Re: Storing a dynahash for an entire connection or transaction?

Volkan YAZICI wrote:
>> What I'd like to do is change the way I store this hash so that it
>> doesn't need to be as frequently updated. I'm open to most any solution.
>> One type rarely ever has new values (maybe once every several months)
>> and the other gets new values once a night.
>
> You may want to cache these values using a static variable (which will
> make itself to be valid per session) that stores its values in the
> (for instance) TopTransactionContext.

That's the obvious solution (or perhaps in CurTransactionContext), but
when the function is called in a subsequent transaction, how does it
determine that the static pointer was allocated from a context which has
since vanished? I suppose that you could store the memory context
pointer for later comparison, but while it seems unlikely that you'd get
the same pointer twice in a row, that's not exactly a guarantee.

I note (reading src/backend/utils/mmgr/README) that there are reset and
delete methods attached to memory contexts, so perhaps the best way to
accomplish this would be to create a separate memory context as a child
of CurTransactionContext, and register a cleanup function which could
clear the static var when the context is torn down. I'm assuming that
those methods do get called in such cases, but I haven't delved much.

Cheers

Tom