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help / color / mirror / Atom feedFrom: Stephen Frost <[email protected]>
To: Elizabeth Christensen <[email protected]>
Cc: [email protected]
Subject: Re: [PATCH] updates to docs about HOT updates for BRIN
Date: Mon, 26 Feb 2024 18:28:42 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CABoUFXRjisr58Ct_3VsFEdQx+fJeQTWTdJnM7XAp=8MUbtoa9A@mail.gmail.com>
<Zd0O8CqQM1ms/[email protected]>
<[email protected]>
Greetings,
* Elizabeth Christensen ([email protected]) wrote:
> > On Feb 26, 2024, at 4:21 PM, Stephen Frost <[email protected]> wrote:
> > * Elizabeth Christensen ([email protected]) wrote:
> >> I have a small documentation patch to the HOT updates page
> >> <https://www.postgresql.org/docs/current/storage-hot.html>to add references
> >> to summary (BRIN) indexes not blocking HOT updates
> >> <https://www.postgresql.org/message-id/[email protected]...;,
> >> committed 19d8e2308b.
> >
> > Sounds good to me, though the attached patch didn't want to apply, and
> > it isn't immediately clear to me why, but perhaps you could try saving
> > the patch from a different editor and re-sending it?
>
> Thanks Stephen, attempt #2 here.
Here's an updated patch which tries to improve on the wording a bit by
having it be a bit more consistent. Would certainly welcome feedback on
it though, of course. This is a tricky bit of language to write and
a complex optimization to explain.
Thanks!
Stephen
Attachments:
[text/x-diff] v3-0001-Adding-Summary-Index-Info-to-HOT-Update-Documentatio.patch (2.7K, ../[email protected]/2-v3-0001-Adding-Summary-Index-Info-to-HOT-Update-Documentatio.patch)
download | inline diff:
From bb88237d1f807572a496ff2a267ab56bef61ac8e Mon Sep 17 00:00:00 2001
From: Stephen Frost <[email protected]>
Date: Mon, 26 Feb 2024 17:17:54 -0500
Subject: [PATCH] docs: Update HOT update docs for 19d8e2308b
Commit 19d8e2308b changed when the HOT update optimization is possible
but neglected to update the Heap-Only Tuples (HOT) documentation. This
patch updates that documentation accordingly.
Author: Elizabeth Christensen
Reviewed-By: Stephen Frost
Backpatch-through: 16
Discussion: https://postgr.es/m/CABoUFXRjisr58Ct_3VsFEdQx+fJeQTWTdJnM7XAp=8MUbtoa9A@mail.gmail.com
---
doc/src/sgml/storage.sgml | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 3ea4e5526d..d6c53a8d25 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -1097,8 +1097,11 @@ data. Empty in ordinary tables.</entry>
<itemizedlist>
<listitem>
<para>
- The update does not modify any columns referenced by the table's
- indexes, including expression and partial indexes.
+ The update only modifies columns which are not referenced by the
+ table's indexes or are only referenced by summarizing indexes (such
+ as <acronym>BRIN</acronym>) and does not update any columns
+ referenced by the table's non-summarizing indexes, including
+ expression and partial non-summarizing indexes.
</para>
</listitem>
<listitem>
@@ -1114,7 +1117,8 @@ data. Empty in ordinary tables.</entry>
<itemizedlist>
<listitem>
<para>
- New index entries are not needed to represent updated rows.
+ New index entries are not needed to represent updated rows, however,
+ summary indexes may still need to be updated.
</para>
</listitem>
<listitem>
@@ -1130,11 +1134,10 @@ data. Empty in ordinary tables.</entry>
</para>
<para>
- In summary, heap-only tuple updates can only be created
- if columns used by indexes are not updated. You can
- increase the likelihood of sufficient page space for
- <acronym>HOT</acronym> updates by decreasing a table's <link
- linkend="reloption-fillfactor"><literal>fillfactor</literal></link>.
+ In summary, heap-only tuple updates can only be created if columns used by
+ non-summarizing indexes are not updated. You can increase the likelihood of
+ sufficient page space for <acronym>HOT</acronym> updates by decreasing
+ a table's <link linkend="reloption-fillfactor"><literal>fillfactor</literal></link>.
If you don't, <acronym>HOT</acronym> updates will still happen because
new rows will naturally migrate to new pages and existing pages with
sufficient free space for new row versions. The system view <link
--
2.34.1
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