Re: Location for pgstat.stat

Tom Lane wrote:
> Magnus Hagander <magnus(at)hagander(dot)net> writes:
>> Tom Lane wrote:
>>> It doesn't seem to me that it'd be hard to support two locations for the
>>> stats file --- it'd just take another parameter to the read and write
>>> routines. pgstat.c already knows the difference between a normal write
>>> and a shutdown write ...
>
>> Right. Should it be removed from the permanent location when the server
>> starts?
>
> Yes, I would say so. There are two possible exit paths: normal shutdown
> (where we'd write a new file) and crash. In a crash we'd wish to delete
> the file anyway for fear that it's corrupted.
>
> Startup: read permanent file, then delete it.
>
> Post-crash: remove any permanent file (same as now)
>
> Shutdown: write permanent file.
>
> Normal stats collector write: write temp file.
>
> Backend stats fetch: read temp file.

Attached is a patch that implements this. I went with the option of just
storing it in a temporary directory that can be symlinked, and not
bothering with a GUC for it. Comments? (documentation updates are also
needed, but I'll wait with those until I hear patch comments :-P)

//Magnus