Re: Patch to support SEMI and ANTI join removal

On 09/16/2014 01:20 PM, David Rowley wrote:
> + /*
> + * We mustn't allow any joins to be removed if there are any pending
> + * foreign key triggers in the queue. This could happen if we are planning
> + * a query that has been executed from within a volatile function and the
> + * query which called this volatile function has made some changes to a
> + * table referenced by a foreign key. The reason for this is that any
> + * updates to a table which is referenced by a foreign key constraint will
> + * only have the referencing tables updated after the command is complete,
> + * so there is a window of time where records may violate the foreign key
> + * constraint.
> + *
> + * Currently this code is quite naive, as we won't even attempt to remove
> + * the join if there are *any* pending foreign key triggers, on any
> + * relation. It may be worthwhile to improve this to check if there's any
> + * pending triggers for the referencing relation in the join.
> + */
> + if (!AfterTriggerQueueIsEmpty())
> + return false;

Hmm. This code runs when the query is planned. There is no guarantee
that there won't be after triggers pending when the query is later
*executed*.

- Heikki