->where('date', 'invalid'); // intentionally trigger no results.

[ryanmitchell]

@jasonvarga I don't love it, but this gets around it being inside a where function clause.

Though returning the empty builder isnt even needed, it could just not do the orWhere() entirely

[jasonvarga]

Maybe a bit of a pain, but I think we'll need multiple empty builder classes.

e.g. an EmptyEntryQueryBuilder that implements Statamic\Contracts\Entries\EntryQueryBuilder. One for assets, terms, etc.

Otherwise, someone might be expecting or typehinting EntryQueryBuilder and would now fail if they're given an EmptyQueryBuilder.

They can probably be empty classes and all share a trait with no-op methods.

I'm happy to take over this PR if you want.

[ryanmitchell]

Always happy to make it better.

I've refactored it to have a base EmptyQueryBuilder with a new EmptyEntryQueryBuilder which implements Statamic\Contracts\Entries\QueryBuilder. For completeness I've also ensured the EmptyEntryQueryBuilder supports the taxonomy where clauses, though as no results are returned it doesn't actually do anything.

Happy to move to a trait if you think thats better, but the EmptyQueryBuilder class might be useful in and of itself.

[yurichudaev]

I apologize for being persistent, but I need to launch a website for a major regional bank next week. Will the PR be completed by then, or should I proceed with refactoring the code?

[jasonvarga]

Sorry but we can't promise an ETA unfortunately.

You might be able to workaround it by overriding Statamic\Fieldtypes\Entries and add an early return to the augment method between these lines.

cms/src/Fieldtypes/Entries.php

Lines 369 to 371 in ed9161d

	}
	$query = $this->queryBuilder($values);

Something like

if (empty($values)) {
    return null;
}