Re: [HACKERS] Re: SIGBUS in AllocSetAlloc & jdbc

> Hmm. The documentation does say somewhere that LO object handles are
> only good within a transaction ... so it's amazing this worked reliably
> under 6.4.x.
>
> Is there any way we could improve the backend's LO functions to defend
> against this sort of misuse, rather than blindly accepting a stale
> filehandle?

It should not be very difficult. We could explicitly close LO
filehandles on commits.

But I'm now not confident on this. From comments in be-fsstubs.c:

>Builtin functions for open/close/read/write operations on large objects.
>These functions operate in the current portal variable context, which
>means the large object descriptors hang around between transactions and
>are not deallocated until explicitly closed, or until the portal is
>closed.

If above is true, LO filehandles should be able to survive between
transactions.

Following data are included in them. My question is: Can these data
survive between transactions? I guess not.

typedef struct LargeObjectDesc
{
Relation heap_r; /* heap relation */
Relation index_r; /* index relation on seqno attribute */
IndexScanDesc iscan; /* index scan we're using */
TupleDesc hdesc; /* heap relation tuple desc */
TupleDesc idesc; /* index relation tuple desc */

[snip]