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

On 2024-03-28 21:54, Masahiko Sawada wrote:
> 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,

Thanks for your comment!

Attached a patch which modifies the code to prohibit omission of its 
value.

I was a little unsure about adding a regression test for this, but I 
have not added it since other COPY option doesn't test the omission of 
its value.

-- 
Regards,

--
Atsushi Torikoshi
NTT DATA Group Corporation