Re: losing my large objects with Postgresql 8.1.4

thank you Tom!
that did the trick!
I'm still in the dark why my test data type didn't exhibit the
problem, but I'm certainly a much happier camper now.

Eric.
At 05:40 PM 05/01/2007, Tom Lane wrote:
>Eric Davies <Eric(at)barrodale(dot)com> writes:
> > Some of my custom server functions/data types that work correctly
> > under Postgresql 8.0.1 are having trouble with lost large objects
> > under Postgresql 8.1.4 and Postgresql 8.1.5, but only in particular
> > usages.
>
> > When I execute the following sequence of commands:
> > select MyTypeToText( BuildMyType('asdf'));
> > I get the following error
> > ERROR: large object 33016 does not exist
> > \lo_list (in psql) doesn't show any new large objects.
>
>MyTypeToText is probably referencing a start-of-statement snapshot,
>in which the LO doesn't exist yet. This is a consequence of making
>read-only accesses to LOs be MVCC-compliant. Probably your best bet
>for working around it is to open the LO in read/write mode, even if
>you don't intend to write it --- that will make the behavior like 8.0.
>
>Relevant 8.1 release note:
>
> Read-only large object descriptors now obey MVCC snapshot semantics
>
> When a large object is opened with INV_READ (and not INV_WRITE),
> the data read from the descriptor will now reflect a "snapshot" of
> the large object's state at the time of the transaction snapshot in
> use by the query that called lo_open(). To obtain the old behavior
> of always returning the latest committed data, include INV_WRITE in
> the mode flags for lo_open().
>
>
> regards, tom lane
>
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Eric Davies, M.Sc.
Barrodale Computing Services Ltd.
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Email: eric(at)barrodale(dot)com
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