/* ----------------------------------------------------------------
* CteScanNext
*
* This is a workhorse for ExecCteScan
* ----------------------------------------------------------------
*/
static TupleTableSlot *
CteScanNext(CteScanState *node)
{
EState *estate;
ScanDirection dir;
bool forward;
Tuplestorestate *tuplestorestate;
bool eof_tuplestore;
TupleTableSlot *slot;
/*
* get state info from node
*/
estate = node->ss.ps.state;
dir = estate->es_direction;
forward = ScanDirectionIsForward(dir);
tuplestorestate = node->leader->cte_table;
tuplestore_select_read_pointer(tuplestorestate, node->readptr);
slot = node->ss.ss_ScanTupleSlot;
/*
* If we are not at the end of the tuplestore, or are going backwards, try
* to fetch a tuple from tuplestore.
*/
eof_tuplestore = tuplestore_ateof(tuplestorestate);
if (!forward && eof_tuplestore)
{
if (!node->leader->eof_cte)
{
/*
* When reversing direction at tuplestore EOF, the first
* gettupleslot call will fetch the last-added tuple; but we want
* to return the one before that, if possible. So do an extra
* fetch.
*/
if (!tuplestore_advance(tuplestorestate, forward))
return NULL; /* the tuplestore must be empty */
}
eof_tuplestore = false;
}
/*
* If we can fetch another tuple from the tuplestore, return it.
*
* Note: we have to use copy=true in the tuplestore_gettupleslot call,
* because we are sharing the tuplestore with other nodes that might write
* into the tuplestore before we get called again.
*/
if (!eof_tuplestore)
{
if (tuplestore_gettupleslot(tuplestorestate, forward, true, slot))
return slot;
if (forward)
eof_tuplestore = true;
}
/*
* If necessary, try to fetch another row from the CTE query.
*
* Note: the eof_cte state variable exists to short-circuit further calls
* of the CTE plan. It's not optional, unfortunately, because some plan
* node types are not robust about being called again when they've already
* returned NULL.
*/
if (eof_tuplestore && !node->leader->eof_cte)
{
TupleTableSlot *cteslot;
/*
* We can only get here with forward==true, so no need to worry about
* which direction the subplan will go.
*/
cteslot = ExecProcNode(node->cteplanstate);
if (TupIsNull(cteslot))
{
node->leader->eof_cte = true;
return NULL;
}
/*
* There are corner cases where the subplan could change which
* tuplestore read pointer is active, so be sure to reselect ours
* before storing the tuple we got.
*/
tuplestore_select_read_pointer(tuplestorestate, node->readptr);
/*
* Append a copy of the returned tuple to tuplestore. NOTE: because
* our read pointer is certainly in EOF state, its read position will
* move forward over the added tuple. This is what we want. Also,
* any other readers will *not* move past the new tuple, which is what
* they want.
*/
tuplestore_puttupleslot(tuplestorestate, cteslot);
/*
* We MUST copy the CTE query's output tuple into our own slot. This
* is because other CteScan nodes might advance the CTE query before
* we are called again, and our output tuple must stay stable over
* that.
*/
return ExecCopySlot(slot, cteslot);
}
/*
* Nothing left ...
*/
return ExecClearTuple(slot);
}
/* ----------------------------------------------------------------
* ExecMaterial
*
* As long as we are at the end of the data collected in the tuplestore,
* we collect one new row from the subplan on each call, and stash it
* aside in the tuplestore before returning it. The tuplestore is
* only read if we are asked to scan backwards, rescan, or mark/restore.
*
* ----------------------------------------------------------------
*/
TupleTableSlot * /* result tuple from subplan */
ExecMaterial(MaterialState *node)
{
EState *estate;
ScanDirection dir;
bool forward;
Tuplestorestate *tuplestorestate;
HeapTuple heapTuple = NULL;
bool should_free = false;
bool eof_tuplestore;
TupleTableSlot *slot;
/*
* get state info from node
*/
estate = node->ss.ps.state;
dir = estate->es_direction;
forward = ScanDirectionIsForward(dir);
tuplestorestate = (Tuplestorestate *) node->tuplestorestate;
/*
* If first time through, and we need a tuplestore, initialize it.
*/
if (tuplestorestate == NULL && node->randomAccess)
{
tuplestorestate = tuplestore_begin_heap(true, false, work_mem);
node->tuplestorestate = (void *) tuplestorestate;
}
/*
* If we are not at the end of the tuplestore, or are going backwards, try
* to fetch a tuple from tuplestore.
*/
eof_tuplestore = (tuplestorestate == NULL) ||
tuplestore_ateof(tuplestorestate);
if (!forward && eof_tuplestore)
{
if (!node->eof_underlying)
{
/*
* When reversing direction at tuplestore EOF, the first
* getheaptuple call will fetch the last-added tuple; but we want
* to return the one before that, if possible. So do an extra
* fetch.
