Re: COPY enhancements

On Thu, 2009-10-08 at 11:59 -0400, Robert Haas wrote:
> On Thu, Oct 8, 2009 at 11:50 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> Another possible approach, which isn't perfect either, is the idea of
> >> allowing COPY to generate a single column of output of type text[].
> >> That greatly reduces the number of possible error cases, and at least
> >> gets the data into the DB where you can hack on it.  But it's still
> >> going to be painful for some use cases.
> >
> > Yeah, that connects to the previous discussion about refactoring COPY
> > into a series of steps that the user can control.
> >
> > Ultimately, there's always going to be a tradeoff between speed and
> > flexibility.  It may be that we should just say "if you want to import
> > dirty data, it's gonna cost ya" and not worry about the speed penalty
> > of subtransaction-per-row.  But that still leaves us with the 2^32
> > limit.  I wonder whether we could break down COPY into sub-sub
> > transactions to work around that...
>
> How would that work?  Don't you still need to increment the command counter?

Couldn't you just commit each range of subtransactions based on some
threshold?

COPY foo from '/tmp/bar/' COMMIT_THRESHOLD 1000000;

It counts to 1mil, commits starts a new transaction. Yes there would be
1million sub transactions but once it hits those clean, it commits.

?

Joshua D. Drake


>
> ...Robert
>
--
PostgreSQL.org Major Contributor
Command Prompt, Inc: http://www.commandprompt.com/ - 503.667.4564
Consulting, Training, Support, Custom Development, Engineering
If the world pushes look it in the eye and GRR. Then push back harder. - Salamander