Re: Listen / Notify rewrite

>> Calling this a creeping feature is quite a leap.
>
> It's true that the real creep is having the payload at all rather than
> not having it.

Not having the payload at all is like santa showing up without his bag
of toys. Instead, you have to drive/fly to the north pole where he just
came from to get them.

>
> One person described stuffing the payload with the primary key of the
> record being invalidated. This means the requirements have just gone
> from holding at most some small fixed number of records bounded by the
> number of tables or other shared data structures to holding a large
> number of records bounded only by the number of records in their
> tables which is usually much much larger.
>
> Now you're talking about making the payloads variable size, which
> means you need to do free space management within shared pages to keep
> track of how much space is free and available for reuse.
>
> So we've gone from a simple hash table of fixed size entries
> containing an oid or "name" datum where we expect the hash table to
> fit in memory and a simple lru can handle old pages that aren't part
> of the working set to something that's going to look a lot like a
> database table -- it has to handle reusing space in collections of
> variable size data and scale up to millions of entries.
>
> And I note someone else in the thread was suggesting it needed ACID
> properties which makes space reuse even more complex and will need
> something like vacuum to implement it.
>

I think the original OP was close. The structure can still be fixed
length but maybe we can bump it to 8k (BLCKSZ)?

--
Andrew Chernow
eSilo, LLC
every bit counts
http://www.esilo.com/