*/
heapTuple = tuplestore_getheaptuple(tuplestorestate,
forward,
&should_free);
if (heapTuple == NULL)
return NULL; /* the tuplestore must be empty */
if (should_free)
heap_freetuple(heapTuple);
}
eof_tuplestore = false;
}
if (!eof_tuplestore)
{
heapTuple = tuplestore_getheaptuple(tuplestorestate,
forward,
&should_free);
if (heapTuple == NULL && forward)
eof_tuplestore = true;
}
/*
* If necessary, try to fetch another row from the subplan.
*
* Note: the eof_underlying state variable exists to short-circuit further
* subplan calls. It's not optional, unfortunately, because some plan
* node types are not robust about being called again when they've already
* returned NULL.
*/
if (eof_tuplestore && !node->eof_underlying)
{
PlanState *outerNode;
TupleTableSlot *outerslot;
/*
* We can only get here with forward==true, so no need to worry about
* which direction the subplan will go.
*/
outerNode = outerPlanState(node);
outerslot = ExecProcNode(outerNode);
if (TupIsNull(outerslot))
{
node->eof_underlying = true;
return NULL;
}
heapTuple = ExecFetchSlotTuple(outerslot);
should_free = false;
/*
* Append returned tuple to tuplestore, too. NOTE: because the
* tuplestore is certainly in EOF state, its read position will move
* forward over the added tuple. This is what we want.
*/
if (tuplestorestate)
tuplestore_puttuple(tuplestorestate, (void *) heapTuple);
}
/*
* Return the obtained tuple, if any.
*/
slot = (TupleTableSlot *) node->ss.ps.ps_ResultTupleSlot;
if (heapTuple)
return ExecStoreTuple(heapTuple, slot, InvalidBuffer, should_free);
else
return ExecClearTuple(slot);
}
/* ----------------------------------------------------------------
* ExecMaterial
*
* As long as we are at the end of the data collected in the tuplestore,
* we collect one new row from the subplan on each call, and stash it
* aside in the tuplestore before returning it. The tuplestore is
* only read if we are asked to scan backwards, rescan, or mark/restore.
*
* ----------------------------------------------------------------
*/
TupleTableSlot * /* result tuple from subplan */
ExecMaterial(MaterialState *node)
{
EState *estate;
ScanDirection dir;
bool forward;
Tuplestorestate *tuplestorestate;
bool eof_tuplestore;
TupleTableSlot *slot;
/*
* get state info from node
*/
estate = node->ss.ps.state;
dir = estate->es_direction;
forward = ScanDirectionIsForward(dir);
tuplestorestate = node->tuplestorestate;
/*
* If first time through, and we need a tuplestore, initialize it.
*/
if (tuplestorestate == NULL && node->eflags != 0)
{
tuplestorestate = tuplestore_begin_heap(true, false, work_mem);
tuplestore_set_eflags(tuplestorestate, node->eflags);
if (node->eflags & EXEC_FLAG_MARK)
{
/*
* Allocate a second read pointer to serve as the mark. We know it
* must have index 1, so needn't store that.
*/
int ptrno PG_USED_FOR_ASSERTS_ONLY;
ptrno = tuplestore_alloc_read_pointer(tuplestorestate,
node->eflags);
Assert(ptrno == 1);
}
node->tuplestorestate = tuplestorestate;
}
/*
* If we are not at the end of the tuplestore, or are going backwards, try
* to fetch a tuple from tuplestore.
*/
eof_tuplestore = (tuplestorestate == NULL) ||
tuplestore_ateof(tuplestorestate);
if (!forward && eof_tuplestore)
{
if (!node->eof_underlying)
{
/*
* When reversing direction at tuplestore EOF, the first
* gettupleslot call will fetch the last-added tuple; but we want
* to return the one before that, if possible. So do an extra
* fetch.
*/
if (!tuplestore_advance(tuplestorestate, forward))
return NULL; /* the tuplestore must be empty */
}
eof_tuplestore = false;
}
/*
* If we can fetch another tuple from the tuplestore, return it.
*/
slot = node->ss.ps.ps_ResultTupleSlot;
if (!eof_tuplestore)
{
if (tuplestore_gettupleslot(tuplestorestate, forward, false, slot))
return slot;
if (forward)
eof_tuplestore = true;
}
/*
* If necessary, try to fetch another row from the subplan.
*
* Note: the eof_underlying state variable exists to short-circuit further
* subplan calls. It's not optional, unfortunately, because some plan
* node types are not robust about being called again when they've already
* returned NULL.
*/
if (eof_tuplestore && !node->eof_underlying)
{
PlanState *outerNode;
TupleTableSlot *outerslot;
/*
* We can only get here with forward==true, so no need to worry about
* which direction the subplan will go.
*/
outerNode = outerPlanState(node);
outerslot = ExecProcNode(outerNode);
if (TupIsNull(outerslot))
{
node->eof_underlying = true;
return NULL;
}
/*
* Append a copy of the returned tuple to tuplestore. NOTE: because
* the tuplestore is certainly in EOF state, its read position will
* move forward over the added tuple. This is what we want.
*/
if (tuplestorestate)
tuplestore_puttupleslot(tuplestorestate, outerslot);
/*
* We can just return the subplan's returned tuple, without copying.
*/
return outerslot;
}
/*
* Nothing left ...
*/
return ExecClearTuple(slot);
}
