On Thu, Jan 7, 2021 at 3:05 PM Daniel Gustafsson <dan...@yesql.se> wrote: > > > On 5 Jan 2021, at 18:19, Michael Banck <michael.ba...@credativ.de> wrote: > > >> diff --git a/doc/src/sgml/ref/initdb.sgml b/doc/src/sgml/ref/initdb.sgml > >> index 385ac25150..e3b0048806 100644 > >> --- a/doc/src/sgml/ref/initdb.sgml > >> +++ b/doc/src/sgml/ref/initdb.sgml > >> @@ -219,6 +219,7 @@ PostgreSQL documentation > >> failures will be reported in the > >> <link linkend="monitoring-pg-stat-database-view"> > >> <structname>pg_stat_database</structname></link> view. > >> + See <xref linkend="checksums" /> for details. > >> </para> > >> </listitem> > >> </varlistentry> > > > >> diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml > >> index f4bc147b10..5dcfcdd2ff 100644 > >> --- a/doc/src/sgml/wal.sgml > >> +++ b/doc/src/sgml/wal.sgml > >> @@ -230,6 +230,103 @@ > >> </para> > >> </sect1> > >> > >> + <sect1 id="checksums"> > >> + <title>Data Checksums</title> > >> + <indexterm> > >> + <primary>checksums</primary> > >> + </indexterm> > >> + > >> + <para> > >> + Data pages are not checksum protected by default, but this can > >> optionally be > >> + enabled for a cluster. When enabled, each data page will be assigned a > >> + checksum that is updated when the page is written and verified every > >> time > >> + the page is read. Only data pages are protected by checksums, internal > >> data > >> + structures and temporary files are not. > >> + </para> > >> + > >> + <para> > >> + Checksums are normally enabled when the cluster is initialized using > >> <link > >> + > >> linkend="app-initdb-data-checksums"><application>initdb</application></link>. > >> + They can also be enabled or disabled at a later time, either as an > >> offline > >> + operation or in a running cluster. In all cases, checksums are enabled > >> or > >> + disabled at the full cluster level, and cannot be specified > >> individually for > >> + databases or tables. > >> + </para> > >> + > >> + <para> > >> + The current state of checksums in the cluster can be verified by > >> viewing the > >> + value of the read-only configuration variable <xref > >> + linkend="guc-data-checksums" /> by issuing the command <command>SHOW > >> + data_checksums</command>. > >> + </para> > >> + > >> + <para> > >> + When attempting to recover from corrupt data it may be necessary to > >> bypass > >> + the checksum protection in order to recover data. To do this, > >> temporarily > >> + set the configuration parameter <xref > >> linkend="guc-ignore-checksum-failure" />. > >> + </para> > > > > I think the above is rather informative about checksums in general and > > not specific to online activation of checksusm, so could pretty much be > > committed verbatim right now, except for the "either as an offline > > operation or in a running cluster" bit which would have to be rewritten. > > That might indeedbe useful regardless of the state of this patch. Robert and > Heikki: being committers who have both reviewed recent versions of the patch, > would you prefer these sections be broken out into a separate patch?
I think it would be ;) Obviously in that case adapted so that it has to be changed offline, and the patch would have to change that to say it can be changed online. -- Magnus Hagander Me: https://www.hagander.net/ Work: https://www.redpill-linpro.com/
