Jeff Janes wrote:
> On Tue, Jan 25, 2011 at 5:32 PM, Bruce Momjian <bruce@xxxxxxxxxx> wrote:
> > Robert Haas wrote:
> >> On Wed, Jan 19, 2011 at 12:07 PM, Bruce Momjian <bruce@xxxxxxxxxx> wrote:
>
> >> > ? ? ? ?http://developer.postgresql.org/pgdocs/postgres/non-durability.html
> >>
> >> This sentence looks to me like it should be removed, or perhaps clarified:
> >>
> >> ? ? This does affect database crash transaction durability.
> >
> > Uh, doesn't it affect database crash transaction durability? ?I have
> > applied the attached patch to clarify things. ?Thanks.
>
> I think the point that was trying to be made there was that the other
> parameters only lose and corrupt data when the machine crashes.
> Synchronous commit turned off will lose data on a mere postgresql
> server crash, it doesn't require a machine-level crash to cause data
> loss.
>
> Indeed, the currently committed doc is quite misleading.
>
> " The following are configuration changes you can make
> to improve performance in such cases; they do not invalidate
> commit guarantees related to database crashes, only abrupt operating
> system stoppage, except as mentioned below"
>
> We've now removed the thing being mentioned below, but did not remove
> the promise we would be mentioning those things.
Excellent point. The old wording was just too clever and even I forgot
why I was making that point. I have updated the docs to clearly state
why this setting is different from the ones above. Thanks for spotting
this.
Applied patch attached.
--
Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 0a10457..1bec5b1 100644
*** a/doc/src/sgml/perform.sgml
--- b/doc/src/sgml/perform.sgml
*************** SELECT * FROM x, y, a, b, c WHERE someth
*** 1157,1165 ****
<listitem>
<para>
! Turn off <xref linkend="guc-synchronous-commit">; there is no
need to write the <acronym>WAL</acronym> to disk on every
! commit.
</para>
</listitem>
</itemizedlist>
--- 1157,1166 ----
<listitem>
<para>
! Turn off <xref linkend="guc-synchronous-commit">; there might be no
need to write the <acronym>WAL</acronym> to disk on every
! commit. This does enable possible tranaction loss in case of
! a <emphasis>database</> crash.
</para>
</listitem>
</itemizedlist>
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