/*
* Receive a tuple from the executor and store it in the tuplestore.
* This is for the easy case where we don't have to detoast.
*/
static void
tstoreReceiveSlot_notoast(TupleTableSlot *slot, DestReceiver *self)
{
TStoreState *myState = (TStoreState *) self;
tuplestore_puttupleslot(myState->tstore, slot);
}
/*
* Receive a tuple from the executor and store it in the tuplestore.
* This is for the easy case where we don't have to detoast.
*/
static void
tstoreReceiveSlot_notoast(TupleTableSlot *slot, DestReceiver *self)
{
TStoreState *myState = (TStoreState *) self;
MemoryContext oldcxt = MemoryContextSwitchTo(myState->cxt);
tuplestore_puttupleslot(myState->tstore, slot);
MemoryContextSwitchTo(oldcxt);
}
/* ----------------------------------------------------------------
* 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;
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);
}
/* ----------------------------------------------------------------
* ExecRecursiveUnion(node)
*
* Scans the recursive query sequentially and returns the next
* qualifying tuple.
*
* 1. evaluate non recursive term and assign the result to RT
*
* 2. execute recursive terms
*
* 2.1 WT := RT
* 2.2 while WT is not empty repeat 2.3 to 2.6. if WT is empty returns RT
* 2.3 replace the name of recursive term with WT
* 2.4 evaluate the recursive term and store into WT
* 2.5 append WT to RT
* 2.6 go back to 2.2
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecRecursiveUnion(RecursiveUnionState *node)
{
PlanState *outerPlan = outerPlanState(node);
PlanState *innerPlan = innerPlanState(node);
RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
TupleTableSlot *slot;
RUHashEntry entry;
bool isnew;
/* 1. Evaluate non-recursive term */
if (!node->recursing)
{
for (;;)
{
slot = ExecProcNode(outerPlan);
if (TupIsNull(slot))
break;
if (plan->numCols > 0)
{
/* Find or build hashtable entry for this tuple's group */
entry = (RUHashEntry)
LookupTupleHashEntry(node->hashtable, slot, &isnew);
/* Must reset temp context after each hashtable lookup */
MemoryContextReset(node->tempContext);
/* Ignore tuple if already seen */
if (!isnew)
continue;
}
/* Each non-duplicate tuple goes to the working table ... */
tuplestore_puttupleslot(node->working_table, slot);
/* ... and to the caller */
return slot;
}
node->recursing = true;
}
/* 2. Execute recursive term */
for (;;)
{
slot = ExecProcNode(innerPlan);
if (TupIsNull(slot))
{
/* Done if there's nothing in the intermediate table */
if (node->intermediate_empty)
break;
/* done with old working table ... */
tuplestore_end(node->working_table);
/* intermediate table becomes working table */
node->working_table = node->intermediate_table;
/* create new empty intermediate table */
node->intermediate_table = tuplestore_begin_heap(false, false,
work_mem);
node->intermediate_empty = true;
/* reset the recursive term */
innerPlan->chgParam = bms_add_member(innerPlan->chgParam,
plan->wtParam);
/* and continue fetching from recursive term */
continue;
}
if (plan->numCols > 0)
{
/* Find or build hashtable entry for this tuple's group */
entry = (RUHashEntry)
LookupTupleHashEntry(node->hashtable, slot, &isnew);
/* Must reset temp context after each hashtable lookup */
MemoryContextReset(node->tempContext);
/* Ignore tuple if already seen */
if (!isnew)
continue;
}
/* Else, tuple is good; stash it in intermediate table ... */
node->intermediate_empty = false;
tuplestore_puttupleslot(node->intermediate_table, slot);
/* ... and return it */
return slot;
}
return NULL;
}
