Re: For the ametures. (related to "Are we losing momentum?")

Ben Clewett writes:

> I could not work out from the documentation whether it takes a snapshot
> at the start time, or archives data at the time it find's it. The
> documentation (app-pg-dump.html). As the documentation does not clarify
> this very important point, I desided it's not safe to use when the
> system is in use.
>
> Can this command can be used, with users in the system making heavy
> changes, and when takes many hours to complete, does produce a valid and
> consistent backup?

From the pg_dump reference page:

<para>
<application>pg_dump</application> makes consistent backups even if the
database is being used concurrently. <application>pg_dump</application>
does not block other users accessing the database (readers or
writers).
</para>

From the chapter Backup and Restore:

<para>
Dumps created by <application>pg_dump</> are internally consistent,
that is, updates to the database while <application>pg_dump</> is
running will not be in the dump. <application>pg_dump</> does not
block other operations on the database while it is working.
(Exceptions are those operations that need to operate with an
exclusive lock, such as <command>VACUUM FULL</command>.)
</para>

--
Peter Eisentraut peter_e(at)gmx(dot)net