Re: Serializable Snapshot Isolation

"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Heikki Linnakangas wrote:
>> That sounds like it can eat through your shared memory very quickly
>> if you have a lot of subtransactions.

> Hmmm.... I've never explicitly used subtransactions, so I don't tend
> to think of them routinely going too deep. And the struct is pretty
> small.

That assumption is absolutely, totally not going to fly.

>> Why not use SubTransGetTopmostTransaction() ?

> This needs to work when the xid of a transaction is found in the MVCC
> data of a tuple for any overlapping serializable transaction -- even
> if that transaction has completed and its connection has been
> closed. It didn't look to me like SubTransGetTopmostTransaction()
> would work after the transaction was gone.

Yes, it should work. If it doesn't, you are failing to manage the
TransactionXmin horizon correctly.

regards, tom lane