/*
* PersistHoldablePortal
*
* Prepare the specified Portal for access outside of the current
* transaction. When this function returns, all future accesses to the
* portal must be done via the Tuplestore (not by invoking the
* executor).
*/
void
PersistHoldablePortal(Portal portal)
{
QueryDesc *queryDesc = PortalGetQueryDesc(portal);
Portal saveActivePortal;
ResourceOwner saveResourceOwner;
MemoryContext savePortalContext;
MemoryContext oldcxt;
/*
* If we're preserving a holdable portal, we had better be inside the
* transaction that originally created it.
*/
Assert(portal->createSubid != InvalidSubTransactionId);
Assert(queryDesc != NULL);
/*
* Caller must have created the tuplestore already.
*/
Assert(portal->holdContext != NULL);
Assert(portal->holdStore != NULL);
/*
* Before closing down the executor, we must copy the tupdesc into
* long-term memory, since it was created in executor memory.
*/
oldcxt = MemoryContextSwitchTo(portal->holdContext);
portal->tupDesc = CreateTupleDescCopy(portal->tupDesc);
MemoryContextSwitchTo(oldcxt);
/*
* Check for improper portal use, and mark portal active.
*/
if (portal->status != PORTAL_READY)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("portal \"%s\" cannot be run", portal->name)));
portal->status = PORTAL_ACTIVE;
/*
* Set up global portal context pointers.
*/
saveActivePortal = ActivePortal;
saveResourceOwner = CurrentResourceOwner;
savePortalContext = PortalContext;
PG_TRY();
{
ActivePortal = portal;
CurrentResourceOwner = portal->resowner;
PortalContext = PortalGetHeapMemory(portal);
MemoryContextSwitchTo(PortalContext);
PushActiveSnapshot(queryDesc->snapshot);
/*
* Rewind the executor: we need to store the entire result set in the
* tuplestore, so that subsequent backward FETCHs can be processed.
*/
ExecutorRewind(queryDesc);
/*
* Change the destination to output to the tuplestore. Note we tell
* the tuplestore receiver to detoast all data passed through it.
*/
queryDesc->dest = CreateDestReceiver(DestTuplestore);
SetTuplestoreDestReceiverParams(queryDesc->dest,
portal->holdStore,
portal->holdContext,
true);
/* Fetch the result set into the tuplestore */
ExecutorRun(queryDesc, ForwardScanDirection, 0L);
(*queryDesc->dest->rDestroy) (queryDesc->dest);
queryDesc->dest = NULL;
/*
* Now shut down the inner executor.
*/
portal->queryDesc = NULL; /* prevent double shutdown */
/* we do not need AfterTriggerEndQuery() here */
ExecutorEnd(queryDesc);
FreeQueryDesc(queryDesc);
/*
* Set the position in the result set: ideally, this could be
* implemented by just skipping straight to the tuple # that we need
* to be at, but the tuplestore API doesn't support that. So we start
* at the beginning of the tuplestore and iterate through it until we
* reach where we need to be. FIXME someday? (Fortunately, the
* typical case is that we're supposed to be at or near the start of
* the result set, so this isn't as bad as it sounds.)
*/
MemoryContextSwitchTo(portal->holdContext);
if (portal->atEnd)
{
/* we can handle this case even if posOverflow */
while (tuplestore_advance(portal->holdStore, true))
/* continue */ ;
}
else
{
long store_pos;
if (portal->posOverflow) /* oops, cannot trust portalPos */
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("could not reposition held cursor")));
tuplestore_rescan(portal->holdStore);
for (store_pos = 0; store_pos < portal->portalPos; store_pos++)
{
if (!tuplestore_advance(portal->holdStore, true))
elog(ERROR, "unexpected end of tuple stream");
}
}
}
PG_CATCH();
{
/* Uncaught error while executing portal: mark it dead */
portal->status = PORTAL_FAILED;
/* Restore global vars and propagate error */
ActivePortal = saveActivePortal;
CurrentResourceOwner = saveResourceOwner;
PortalContext = savePortalContext;
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcxt);
/* Mark portal not active */
portal->status = PORTAL_READY;
ActivePortal = saveActivePortal;
CurrentResourceOwner = saveResourceOwner;
PortalContext = savePortalContext;
PopActiveSnapshot();
/*
* We can now release any subsidiary memory of the portal's heap context;
* we'll never use it again. The executor already dropped its context,
* but this will clean up anything that glommed onto the portal's heap via
* PortalContext.
