Horton

Re: Revert: Remove useless self-joins *and* -DREALLOCATE_BITMAPSETS make server crash, regress test fail.

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew@dunslane.net>, Richard Guo <guofenglinux@gmail.com>, jian he <jian.universality@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-05-08T22:07:22Z
Lists: pgsql-hackers 
On Thu, 9 May 2024 at 06:24, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I like alternative-2.patch a lot better, not least because it
> only adds cycles when join removal actually fires.  Basically
> this is putting the onus on the data structure modifier to
> cope with shared bitmapsets, rather than trying to say that
> sharing is disallowed.
>
> Thoughts?

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.

David

Commits

  1. Make left-join removal safe under -DREALLOCATE_BITMAPSETS.

  2. Revert: Remove useless self-joins

  3. Remove mention of nchar