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From: David G. Johnston <[email protected]>
To: jian he <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Change COPY ... ON_ERROR ignore to ON_ERROR ignore_row
Date: Sun, 28 Jan 2024 17:19:47 -0700
Message-ID: <CAKFQuwaTbpvRtvmewXjL-V08CLy5=HSL6ehccAZgSGVkcH-WXg@mail.gmail.com> (raw)
In-Reply-To: <CACJufxExhY9P8a-rk21wR2NXF-UydMjictyiKiMMi_Z4iX6gNQ@mail.gmail.com>
References: <CAKFQuwawy1e6YR4S=j+y7pXqg_Dw1WBVrgvf=BP3d1_aSfe_+Q@mail.gmail.com>
	<CACJufxExhY9P8a-rk21wR2NXF-UydMjictyiKiMMi_Z4iX6gNQ@mail.gmail.com>

On Sun, Jan 28, 2024 at 4:51 PM jian he <[email protected]> wrote:

> On Fri, Jan 26, 2024 at 11:09 PM David G. Johnston
> <[email protected]> wrote:
> >
> > Hi,
> >
> > The option choice of "ignore" in the COPY ON_ERROR clause seems overly
> generic.  There would seem to be two relevant ways to ignore bad column
> input data - drop the entire row or just set the column value to null.  I
> can see us wanting to provide the set to null option and in any case having
> the option name be explicit that it ignores the row seems like a good idea.
>
> two issue I found out while playing around with it;
> create table x1(a int not null, b int not null );
>
> another issue:
> COPY x1 from stdin (on_error null);
>
> when we already have `not null` top level constraint for table x1.
> Do we need an error immediately?
> "on_error null" seems to conflict with `not null` constraint (assume
> refers to the same column).
> it may fail while doing bulk inserts while on_error is set to null
> because of violating a not null constraint.
>

You should not error immediately since whether or not there is a problem is
table and data dependent.  I would not check for the case of all columns
being defined not null and just let the mismatch happen.

That said, maybe with this being a string we can accept something like:
'null, ignore'

And so if attempting to place any one null fails, assuming we can make that
a soft error too, we would then ignore the entire row.

David J.

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