Re: Change COPY ... ON_ERROR ignore to ON_ERROR ignore_row

On 22/01/26 11:45, jian he wrote:
>> Should FORCE_NOT_NULL be allowed to be used with ON_ERROR set_null? It
>> seems to me that ON_ERROR set_null overwrite the FORCE_NOT_NULL
>> behaviour:
>>
>> postgres=# create table t4(a int, b varchar(5));
>> CREATE TABLE
>>
>> postgres=# copy t4 from 'data.csv' with (FORCE_NOT_NULL(b), format csv, delimiter ',', NULL 'NULL', ON_ERROR set_null);
>> NOTICE: invalid values in 2 rows were replaced with null due to data type incompatibility
>> COPY 5
>>
>> postgres=# \pset null 'NULL'
>> Null display is "NULL".
>> postgres=# select * from t4;
>> a | b
>> ---+------
>> 1 | aaaa
>> 2 | bbbb
>> 2 | NULL
>> 2 | NULL
>> 5 | NULL
>> (5 rows)
>>
>> Note that only the ccccc rows on .csv file was inserted with a NULL
>> value on b column. The 5,NULL row was inserted with a "NULL" string as a
>> value:
>>
>> postgres=# select * from t4 where b is null;
>> a | b
>> ---+------
>> 2 | NULL
>> 2 | NULL
>> (2 rows)
>>
>> The contents of data.csv:
>> 1,aaaa
>> 2,bbbb
>> 2,ccccc
>> 2,ccccc
>> 5,NULL
>>
>> Perhaps we should block the usage of FORCE_NOT_NULL with ON_ERROR
>> SET_NULL?
>>
> FORCE_NOT_NULL is related to how we handle NULL string in column value.
>
> We first process cstate->opts.force_notnull_flags, cstate->opts.force_null_flags
> then InputFunctionCallSafe.
> see copyfromparse.c, CopyFromTextLikeOneRow ``if (is_csv)``loop.
>
> I think these two are unrelated things, FORCE_NOT_NULL should be fine with
> ON_ERROR SET_NULL.
> you can see related tests in
> https://git.postgresql.org/cgit/postgresql.git/tree/src/test/regress/sql/copy2.sql#n330
>
> Am I missing something?

Yeah, after some more thinking it seems ok to use both options
together. I just found a bit strange when using integer columns.
Consider this example:

cat data.csv
1,11
2,22
3,
4,44

postgres=# create table t(a int not null, b int);
CREATE TABLE

postgres=# copy t from
'/Users/matheus/dev/pgdev/copy-on-error-set-null/data.csv' with
(FORCE_NOT_NULL(b), format csv, delimiter ',', ON_ERROR set_null);
NOTICE: 1 row was replaced with null due to data type incompatibility
COPY 4

postgres=# select * from t where b is null;
a | b
---+---
3 |
(1 row)

We are requiring a not null value on column b but we are still
generating rows with null values on b.

The reasoning on this is that the row 3 would generate a "invalid
input syntax for type integer" error and the ON_ERROR set_null fix
this by inserting a NULL value. It make sense I think but I'm
wondering if it could cause any confusion?

>> On monitoring.sgml we have the following for pg_stat_progress_copy
>> tuples_skipped:
>> Number of tuples skipped because they contain malformed data.
>> This counter only advances when a value other than
>> <literal>stop</literal> is specified to the <literal>ON_ERROR</literal>
>>
>> IIUC we are not updating this view if we set a column to NULL due to an
>> error, perhaps this documentation should be updated to mention that it
>> will not be updated with ON_ERROR set_null?
>>
>
> IMHO, we don't need to mention ON_ERROR set_null, since we do not support it.
> change to the following should be ok, i think.
>
> <para>
> Number of tuples skipped because they contain malformed data.
> This counter only advances when
> <literal>ignore</literal> is specified to the <literal>ON_ERROR</literal>
> option.
> </para></entry>

It looks good, I was thinking in something like this.

>>
>> I may have missing something, but we are still considering implementing
>> the REJECT_LIMIT + ON_ERROR set_null?
> Possibly as a separate patch later.
Ok, good, thanks.

--
Matheus Alcantara
EDB: https://www.enterprisedb.com