On Tue, Apr 07, 2009 at 01:26:31PM -0700, Maciej Katafiasz wrote:

> in the course of implementing the perec-backed store, we ran into an
> issue that needs a clarification as to what contract exactly holds
> between Weblocks and stores. The issue is that perec has a very strict
> requirement that *all* operations that touch the DB (including read DB-
> backed objects' slots at any time) must be wrapped in a transaction.
> However, it seems that Weblocks (or the grid widget anyway) tries to
> read persistent objects outside of a transaction. That doesn't end too
> well. Thus I'd like to request documentation and/or discussion of when
> exactly the stores can expected the transactions to be active,

Nowhere right now; there are no guarantees. I suggest
running the whole request in a perec txn if any of the stores
are found to be perec ones.


> who is responsible for activating and terminating transactions,

Only the user right now.


> and whether we're guaranteed not to end up in nested
> transactions

No guarantees like this, but you can easily guard against
this in the begin/commit/abort-transaction store API functions.


> or ones interleaved between different stores.

That's a bit tricky. You need to audit/test Weblocks and
perec somewhat to see where problems might arise.

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