Re: MemoryContextCreate change in PG 11 how should contexts be created

Paul Ramsey <pramsey(at)cleverelephant(dot)ca> writes:
> Our use of MemoryContextCreate is solely in order to get use
> MemoryContextDelete as a callback so that, at the end of a statement,
> we can clean up externally allocated memory that we're holding in a
> cache. If we had some other callback to use for "the statement is
> complete, you can clean up now", we could avoid all this mucking
> around with raw MemoryContexts entirely. The MemoryContext trick/hack
> is very old, perhaps a callback or hook has been added since then that
> we could make use of?

I'm not managing to wrap my head around how you could use
MemoryContextCreate directly, unless you are implementing your own memory
context type, in which case the API changes aren't that difficult to make
I should think.

However, if the need is to free some external resources when a memory
context is destroyed, seems like what you ought to be using is a memory
context reset callback. Look at MemoryContextRegisterResetCallback and
its callers (there are just a couple at the moment, though I'm fooling
with a patch that will add more).

regards, tom lane