Re: Caching of Queries

"Aaron Werman" <awerman2@hotmail.com> writes:
> I imagine a design where a shared plan cache would consist of the plans,
> indexed by a statement hash and again by dependant objects.  A statement to
> be planned would be hashed and matched to the cache. DDL would need to
> synchronously destroy all dependant plans. If each plan maintains a validity
  ^^^^^^^^^^^^^
> flag, changing the cache wouldn't have to block so I don't see where there
                           ^^^^^^^^^^^^^^^^^^^^^^
> would be contention.

You have contention to access a shared data structure *at all* -- for
instance readers must lock out writers.  Or didn't you notice the self-
contradictions in what you just said?

Our current scalability problems dictate reducing such contention, not
adding whole new sources of it.

            regards, tom lane