Re: proposal: make NOTIFY list de-duplication optional

On 02/05/2016 08:49 PM, Tom Lane wrote:

> Yeah, I agree that a GUC for this is quite unappetizing.

Agreed.

>
> One idea would be to build a hashtable to aid with duplicate detection
> (perhaps only once the pending-notify list gets long).
>
> Another thought is that it's already the case that duplicate detection is
> something of a "best effort" activity; note for example the comment in
> AsyncExistsPendingNotify pointing out that we don't collapse duplicates
> across subtransactions.  Would it be acceptable to relax the standards
> a bit further?  For example, if we only checked for duplicates among the
> last N notification list entries (for N say around 100), we'd probably
> cover just about all the useful cases, and the runtime would stay linear.
> The data structure isn't tremendously conducive to that, but it could be
> done.
>
>             


I like the hashtable idea if it can be made workable.

cheers

andrew