| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org, Virender Singla <virender(dot)cse(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: TOAST - why separate visibility map |
| Date: | 2021-11-20 16:16:22 |
| Message-ID: | 3172107.1637424982@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On November 19, 2021 12:31:00 PM PST, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> It might be feasible to drop the visibility map for toast tables, though.
> I think it be a bad idea - the VM is used by vacuum to avoid rereading already vacuumed ranges. Loosing that for large toast tables would be bad.
Ah, right. I was thinking vacuuming depended on the other map fork,
but of course it needs this one.
In short, there are indeed good reasons why it works like this.
regards, tom lane
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