"Bak @ kedai" wrote:
> > ZPYGre is not threadsafe, so with it and all non-threadsafe da's zope
> > uses a lock around access. (Thunked.py)
> >
> > The solution is to just use multiple DA connections and let postgres
> > sort out the concurrency issues.
> >
> i'm not clear about "use multiple DA connections".  let's say i have several
> sql methods.  it is meant for one particular app.  do i create a few  db
> connections and assign them to different sql methods?

i would factor your sql methods into logical groups and give dedicated
connections to groups which might have signifigant concurrent access.
Giving dedicated connections to every method is not productive as you
just increase concurrency problens on the db side. 

an example might be a dedicated connection for user related info,
sessions, etc. and another for a news system.

> anybody know whether PoPy is threadsafe already?

some reference regarding threadsafety as defined by the python dbi from
the db-sig group.

Integer constant stating the level of thread safety the interface
supports. Possible values are: 
            = Threads may not share the module.
            = Threads may share the module, but not connections.
            = Threads may share the module and connections.
            = Threads may share the module, connections and cursors.

         Sharing in the above context means that two threads may use a
resource without wrapping it using a mutex semaphore to
         implement resource locking. Note that you cannot always make
external resources thread safe by managing access using a
         mutex: the resource may rely on global variables or other
external sources that are beyond your control. 

First this is in regards to the underlying python lib that drives the
DA. both PyGre and PoPy are thread safety 1. Words have been said to the
effect that the developers of PoPy would like to raise the thread safety
of PoPy to 2. I'm not sure if D'arcy(author PyGre) has any such plans,
however he is a contributor to Postgres and does maintain PyGre.  PyGre
did not use to conform to the python DBI, since it was written to
support the features of Postgres, there is a now a wrapper around it
provide this abstraction. PoPy was built to support the python DBI. I
bring this info up because the DA for PyGre is dated and does not appear
to be supported, but its important to realize that this DA is just a
thin wrapper around the underlying db access lib, and for Postgres both
of these are being worked on.

if you really want a thread safe DA you're going to have to look towards
the commercial DBs. rumor has it that someone at DC is writing a new
Oracle adaptor.

> thanks and sorry to be a bone head :)

no worries, if people never asked than we would all be learning by trial
and error.

> > Cheers
> >
> > Kapil
> >

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