Re: POC PATCH: copy from ... exceptions to: (was Re: VLDB Features) - Mailing list pgsql-hackers

On Thu, Mar 28, 2024 at 9:38 PM torikoshia <torikoshia@oss.nttdata.com> wrote:
>
> On 2024-03-28 10:20, Masahiko Sawada wrote:
> > Hi,
> >
> > On Thu, Jan 18, 2024 at 5:33 PM Masahiko Sawada <sawada.mshk@gmail.com>
> > wrote:
> >>
> >> On Thu, Jan 18, 2024 at 4:59 PM Alexander Korotkov
> >> <aekorotkov@gmail.com> wrote:
> >> >
> >> > On Thu, Jan 18, 2024 at 4:16 AM torikoshia <torikoshia@oss.nttdata.com> wrote:
> >> > > On 2024-01-18 10:10, jian he wrote:
> >> > > > On Thu, Jan 18, 2024 at 8:57 AM Masahiko Sawada <sawada.mshk@gmail.com>
> >> > > > wrote:
> >> > > >> On Thu, Jan 18, 2024 at 6:38 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> > > >> > Kyotaro-san's suggestion isn't bad, though I might shorten it to
> >> > > >> > error_action {error|ignore|log} (or perhaps "stop" instead of "error")?
> >> > > >> > You will need a separate parameter anyway to specify the destination
> >> > > >> > of "log", unless "none" became an illegal table name when I wasn't
> >> > > >> > looking.  I don't buy that one parameter that has some special values
> >> > > >> > while other values could be names will be a good design.  Moreover,
> >> > > >> > what if we want to support (say) log-to-file along with log-to-table?
> >> > > >> > Trying to distinguish a file name from a table name without any other
> >> > > >> > context seems impossible.
> >> > > >>
> >> > > >> I've been thinking we can add more values to this option to log errors
> >> > > >> not only to the server logs but also to the error table (not sure
> >> > > >> details but I imagined an error table is created for each table on
> >> > > >> error), without an additional option for the destination name. The
> >> > > >> values would be like error_action {error|ignore|save-logs|save-table}.
> >> > > >>
> >> > > >
> >> > > > another idea:
> >> > > > on_error {error|ignore|other_future_option}
> >> > > > if not specified then by default ERROR.
> >> > > > You can also specify ERROR or IGNORE for now.
> >> > > >
> >> > > > I agree, the parameter "error_action" is better than "location".
> >> > >
> >> > > I'm not sure whether error_action or on_error is better, but either way
> >> > > "error_action error" and "on_error error" seems a bit odd to me.
> >> > > I feel "stop" is better for both cases as Tom suggested.
> >> >
> >> > OK.  What about this?
> >> > on_error {stop|ignore|other_future_option}
> >> > where other_future_option might be compound like "file 'copy.log'" or
> >> > "table 'copy_log'".
> >>
> >> +1
> >>
> >
> > I realized that ON_ERROR syntax synoposis in the documentation is not
> > correct. The option doesn't require the value to be quoted and the
> > value can be omitted. The attached patch fixes it.
> >
> > Regards,
>
> Thanks!
>
> Attached patch fixes the doc, but I'm wondering perhaps it might be
> better to modify the codes to prohibit abbreviation of the value.
>
> When seeing the query which abbreviates ON_ERROR value, I feel it's not
> obvious what happens compared to other options which tolerates
> abbreviation of the value such as FREEZE or HEADER.
>
>    COPY t1 FROM stdin WITH (ON_ERROR);
>
> What do you think?

Indeed. Looking at options of other commands such as VACUUM and
EXPLAIN, I can see that we can omit a boolean value, but non-boolean
parameters require its value. The HEADER option is not a pure boolean
parameter but we can omit the value. It seems to be for backward
compatibility; it used to be a boolean parameter. I agree that the
above example would confuse users.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com