Re: Large Objects in serializable transaction question

=?iso-8859-1?Q? "Andreas=20Sch=F6nbach" ?= <andreasschoenbach(at)web(dot)de> writes:
> I have a testprogram (using libpq) reading data from a cursor and large objects according to the result of the cursor. The cursor is opened in a serializable transaction.
> Just for test reasons I know tried the following:
> I started the test program that reads the data from the cursor and that reads the large objects according to the result of the fetch. While the test was running I now was dropping all large objects in a parallel session. Since I am using a serializable transaction in the test program I still should be able to read all the large objects, even if I drop them in a parallel session. But it does not work. I get an error, that the large object can't be opened.

Yeah. The large object operations use SnapshotNow (effectively
read-committed) rather than looking at the surrounding transaction's
snapshot. This is a bug IMHO, but no one's got round to working on
it. (It's not entirely clear how the LO functions could access the
appropriate snapshot.)

regards, tom lane