Right. I think that upgrading psycopg2 etc. is still a good idea on general
principles, and I figured out the small amount of remaining glue to be able to
use a json column with Storm. However, there's still one difficult roadblock.
The approach I suggested in my previous comment of transforming
ResultSet.config(distinct=True) into
ResultSet.config(distinct=(DistroSeries.id,)) doesn't work in all cases when
ORDER BY is also involved. In such cases, PostgreSQL wants the DISTINCT ON
expressions to match the initial ORDER BY expressions, but then we have cases
like this in Distribution.derivatives:
ret = Store.of(self).find(
DistroSeries,
ParentDistroSeries.id == DistroSeries.previous_seriesID,
ParentDistroSeries.distributionID == self.id,
DistroSeries.distributionID != self.id)
return ret.config(
distinct=True).order_by(Desc(DistroSeries.date_created))
With Storm we can only easily have one ORDER BY, and they can't match in this
case. So it's very cumbersome to use DISTINCT ON here.
https://stackoverflow.com/a/24378258/989530 explains why this is hard. If we
had jsonb, we could use it and not have this problem. But we're still on
PostgreSQL 9.3, and lacking 9.4 or better, I think we should stick with text.
We still need to address the fact that DISTINCT will try to compare potentially
different serialisations of DistroSeries.publishing_options. I think the
simplest way to do this with 9.3 is just to add a patched version of
JSONVariable that uses json.dumps(sort_keys=True).
--
https://code.launchpad.net/~cjwatson/launchpad/db-distroseries-publishing-options/+merge/278241
Your team Launchpad code reviewers is requested to review the proposed merge of
lp:~cjwatson/launchpad/db-distroseries-publishing-options into
lp:launchpad/db-devel.
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