Re: truncate in combination with deferred triggers

Markus Schiltknecht <markus@bluegap.ch> writes:
> CREATE TABLE category (
>      id INT PRIMARY KEY,
>      name TEXT);

> CREATE TABLE category_todo (
>      cat_id INT REFERENCES category(id)
>          DEFERRABLE INITIALLY DEFERRED
> );

> BEGIN;

> INSERT INTO category (id, name) VALUES (0, 'test');
> INSERT INTO category_todo (cat_id) VALUES (0);
> TRUNCATE category_todo;

> COMMIT;

> -- COMMIT fails with: 'failed to fetch new tuple for AFTER trigger'

Hm.  At least for this case, it seems the nicest behavior would be for
TRUNCATE to scan the deferred-triggers list and just throw away any
pending trigger firings for the target table(s).  I wonder however
whether there are cases where that would be a bad idea.  It might be
safer for the TRUNCATE to error out if there are any pending triggers.
Stephan, any thoughts about it?

            regards, tom lane