Alvaro Herrera wrote: > Excerpts from Tom Lane's message of lun ago 23 12:40:32 -0400 2010: > > Alvaro Herrera <alvhe...@commandprompt.com> writes: > > > Excerpts from Bruce Momjian's message of dom ago 22 12:51:47 -0400 2010: > > >> Do you have a suggestion? Reorder the items? > > > > > I'd add another para before that one saying that this value "also" > > > affects pg_clog truncation. I agree that putting pg_clog truncation as > > > the first item here is not an improvement. For most people, having > > > those pg_clog files there or not is going to be a wash, compared to data > > > size. > > > > I was going to suggest that the point about pg_clog should be in a > > separate paragraph *after* this one, since it seems like a secondary > > issue. But anyway, I agree with putting this para back as it was and > > talking about clog in a separate para. > > Sorry, yes, I was also thinking "after". I don't know what made me > write "before" but it wasn't clarity of thought.
OK, I have attached a proposed patch to improve this. I moved the pg_clog mention to a new paragraph and linked it to the reason the default is relatively low. Comments? -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +
Index: doc/src/sgml/config.sgml =================================================================== RCS file: /cvsroot/pgsql/doc/src/sgml/config.sgml,v retrieving revision 1.307 diff -c -c -r1.307 config.sgml *** doc/src/sgml/config.sgml 23 Aug 2010 02:43:25 -0000 1.307 --- doc/src/sgml/config.sgml 23 Aug 2010 18:55:02 -0000 *************** *** 4150,4161 **** <para> Specifies the maximum age (in transactions) that a table's <structname>pg_class</>.<structfield>relfrozenxid</> field can ! attain before a <command>VACUUM</> operation is forced to allow removal ! of old files from the <filename>pg_clog</> subdirectory and prevent ! transaction ID wraparound within the table. Note that the system ! will launch autovacuum processes to prevent wraparound even when ! autovacuum is otherwise disabled. ! The default is 200 million transactions. This parameter can only be set at server start, but the setting can be reduced for individual tables by changing storage parameters. --- 4150,4165 ---- <para> Specifies the maximum age (in transactions) that a table's <structname>pg_class</>.<structfield>relfrozenxid</> field can ! attain before a <command>VACUUM</> freeze operation is forced ! to prevent transaction ID wraparound within the table. ! Note that the system will launch autovacuum processes to ! prevent wraparound even when autovacuum is otherwise disabled. ! </para> ! ! <para> ! Vacuum freeze also allows removal of old files from the ! <filename>pg_clog</> subdirectory, which is why the default ! is a relatively low 200 million transactions. This parameter can only be set at server start, but the setting can be reduced for individual tables by changing storage parameters.
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