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help / color / mirror / Atom feedFrom: Richard Guo <[email protected]>
To: Tom Lane <[email protected]>
Cc: David Rowley <[email protected]>
Cc: Andrew Dunstan <[email protected]>
Cc: jian he <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Revert: Remove useless self-joins *and* -DREALLOCATE_BITMAPSETS make server crash, regress test fail.
Date: Thu, 9 May 2024 10:43:31 +0800
Message-ID: <CAMbWs49fy=f-jCd7s33d9AGjnYZn6R8TEDU6armi7Yo6QHCKiw@mail.gmail.com> (raw)
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On Thu, May 9, 2024 at 6:40 AM Tom Lane <[email protected]> wrote:
> David Rowley <[email protected]> writes:
> > I'm fine with this one as it's the same as what I already mentioned
> > earlier. I had imagined doing bms_del_member(bms_copy ... but maybe
> > the compiler is able to optimise away the additional store. Likely, it
> > does not matter much as pallocing memory likely adds far more overhead
> > anyway.
>
> I actually wrote it that way to start with, but undid it after
> noticing that the existing code in remove_rel_from_restrictinfo
> does it in separate steps, and thinking that that was good for
> both separation of concerns and a cleaner git history. I too
> can't believe that an extra fetch will be noticeable compared
> to the cost of the adjacent bms_xxx operations.
I also think it seems better to do bms_copy in separate steps, not only
because this keeps consistent with the existing code in
remove_rel_from_restrictinfo, but also because we need to do
bms_del_member twice for each lefthand/righthand relid set.
Speaking of consistency, do you think it would improve the code's
readability if we rearrange the code in remove_rel_from_query so that
the modifications of the same relid set are grouped together, just like
what we do in remove_rel_from_restrictinfo? I mean something like:
sjinf->min_lefthand = bms_copy(sjinf->min_lefthand);
sjinf->min_lefthand = bms_del_member(sjinf->min_lefthand, relid);
sjinf->min_lefthand = bms_del_member(sjinf->min_lefthand, ojrelid);
...
Thanks
Richard
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To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: Revert: Remove useless self-joins *and* -DREALLOCATE_BITMAPSETS make server crash, regress test fail.
In-Reply-To: <CAMbWs49fy=f-jCd7s33d9AGjnYZn6R8TEDU6armi7Yo6QHCKiw@mail.gmail.com>
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