Re: [PATCHES] Forcing current WAL file to be archived - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: [PATCHES] Forcing current WAL file to be archived
Date
Msg-id 200608140243.k7E2ho000108@momjian.us
Whole thread Raw
In response to Re: [PATCHES] Forcing current WAL file to be archived  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: [PATCHES] Forcing current WAL file to be archived
List pgsql-hackers
This issue is closed, right?

---------------------------------------------------------------------------

Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > Something Hannu wrote has just reminded me that
> > pg_current_xlog_location() returns the current Insert pointer rather
> > than the current Write pointer.
> > That would not be useful for streaming xlog records would it?
>
> Good point.
>
> > Methinks it should be the Write pointer all of the time, since I can't
> > think of a valid reason for wanting to know where the Insert pointer is
> > *before* we've written to the xlog file. Having it be the Insert pointer
> > could lead to some errors.
>
> However the start/stop_backup functions return the Insert pointer.
> I can see scripts getting confused if pg_current_xlog_location reports
> something less than what they just got from pg_stop_backup.
>
> Is there value in exposing both pointers?  (Maybe not, it'll just cause
> confusion probably.)
>
> Another option is to have pg_current_xlog_location force a write (but
> not fsync) as far as the Insert pointer it's about to return.  This
> would eliminate any issues about inconsistency between results, but
> perhaps there's too much performance penalty.
>
> I'm not necessarily against your suggestion, just trying to be sure
> we've thought about all the options.
>
>             regards, tom lane

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  Bruce Momjian   bruce@momjian.us
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