Re: Is element access after HASH_REMOVE ever OK?

I wrote:
> ...  Can we get rid of the unsafe
> access easily?

Oh, shoulda read your second patch first.  Looking at that,
I fear it might not be quite that simple, because the
comment on CheckAndSetLockHeld says very clearly

 * It is callers responsibility that this function is called after
 * acquiring/releasing the relation extension/page lock.

so your proposed patch violates that specification.

I'm inclined to think that this API spec is very poorly thought out
and should be changed --- why is it that the flags should change
*after* the lock change in both directions?  But we'd have to take
a look at the usage of these flags to understand what's going on
exactly.

            regards, tom lane