Re: File-per-GUC WAS: Re: ALTER SYSTEM SET command to change postgresql.conf parameters (RE: Proposal for Allow postgresql.conf values to be changed via SQL [review])

Josh Berkus wrote
> (this discussion concerns issue (D), file-per-setting vs. one-big-file)
> 
> So the case of two sessions both modifying ALTER SYSTEM SET, and one
> succeeding for some-but-all-GUCS, and the other succeeding for
> some-but-not-all-GUCs, would not be user-friendly or pretty, even if
> each setting change succeeded or failed atomically.

Can the final file write occur only at "COMMIT;" with anything inside a
transaction simply staged up for later saving (or rollback).  The file write
phase as a whole then needs to be atomic and not just a single GUC-file.

Could the system read the last update timestamp of each GUC-file when the
original statement is executed and then re-read all of them at commit and
fail with some kind of serialization error if the last-update timestamp on
any of the files has changed?

I dislike the idea of any kind of automatic reload.  That said some kind of
"have their been any configuration changes since last reload?"
query/function makes sense.  In can be plugged into Nagios or similar to
warn if these changes are occurring but made live.

David J.




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