I was looking over Ecto and CockroachDB issue: (CaseClauseError) no case clause matching - #9 by Ankhers
The basic need we have is that we need many select queries such as this:

SELECT x, y, z
FROM foobar f
WHERE f.x = 'some-condition';

to be modified to include AS OF SYSTEM TIME, like this:

SELECT x, y, z
FROM foobar f
AS OF SYSTEM TIME '-5m'
WHERE f.x = 'some-condition';

These are called follower reads by Cockroach – it’s important to specify this to avoid data sync errors and to take advantage of reading from replicas. It basically allows the query to say “it’s ok if the data is x minutes old”.

The problem is that when Ecto generates the query or renders a fragment, the clauses appear in ways that are considered invalid (from Cockroach’s point of view). I’ve tried a few different things here including the fragment example in the other post as well as including literal clauses, but so far, I haven’t found a winning combination. It would be possible to come up with my own alternative to the from macro, but I’m hoping there’s an easier way.

Thanks in advance for any pointers!