| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Alexey Kondratov <kondratov(dot)aleksey(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Peter Geoghegan <pg(at)bowt(dot)ie>, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru>, Robert Haas <robertmhaas(at)gmail(dot)com>, Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Anastasia Lubennikova <lubennikovaAV(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] GSOC'17 project introduction: Parallel COPY execution with errors handling |
| Date: | 2018-03-03 14:30:02 |
| Message-ID: | CAFj8pRA4pznAjyT44xxv-ryiVzao5DJvUHh9kXBSCWYGQ9w_MQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
2018-03-03 15:02 GMT+01:00 Peter Eisentraut <
peter(dot)eisentraut(at)2ndquadrant(dot)com>:
> On 3/3/18 00:48, Tom Lane wrote:
> > I don't think that can possibly work. It would only be safe if, between
> > the thrower and the catcher, there were no other levels of control
> > operating according to the normal error-handling rules. But input
> > functions certainly cannot assume that they are only called by COPY,
> > so how could they safely throw a "soft error"?
>
> That assumes that throwing a soft error in a context that does not
> handle it specially is not safe. I'd imagine in such situations the
> soft error just behaves like a normal exception.
>
This soft error solves what? If somebody use fault tolerant COPY, then he
will not be satisfied, when only format errors will be ignored. Any
constraints, maybe trigger errors should be ignored too.
But is true, so some other databases raises soft error on format issues,
and doesn't raise a exception. Isn't better to use some alternative
algorithm like
under subtransaction try to insert block of 1000 lines. When some fails do
rollback and try to import per block of 100 lines, and try to find wrong
line?
or another way - for this specific case reduce the cost of subtransaction?
This is special case, subtransaction under one command.
Regards
Pavel
>
> --
> Peter Eisentraut http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
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