
> I'm not sure if you're confusing backend-local hashes with shared
> hashes, or hash control headers with the actual shared data.  But
> the above is a false statement.  DynaHashCxt is not shared.

No, wasn't confused over that. Was confused over something else though :-)

 
> Shared hashes are a bit tricky because there is a backend-local
> structure that has a pointer into the shared memory --- is that
> what's confusing you?

That's pretty much right on the mark, and the heart of the problem I
suspect. 

So this means we'll have to pull relHash out of the shared FreeSpaceMap
structure and make it a variable in it's own right? [Same goes for lockHash
and proclockHash in the LockMethod structure reference by "LockTable (lock
method table)"]


> Keep in mind that this code did work in a fork/exec context not
> so many moons ago.  If you think you see a showstopper, it's a
> relatively recent change and can be undone.

Keeping this firmly in mind, trust me.

Thanks,
Claudio

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Wed, 3 Dec 2003 15:48:42 +1100 
Claudio Natoli <claudio.natoli@memetrics.com>
Re: [HACKERS] fork/exec problem: DynaHashCxt 
Claudio Natoli <claudio.natoli@memetrics.com> writes:
> So this means we'll have to pull relHash out of the shared FreeSpaceMap
> structure and make it a variable in it's own right?

Hm.  The freespace.c code is relatively new and might not be jumping
through all of the hoops it should be jumping through.  My recollection
of the older code is that the logic was like "create or attach to shared
memory structure named 'foo', if not create then initialize the shared
structure".  I'll take the blame if freespace.c doesn't do this right...

> [Same goes for lockHash and proclockHash in the LockMethod structure
> reference by "LockTable (lock method table)"]

The lock code *should* be doing this right, unless I've totally
forgotten the modification history ...

			regards, tom lane

Wed, 03 Dec 2003 00:01:53 -0500
Tom Lane <tgl@sss.pgh.pa.us>
Re: [HACKERS] fork/exec problem: DynaHashCxt 