/*
* inv_open -- access an existing large object.
*
* Returns:
* Large object descriptor, appropriately filled in. The descriptor
* and subsidiary data are allocated in the specified memory context,
* which must be suitably long-lived for the caller's purposes.
*/
LargeObjectDesc *
inv_open(Oid lobjId, int flags, MemoryContext mcxt)
{
LargeObjectDesc *retval;
Snapshot snapshot = NULL;
int descflags = 0;
if (flags & INV_WRITE)
{
snapshot = NULL; /* instantaneous MVCC snapshot */
descflags = IFS_WRLOCK | IFS_RDLOCK;
}
else if (flags & INV_READ)
{
snapshot = GetActiveSnapshot();
descflags = IFS_RDLOCK;
}
else
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid flags for opening a large object: %d",
flags)));
/* Can't use LargeObjectExists here because we need to specify snapshot */
if (!myLargeObjectExists(lobjId, snapshot))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("large object %u does not exist", lobjId)));
/*
* We must register the snapshot in TopTransaction's resowner, because it
* must stay alive until the LO is closed rather than until the current
* portal shuts down. Do this after checking that the LO exists, to avoid
* leaking the snapshot if an error is thrown.
*/
if (snapshot)
snapshot = RegisterSnapshotOnOwner(snapshot,
TopTransactionResourceOwner);
/* All set, create a descriptor */
retval = (LargeObjectDesc *) MemoryContextAlloc(mcxt,
sizeof(LargeObjectDesc));
retval->id = lobjId;
retval->subid = GetCurrentSubTransactionId();
retval->offset = 0;
retval->snapshot = snapshot;
retval->flags = descflags;
return retval;
}
/*
* inv_open -- access an existing large object.
*
* Returns:
* Large object descriptor, appropriately filled in. The descriptor
* and subsidiary data are allocated in the specified memory context,
* which must be suitably long-lived for the caller's purposes.
*/
LargeObjectDesc *
inv_open(Oid lobjId, int flags, MemoryContext mcxt)
{
LargeObjectDesc *retval;
retval = (LargeObjectDesc *) MemoryContextAlloc(mcxt,
sizeof(LargeObjectDesc));
retval->id = lobjId;
retval->subid = GetCurrentSubTransactionId();
retval->offset = 0;
if (flags & INV_WRITE)
{
retval->snapshot = SnapshotNow;
retval->flags = IFS_WRLOCK | IFS_RDLOCK;
}
else if (flags & INV_READ)
{
/*
* We must register the snapshot in TopTransaction's resowner, because
* it must stay alive until the LO is closed rather than until the
* current portal shuts down.
*/
retval->snapshot = RegisterSnapshotOnOwner(GetActiveSnapshot(),
TopTransactionResourceOwner);
retval->flags = IFS_RDLOCK;
}
else
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid flags for opening a large object: %d",
flags)));
/* Can't use LargeObjectExists here because it always uses SnapshotNow */
if (!myLargeObjectExists(lobjId, retval->snapshot))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("large object %u does not exist", lobjId)));
return retval;
}
/*
* inv_open -- access an existing large object.
*
* Returns:
* Large object descriptor, appropriately filled in. The descriptor
* and subsidiary data are allocated in the specified memory context,
* which must be suitably long-lived for the caller's purposes.
*/
LargeObjectDesc *
inv_open(Oid lobjId, int flags, MemoryContext mcxt)
{
LargeObjectDesc *retval;
retval = (LargeObjectDesc *) MemoryContextAlloc(mcxt,
sizeof(LargeObjectDesc));
retval->id = lobjId;
retval->subid = GetCurrentSubTransactionId();
retval->offset = 0;
if (flags & INV_WRITE)
{
retval->snapshot = SnapshotNow;
retval->flags = IFS_WRLOCK | IFS_RDLOCK;
}
else if (flags & INV_READ)
{
/* be sure to copy snap into mcxt */
MemoryContext oldContext = MemoryContextSwitchTo(mcxt);
retval->snapshot = CopySnapshot(ActiveSnapshot);
retval->flags = IFS_RDLOCK;
MemoryContextSwitchTo(oldContext);
}
else
elog(ERROR, "invalid flags: %d", flags);
/* Can't use LargeObjectExists here because it always uses SnapshotNow */
if (!myLargeObjectExists(lobjId, retval->snapshot))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("large object %u does not exist", lobjId)));
return retval;
}