Re: [PATCHES] odd output in restore mode

Simon Riggs wrote:
> On Tue, 2008-07-22 at 17:19 -0700, Martin Zaun wrote:
>> 8. Unresolved question of implementing now/later a "cp" replacement
>
> The patch implements what's been agreed.
>
> I'm not rewriting "cp", for reasons already discussed.
>
> Not a comment to you Martin, but it's fairly clear that I'm not
> maintaining this correctly for Windows. I've never claimed to have
> tested this on Windows, and only included Windows related items as
> requested by others. I need to make it clear that I'm not going to
> maintain it at all, for Windows. If others wish to report Windows issues
> then they can suggest appropriate fixes and test them also.

Hmm. I just realized that replacing the "cp" command within pg_standby
won't help at all. The problem is with the command that copies the files
*to* the archivelocation that pg_standby polls, not with the copy
pg_standby does from archivelocation to pg_xlog. And we don't have much
control over that.

We really need a more reliable way of detecting that a file has been
fully copied. One simple improvement would be to check the xlp_magic
field of the last page, though it still wouldn't be bullet-proof.

Do the commands that preallocate the space keep the file exclusively
locked during the copy? If they do, shouldn't we get an error in trying
to run the restore copy command, and retry after the 1s sleep in
RestoreWALFileForRecovery? Though if the archive location is a samba
mount or something, I guess we can't rely on Windows-style exclusive
locking.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com