Re: Regression in COPY FROM caused by 9f8377f7a2

On Mon, 2023-09-25 at 09:54 +0200, Laurenz Albe wrote:
> In v16 and later, the following fails:
>
> CREATE TABLE boom (t character varying(5) DEFAULT 'a long string');
>
> COPY boom FROM STDIN;
> ERROR:  value too long for type character varying(5)
>
> In PostgreSQL v15 and earlier, the COPY statement succeeds.
>
> The error is thrown in BeginCopyFrom in line 1578 (HEAD)
>
>   defexpr = expression_planner(defexpr);
>
> Bisecting shows that the regression was introduced by commit 9f8377f7a2,
> which introduced DEFAULT values for COPY FROM.

I suggest the attached fix, which evaluates default values only if
the DEFAULT option was specified or if the column does not appear in
the column list of COPY.

Yours,
Laurenz Albe