Re: [HACKERS] GSoC 2017: Foreign Key Arrays

According to the last review, there are still two main issues with the
patch.

On Mon, Oct 30, 2017 at 3:24 AM, Andreas Karlsson <andreas(at)proxel(dot)se> wrote:

> 1) MATCH FULL does not seem to care about NULLS in arrays. In the example
> below I expected both inserts into the referring table to fail.
>
> CREATE TABLE t (x int, y int, PRIMARY KEY (x, y));
> CREATE TABLE fk (x int, ys int[], FOREIGN KEY (x, EACH ELEMENT OF ys)
> REFERENCES t MATCH FULL);
> INSERT INTO t VALUES (10, 1);
> INSERT INTO fk VALUES (10, '{1,NULL}');
> INSERT INTO fk VALUES (NULL, '{1}');
>
> CREATE TABLE
> CREATE TABLE
> INSERT 0 1
> INSERT 0 1
> ERROR: insert or update on table "fk" violates foreign key constraint
> "fk_x_fkey"
> DETAIL: MATCH FULL does not allow mixing of null and nonnull key values.
>
> I understand that Match full should contain nulls in the results. However,
I don't think that it's semantically correct, so I suggest we don't use
Match full. What would be the consequences of that ?

2) I think the code in RI_Initial_Check() would be cleaner if you used
> "CROSS JOIN LATERAL unnest(col)" rather than having unnest() in the target
> list. This way you would not need to rename all columns and the code paths
> for the array case could look more like the code path for the normal case.
>
I have repeatedly tried to generate the suggested query using C code and I
failed. I would like some help with it

Best Regards,
Mark Rofail