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help / color / mirror / Atom feedFrom: Tomas Vondra <[email protected]>
To: Robert Haas <[email protected]>
Cc: bucoo <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: Tom Lane <[email protected]>
Subject: Re: optimize hashjoin
Date: Wed, 21 Aug 2024 21:51:38 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+TgmoZVEZ9-CD5gSzRzPrWbYYwnMb0sc-DPFsA19KkZBjibaQ@mail.gmail.com>
<div dir='auto'><div><div><div class="elided-text">On Aug 21, 2024 19:17, Robert Haas <[email protected]> wrote:<br type="attribution"><blockquote style="margin:0 0 0 0.8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr">On Wed, Aug 21, 2024 at 12:31 PM Tomas Vondra <[email protected]> wrote:
<br>
> Anyway, I took a look and the basic idea is simple - when shuffling
<br>
> tuples between batches in a hash join, we're currently deforming the
<br>
> tuple (->slot) we just read from a batch, only to immediately form it
<br>
> (slot->) again and write it to the "correct" batch.
<br>
<br>
Does skipping this cause any problem if some attributes are toasted?
<br>
<br>
I suppose not, just something to think about.
<br>
</p></blockquote></div></div></div><div dir="auto">I don't see why would this cause any such problems - if anything has to be done when forming the tuples, it had to be done the first time. Shuffling tuples to a different batch may happen, but AFAIK it's really just a copy.</div><div dir="auto"><br></div><div dir="auto"><div><div dir="auto">--</div><div dir="auto">Tomas Vondra</div></div></div></div>
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