Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin - Mailing list pgsql-hackers

On Wed, Jul 24, 2024 at 3:43 AM John Naylor <johncnaylorls@gmail.com> wrote:
>
> On Wed, Jul 24, 2024 at 5:40 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> > Without MEMORY_CONTEXT_CHECK, if size is 16 bytes, required_size is
> > also 16 bytes as it's already 8-byte aligned and Bump_CHUNKHDRSZ is 0.
> > On the other hand with MEMORY_CONTEXT_CHECK, the requied_size is
> > bumped to 40 bytes as chunk_size is 24 bytes and Bump_CHUNKHDRSZ is 16
> > bytes. Therefore, with MEMORY_CONTEXT_CHECK, we allocate more memory
> > and use more Bump memory blocks, resulting in filling up TidStore in
> > the test cases. We can easily reproduce this test failure with
> > PostgreSQL server built without --enable-cassert. It seems that
> > copperhead is the sole BF animal that doesn't use --enable-cassert but
> > runs recovery-check.
>
> It seems we could force the bitmaps to be larger, and also reduce the
> number of updated tuples by updating only the last few tuples (say
> 5-10) by looking at the ctid's offset. This requires some trickery,
> but I believe I've done it in the past by casting to text and
> extracting with a regex. (I'm assuming the number of tuples updated is
> more important than the number of tuples inserted on a newly created
> table.)

Yes, the only thing that is important is having two rounds of index
vacuuming and having one tuple with a value matching my cursor
condition before the first index vacuum and one after. What do you
mean update only the last few tuples though?

- Melanie