Re: Add on_error and log_verbosity options to file_fdw

On 2024-07-05 00:27, torikoshia wrote:
> Hi,
>
> With the current file_fdw, if even one line of data conversion fails,
> the contents of the file cannot be referenced at all:
>
> =# \! cat data/test.data
> 1,a
> 2,b
> a,c
> =# create foreign table f_fdw_test_1 (i int, t text) server f_fdw
> options (filename 'test.data', format 'csv');
> CREATE FOREIGN TABLE
>
> =# table f_fdw_test_1;
> ERROR: invalid input syntax for type integer: "a"
> CONTEXT: COPY f_fdw_test, line 3, column i: "a"
>
> Since we'll support ON_ERROR option which tolerates data conversion
> errors in COPY FROM and LOG_VERBOSITY option at v17[1], how about
> supporting them on file_fdw?
>
> This idea comes from Fujii-san[2], and I think it'd be useful when
> reading a bit dirty data.
>
> Attached PoC patch works like below:
>
> =# create foreign table f_fdw_test_2 (i int, t text) server f_fdw
> options (filename 'test.data', format 'csv', on_error 'ignore');
> CREATE FOREIGN TABLE
>
> =# table f_fdw_test_2;
> NOTICE: 1 row was skipped due to data type incompatibility
> i | t
> ---+---
> 1 | a
> 2 | b
> (2 rows)
>
>
> =# create foreign table f_fdw_test_3 (i int, t text) server f_fdw
> options (filename 'test.data', format 'csv', on_error 'ignore',
> log_verbosity 'verbose');
> CREATE FOREIGN TABLE
>
> =# table f_fdw_test_3 ;
> NOTICE: skipping row due to data type incompatibility at line 3 for
> column i: "a"
> NOTICE: 1 row was skipped due to data type incompatibility
> i | t
> ---+---
> 1 | a
> 2 | b
> (2 rows)
>
>
> I'm going to continue developing the patch(e.g. add doc, measure
> performance degradation) when people also think this feature is worth
> adding.
>
>
> What do you think?
>
>
> [1] https://www.postgresql.org/docs/devel/sql-copy.html
> [2] https://x.com/fujii_masao/status/1808178032219509041

Update the patch since v1 patch caused compiler warning.

--
Regards,

--
Atsushi Torikoshi
NTT DATA Group Corporation