Re: [HACKERS] GSoC 2017: Foreign Key Arrays

Greetings,

I am trying to revive this patch, Foreign Key Arrays. The original proposal
from my GSoC 2017 days can be found here:
https://www.postgresql.org/message-id/CAJvoCut7zELHnBSC8HrM6p-R6q-NiBN1STKhqnK5fPE-9%3DGq3g%40mail.gmail.com

Disclaimer, I am not the original author of this patch, I picked up this
patch in 2017 to migrate the original patch from 2012 and add a GIN index
to make it usable as the performance without a GIN index is not usable
after 100 rows.
The original authors, Tom Lane and Marco Nenciarini, are the ones who did
most of the heavy lifting. The original discussion can be found here:
https://www.postgresql.org/message-id/flat/1343842863(dot)5162(dot)4(dot)camel%40greygoo(dot)devise-it(dot)lan#1343842863(dot)5162(dot)4(dot)camel(at)greygoo(dot)devise-it(dot)lan

*In brief, it would be used as follows:*
```sql
CREATE TABLE A ( atest1 int PRIMARY KEY, atest2 text );
CREATE TABLE B ( btest1 int[], btest2 int );
ALTER TABLE B ADD CONSTRAINT FKARRAY FOREIGN KEY (EACH ELEMENT OF
btest1) REFERENCES A;
```
and now table B references table A as follows:
```sql
INSERT INTO B VALUES ('{10,1}', 2);
```
where this row references rows 1 and 10 from A without the need of a
many-to-many table

*Changelog (since the last version, v8):*
- v9 (made compatible with Postgresql 11)
support `DeconstructFkConstraintRow`
support `CloneFkReferencing`
support `generate_operator_clause`

- v10 (made compatible with Postgresql v12)
support `addFkRecurseReferenced` and `addFkRecurseReferencing`
support `CloneFkReferenced` and `CloneFkReferencing`
migrate tests

- v11(make compatible with Postgresql v13)
drop `ConvertTriggerToFK`
drop `select_common_type_2args` in favor of `select_common_type_from_oids`
migrate tests

- v12(made compatible with current master, 2021-01-23,
commit a8ed6bb8f4cf259b95c1bff5da09a8f4c79dca46)
add ELEMENT to `bare_label_keyword`
migrate docs

*Todo:*
- re-add @>> operator which allows comparison of between array and element
and returns true iff the element is within the array
to allow easier select statements and lower overhead of explicitly creating
an array within the SELECT statement.

```diff
- SELECT * FROM B WHERE btest1 @> ARRAY[5];
+ SELECT * FROM B WHERE btest1 @>> 5;
```

I apologize it took so long to get a new version here (years). However,
this is not the first time I tried to migrate the patch, every time a
different issue blocked me from doing so.
Reviews and suggestions are most welcome, @Joel Jacobson
<joel(at)compiler(dot)org> please
review and test as previously agreed.

/Mark

On Tue, Oct 2, 2018 at 7:13 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> On Sat, Aug 11, 2018 at 05:20:57AM +0200, Mark Rofail wrote:
> > I am still having problems rebasing this patch. I can not figure it out
> on
> > my own.
>
> Okay, it's been a couple of months since this last email, and nothing
> has happened, so I am marking it as returned with feedback.
> --
> Michael
>