Horton

Re: SegFault on 9.6.14

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Thomas Munro <thomas.munro@gmail.com>, vignesh C <vignesh21@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Jerry Sievers <gsievers19@comcast.net>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-08-12T21:48:33Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> Being able to do that sort of thing was one of my goals in designing
> the ExecShutdownNode stuff.  Unfortunately, it's clear from this bug
> report that it's still a few bricks short of a load, and Tom doesn't
> seem real optimistic about how easy it will be to buy those bricks at
> discount prices. But I hope we persist in trying to get there, because
> I don't like the idea of saying that we'll never be smart enough to
> know we're done with any part of the plan until we're definitely done
> with the whole thing. I think that's leaving too much money on the
> table.

To clarify my position --- I think it's definitely possible to improve
the situation a great deal.  We "just" have to pass down more information
about whether rescans are possible.  What I don't believe is that that
leads to a bug fix that would be sane to back-patch as far as 9.6.

			regards, tom lane

Commits

  1. Don't shut down Gather[Merge] early under Limit.

  2. Prohibit shutting down resources if there is a possibility of back up.

  3. Fix buffer usage stats for parallel nodes.

  4. Fix crashes on plans with multiple Gather (Merge) nodes.

  5. Separate reinitialization of shared parallel-scan state from ExecReScan.