Re: TRUNCATE+COPY optimization and --jobs=1 in pg_restore

Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> Tom Lane wrote:
>> The code is only trying to substitute for something you can't have
>> in parallel restore, ie --single-transaction.

> Exactly. IIRC that's why --single-transaction was introduced in the
> first place.

To me, --single-transaction is mostly there for people who want to be
sure they have all-or-nothing restore behavior. Optimizations are
secondary.

> Takahiro-san is suggesting there is a case for doing the optimisation in
> non-parallel mode. But if we do that, is there still a case for
> --single-transaction?

Yeah, per above. The main problem I have with doing it in non-parallel
restore mode is that we couldn't safely do it when outputting to a
script (since we don't know if the user will try to put begin/end
around the script), and I really do not want to allow any differences
between script output and direct-to-database output. Once that camel's
nose gets under the tent, debuggability will go down the tubes...

regards, tom lane