Ensure we don't have duplicated columns in update (Fixes #2651)

[kieranajp]

Hi,

I noticed that an erroneous update query was being generated in my application (using the Postgres driver), similar to the error described in #2651:

ERROR:  multiple assignments to same column "column_id"
STATEMENT:  UPDATE "tasks" SET "column_id" = $2, "column_id" = $3, "task_position" = $4 WHERE "id" IN ($1)

I did a bit of digging and was able to narrow it down to this updatedColumns array not having a uniqueness check.

I'm not sure exactly what it is about my entity structure that triggers this, but I added a sanity check anyway. Please let me know if there's anything I can do to help get this merged.

Cheers,
--Kieran

[imnotjames]

Won't this fail with having too many parameters, then?

Also, could you rebase this against master so we can see the tests running? :)

[kieranajp]

Good question - honestly I don't remember. We ended up switching away from Node for the backend of this particular application so I'm afraid I don't have a way to repro this anymore.

Rebase incoming anyway.

[imnotjames]

This needs tests to confirm the behavior. If you can't reproduce it that might be an issue.

[HctrM]

I've also encountered this issue with Postgres driver and saving a relation with the foreign key ref. Looking forward to bug fix.

[imnotjames]

This PR has been stale a while without tests. We can't merge in code without confirming it resolves the underlying issue.

Closing out.