Re: Add new COPY option REJECT_LIMIT - Mailing list pgsql-hackers

On 2024-07-05 12:59, Fujii Masao wrote:
> On 2024/07/04 12:05, torikoshia wrote:
>> I'm going to update it after discussing the option format as described 
>> below.
> 
> Thanks!
> 
>> I agree that it's possible to use only REJECT_LIMIT without ON_ERROR.
>> I also think it's easy to understand that REJECT_LIMIT=0 is 
>> ON_ERROR=stop.
>> However, expressing REJECT_LIMIT='infinity' needs some definition like 
>> "setting REJECT_LIMIT to -1 means 'infinity'", doesn't it? If so, I 
>> think this might not so intuitive.
> 
> How about allowing REJECT_LIMIT to accept the keywords "infinity", 
> "unlimited",
> or "all" in addition to a number? This way, users can specify one of 
> these
> keywords instead of -1 to ignore all errors. The server code would then
> internally set the REJECT_LIMIT to -1 or another appropriate value when
> these keywords are used, but users wouldn't need to worry about this 
> detail.

Agreed.

> If we choose "all" as the keyword, renaming the option to IGNORE_ERRORS
> might be more intuitive and easier to understand than REJECT_LIMIT.

I feel that 'infinite' and 'unlimited' are unfamiliar values for 
PostgreSQL parameters, so 'all' might be better and IGNORE_ERRORS would 
be a better parameter name as your suggestion.

>> Also, since it seems Snowflake and Redshift have both options 
>> equivalent to REJECT_LIMIT and ON_ERROR, having both of them in 
>> PostgreSQL COPY might not be surprising:
>> - Snowflake's ON_ERROR accepts "CONTINUE | SKIP_FILE | SKIP_FILE_num | 
>> 'SKIP_FILE_num%' | ABORT_STATEMENT"[1]
>> - Redshift has MAXERROR and IGNOREALLERRORS options[2]
> 
> Ok, so here's a summary of the options and their behaviors:
> 
> To ignore all errors and continue to the end:
> 
> - Snowflake: ON_ERROR=CONTINUE
> - Redshift: IGNOREALLERRORS
> - Postgres (with your patch): ON_ERROR=ignore
> - Postgres (with my idea): IGNORE_ERRORS=all
> 
> To fail as soon as an error is found:
> 
> - Snowflake: ON_ERROR=ABORT_STATEMENT (default) / SKIP_FILE
> - Redshift: MAXERROR=0 (default)
> - Postgres (with your patch): ON_ERROR=stop (default)
> - Postgres (with my idea): IGNORE_ERRORS=0 (default)
> 
> To fail when NNN or more errors are found:
> 
> - Snowflake: ON_ERROR=SKIP_FILE_NNN
> - Redshift: MAXERROR=NNN
> - Postgres (with your patch): REJECT_LIMIT=NNN-1 and ON_ERROR=ignore
> - Postgres (with my idea): IGNORE_ERRORS=NNN

Thanks for the summary.

> This makes me think it might be better to treat REJECT_LIMIT as
> an additional option for ON_ERROR=stop instead of ON_ERROR=ignore
> if we adopt your patch. Since ON_ERROR=stop is the default,
> users could set the maximum number of allowed errors by specifying
> only REJECT_LIMIT. Otherwise, they would need to specify both
> ON_ERROR=ignore and REJECT_LIMIT.

That makes sense.

-- 
Regards,

--
Atsushi Torikoshi
NTT DATA Group Corporation