Re: Pluggable Storage - Andres's take

On Tue, Apr 9, 2019 at 6:17 AM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:

> On 08/04/2019 20:37, Andres Freund wrote:
> > On 2019-04-08 15:34:46 +0300, Heikki Linnakangas wrote:
> >> There's a little bug in index-only scan executor node, where it mixes
> up the
> >> slots to hold a tuple from the index, and from the table. That doesn't
> cause
> >> any ill effects if the AM uses TTSOpsHeapTuple, but with my toy AM,
> which
> >> uses a virtual slot, it caused warnings like this from index-only scans:
> >
> > Hm. That's another one that I think I had fixed previously :(, and then
> > concluded that it's not actually necessary for some reason. Your fix
> > looks correct to me. Do you want to commit it? Otherwise I'll look at
> > it after rebasing zheap, and checking it with that.
>
> I found another slot type confusion bug, while playing with zedstore. In
> an Index Scan, if you have an ORDER BY key that needs to be rechecked,
> so that it uses the reorder queue, then it will sometimes use the
> reorder queue slot, and sometimes the table AM's slot, for the scan
> slot. If they're not of the same type, you get an assertion:
>
> TRAP: FailedAssertion("!(op->d.fetch.kind == slot->tts_ops)", File:
> "execExprInterp.c", Line: 1905)
>
> Attached is a test for this, again using the toy table AM, extended to
> be able to test this. And a fix.
>

It seems the two patches from email [1] fixing slot confusion in Index
Scans are pending to be committed.

1]
https://www.postgresql.org/message-id/e71c4da4-3e82-cc4f-32cc-ede387fac8b0%40iki.fi