Re: Avoiding hash join batch explosions with extreme skew and weird stats

On Tue, Jul 30, 2019 at 2:47 PM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
> I did the "needlessly dumb implementation" Robert mentioned, though,
> I thought about it and couldn't come up with a much smarter way to
> write match bits to a file. I think there might be an optimization
> opportunity in not writing the current_byte to the file each time that
> the outer tuple matches and only doing this once we have advanced to a
> tuple number that wouldn't have its match bit in the current_byte. I
> didn't do that to keep it simple, and, I suspect there might be a bit
> of gymnastics needed to make sure that that byte is actually written
> to the file in case we exit from some other state before we encounter
> the tuple represented in the last bit in that byte.

I mean, I was assuming we'd write in like 8kB blocks or something.
Doing it a byte at a time seems like it'd produce way too many
syscals.

--
Robert Haas
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