*/
MemoryContextDeleteChildren(PortalGetHeapMemory(portal));
}
/*
* PersistHoldablePortal
*
* Prepare the specified Portal for access outside of the current
* transaction. When this function returns, all future accesses to the
* portal must be done via the Tuplestore (not by invoking the
* executor).
*/
void
PersistHoldablePortal(Portal portal)
{
QueryDesc *queryDesc = PortalGetQueryDesc(portal);
Portal saveActivePortal;
ResourceOwner saveResourceOwner;
MemoryContext savePortalContext;
MemoryContext oldcxt;
/*
* If we're preserving a holdable portal, we had better be inside the
* transaction that originally created it.
*/
Assert(portal->createSubid != InvalidSubTransactionId);
Assert(queryDesc != NULL);
/*
* Caller must have created the tuplestore already ... but not a snapshot.
*/
Assert(portal->holdContext != NULL);
Assert(portal->holdStore != NULL);
Assert(portal->holdSnapshot == NULL);
/*
* Before closing down the executor, we must copy the tupdesc into
* long-term memory, since it was created in executor memory.
*/
oldcxt = MemoryContextSwitchTo(portal->holdContext);
portal->tupDesc = CreateTupleDescCopy(portal->tupDesc);
MemoryContextSwitchTo(oldcxt);
/*
* Check for improper portal use, and mark portal active.
*/
MarkPortalActive(portal);
/*
* Set up global portal context pointers.
*/
saveActivePortal = ActivePortal;
saveResourceOwner = CurrentResourceOwner;
savePortalContext = PortalContext;
PG_TRY();
{
ActivePortal = portal;
if (portal->resowner)
CurrentResourceOwner = portal->resowner;
PortalContext = PortalGetHeapMemory(portal);
MemoryContextSwitchTo(PortalContext);
PushActiveSnapshot(queryDesc->snapshot);
/*
* Rewind the executor: we need to store the entire result set in the
* tuplestore, so that subsequent backward FETCHs can be processed.
*/
ExecutorRewind(queryDesc);
/*
* Change the destination to output to the tuplestore. Note we tell
* the tuplestore receiver to detoast all data passed through it; this
* makes it safe to not keep a snapshot associated with the data.
*/
queryDesc->dest = CreateDestReceiver(DestTuplestore);
SetTuplestoreDestReceiverParams(queryDesc->dest,
portal->holdStore,
portal->holdContext,
true);
/* Fetch the result set into the tuplestore */
ExecutorRun(queryDesc, ForwardScanDirection, 0L);
(*queryDesc->dest->rDestroy) (queryDesc->dest);
queryDesc->dest = NULL;
/*
* Now shut down the inner executor.
*/
portal->queryDesc = NULL; /* prevent double shutdown */
ExecutorFinish(queryDesc);
ExecutorEnd(queryDesc);
FreeQueryDesc(queryDesc);
/*
* Set the position in the result set.
*/
MemoryContextSwitchTo(portal->holdContext);
if (portal->atEnd)
{
/*
* Just force the tuplestore forward to its end. The size of the
* skip request here is arbitrary.
*/
while (tuplestore_skiptuples(portal->holdStore, 1000000, true))
/* continue */ ;
}
else
{
tuplestore_rescan(portal->holdStore);
if (!tuplestore_skiptuples(portal->holdStore,
portal->portalPos,
true))
elog(ERROR, "unexpected end of tuple stream");
}
}
PG_CATCH();
{
/* Uncaught error while executing portal: mark it dead */
MarkPortalFailed(portal);
/* Restore global vars and propagate error */
ActivePortal = saveActivePortal;
CurrentResourceOwner = saveResourceOwner;
PortalContext = savePortalContext;
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcxt);
/* Mark portal not active */
portal->status = PORTAL_READY;
ActivePortal = saveActivePortal;
CurrentResourceOwner = saveResourceOwner;
PortalContext = savePortalContext;
PopActiveSnapshot();
/*
* We can now release any subsidiary memory of the portal's heap context;
* we'll never use it again. The executor already dropped its context,
* but this will clean up anything that glommed onto the portal's heap via
* PortalContext.
*/
MemoryContextDeleteChildren(PortalGetHeapMemory(portal));
}
