Jeff Janes <> wrote:

> But I do wonder what experience people have with the 3 stage
> process, how useful is it empirically?  If you can't open the
> database for general use until the 3rd phase is done, then you
> would just jump to doing that stage, rather than working through
> all 3 of them.  If you can open the database and muddle through
> without statistics for a while, why not muddle through for the
> little bit longer that it would take to collect the full set
> right off the bat, rather than making intermediate passes?

It's not always a "little bit" of time.  For a description of my
experience with a home-grown 3 stage process before one was built
into pg_upgrade, see this post:

Basically, we cut our down time from hours to minutes without
serious impairment of performance.

Kevin Grittner
The Enterprise PostgreSQL Company

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