| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | John R Pierce <pierce(at)hogranch(dot)com> |
| Cc: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Vacuum full: alternatives? |
| Date: | 2016-06-20 15:51:51 |
| Message-ID: | CAKFQuwavBni1b3TYkpNR71QkmCifpaOEAguihked62MwbwrT4g@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
On Monday, June 20, 2016, John R Pierce <pierce(at)hogranch(dot)com> wrote:
> On 6/20/2016 8:03 AM, Scott Mead wrote:
>
>>
>> I believe that free space is only available to UPDATE, not INSERT.
>>
>
> incorrect. in fact, an update is performed identically to an INSERT +
> DELETE(old)
>
>
Except for heap-only-tuple optimization, right? We cannot build a HOT
chain if the user requests a delete separately since their is no longer an
association to trace from the old record.
I suspect this affects free space usage to some degree as well but I agree
and believe that the reclaimed space is not forbidden to be used (I
wouldn't rely on my word though and haven't tried to find relevant
documentation).
David J.
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