Re: In which case PG_VERSION file updates ?

>
> From what I can see, PG_VERSION is written at database creation to document
> the
> major version of the Postgres instance used to create the database. Since
> it
> only holds the major version string (i.e. 9.0) it is not touched during
> minor
> updates, for example 9.0.0 --> 9.0.1. Grepping the pg_upgrade code shows
> it
> might touch PG_VERSION. A quick grep on the rest of the source code shows
> only
> initdb writing out PG_VERSION, though it is checked by other code. This is
> by no
> means an in depth look and it would take some one with more knowledge of
> Postgres internals to give you a definitive answer. Might be worth a post
> on -
> hackers.

Thank you Adrian Klaver / Scott Marlowe for your valuable inputs. I got
clarified.

As said, PG_VERSION file is created at the time of Database creation.
Sometimes, question arises that at what time database created. For this we
don't have any information to get from pg_catalogs, so with PG_VERSION file
timestamp we can pull database creation time.

However, with your inputs its clear that when PG_VERSION file is touched. In
pg_upgrade or any of the Postgres Internals touching PG_VERSION file will
never get exact database creation time.

I am not knowing why database creation time is not considered to be in
pg_catalogs.

-- Raghav