Re: BUG #14169: Incorrect merge join result in 9.5

On Wed, Jun 1, 2016 at 11:10 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> yancya@upec.jp writes:
>> TRAP: FailedAssertion("!(compareResult < 0)", File: "nodeMergejoin.c", Line: 942)
>
> This is not a mergejoin logic bug, because nodeMergejoin.c didn't change
> significantly between 9.4 and 9.5.  It must be that the input data is not
> being delivered in the expected order.  I first thought that Peter G's
> sorting optimizations must be at fault, but if you run either of the
> mergejoin's subplans in isolation, you get correctly sorted data.  What
> must be happening, then, is that mergejoin's mark/restore operations are
> confusing the btree indexscan and causing it to deliver the wrong tuple(s)
> after a restore.
>
> Armed with that conclusion about where the bug probably is, I looked
> through the git history, and soon found that the crash goes away if
> I manually revert commit 2ed5b87f96d473962ec5230fd820abfeaccb2069.
>
> In short: Kevin, you broke mark/restore.  Please fix.

I'm on it.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company