On Thu, May 18, 2023 at 04:03:36PM -0400, Tom Lane wrote:
> Yeah. I see the problem: when starting up an EPQ recheck, we stuff
> the tuple-to-test into the epqstate->relsubs_slot[] entry for the
> relation it came from, but we do nothing to the EPQ state for the
> other target relations, which allows the EPQ plan to fetch rows
> from those relations as usual. If it finds a (non-updated) row
> passing the qual, kaboom! We decide the EPQ check passed.
Ah, so the EPQ check only fails for the last tuple because we won't fetch
rows from the other relations. I think that explains the behavior I'm
seeing.
> What we need to do, I think, is set epqstate->relsubs_done[] for
> all target relations except the one we are stuffing a tuple into.
This seems generally reasonable to me.
> While nodeModifyTable can certainly be made to do that, things are
> complicated by the fact that currently ExecScanReScan thinks it ought
> to clear all the relsubs_done flags, which would break things again.
> I wonder if we can simply delete that code. Dropping the
> FDW/Custom-specific code there is a bit scary, but on the whole that
> looks like code that got cargo-culted in rather than anything we
> actually need.
I see that part was added in 385f337 [0]. I haven't had a chance to
evaluate whether it seems necessary.
[0] https://postgr.es/m/9A28C8860F777E439AA12E8AEA7694F80117370C%40BPXM15GP.gisp.nec.co.jp
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
