| From: | Frédéric Yhuel <frederic(dot)yhuel(at)dalibo(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com> |
| Cc: | Andreas Karlsson <andreas(at)proxel(dot)se>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: pgstattuple: fix free space calculation |
| Date: | 2024-09-09 13:49:54 |
| Message-ID: | b1d09192-7934-40fb-8221-ef2df42efa45@dalibo.com |
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| Lists: | pgsql-hackers |
On 9/7/24 22:45, Tom Lane wrote:
> I wrote:
>> Now alternatively you could argue that a "new" page isn't usable free
>> space yet and so we should count it as zero, just as we don't count
>> dead tuples as usable free space. You need VACUUM to turn either of
>> those things into real free space. But that'd be a bigger definitional
>> change, and I'm not sure we want it. Thoughts?
>
> On the third hand: the code in question is in statapprox_heap, which
> is presumably meant to deliver numbers comparable to pgstat_heap.
> And pgstat_heap takes no special care for "new" pages, it just applies
> PageGetHeapFreeSpace (or PageGetExactFreeSpace after this patch).
> So that leaves me feeling pretty strongly that this whole stanza
> is wrong and we should just do PageGetExactFreeSpace here.
>
+1
v4 patch attached.
Best regards,
Frédéric
| Attachment | Content-Type | Size |
|---|---|---|
| v4-0001-pgstattuple-use-PageGetExactFreeSpace.patch | text/x-patch | 3.2 KB |
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