Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1186 insertions, 0 deletions

diff --git a/src/backend/executor/nodeAppend.c b/src/backend/executor/nodeAppend.c
new file mode 100644
index 0000000..6a2daa6
--- /dev/null
+++ b/src/backend/executor/nodeAppend.c
@@ -0,0 +1,1186 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeAppend.c
+ *	  routines to handle append nodes.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeAppend.c
+ *
+ *-------------------------------------------------------------------------
+ */
+/* INTERFACE ROUTINES
+ *		ExecInitAppend	- initialize the append node
+ *		ExecAppend		- retrieve the next tuple from the node
+ *		ExecEndAppend	- shut down the append node
+ *		ExecReScanAppend - rescan the append node
+ *
+ *	 NOTES
+ *		Each append node contains a list of one or more subplans which
+ *		must be iteratively processed (forwards or backwards).
+ *		Tuples are retrieved by executing the 'whichplan'th subplan
+ *		until the subplan stops returning tuples, at which point that
+ *		plan is shut down and the next started up.
+ *
+ *		Append nodes don't make use of their left and right
+ *		subtrees, rather they maintain a list of subplans so
+ *		a typical append node looks like this in the plan tree:
+ *
+ *				   ...
+ *				   /
+ *				Append -------+------+------+--- nil
+ *				/	\		  |		 |		|
+ *			  nil	nil		 ...    ...    ...
+ *								 subplans
+ *
+ *		Append nodes are currently used for unions, and to support
+ *		inheritance queries, where several relations need to be scanned.
+ *		For example, in our standard person/student/employee/student-emp
+ *		example, where student and employee inherit from person
+ *		and student-emp inherits from student and employee, the
+ *		query:
+ *
+ *				select name from person
+ *
+ *		generates the plan:
+ *
+ *				  |
+ *				Append -------+-------+--------+--------+
+ *				/	\		  |		  |		   |		|
+ *			  nil	nil		 Scan	 Scan	  Scan	   Scan
+ *							  |		  |		   |		|
+ *							person employee student student-emp
+ */
+
+#include "postgres.h"
+
+#include "executor/execAsync.h"
+#include "executor/execdebug.h"
+#include "executor/execPartition.h"
+#include "executor/nodeAppend.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "storage/latch.h"
+
+/* Shared state for parallel-aware Append. */
+struct ParallelAppendState
+{
+	LWLock		pa_lock;		/* mutual exclusion to choose next subplan */
+	int			pa_next_plan;	/* next plan to choose by any worker */
+
+	/*
+	 * pa_finished[i] should be true if no more workers should select subplan
+	 * i.  for a non-partial plan, this should be set to true as soon as a
+	 * worker selects the plan; for a partial plan, it remains false until
+	 * some worker executes the plan to completion.
+	 */
+	bool		pa_finished[FLEXIBLE_ARRAY_MEMBER];
+};
+
+#define INVALID_SUBPLAN_INDEX		-1
+#define EVENT_BUFFER_SIZE			16
+
+static TupleTableSlot *ExecAppend(PlanState *pstate);
+static bool choose_next_subplan_locally(AppendState *node);
+static bool choose_next_subplan_for_leader(AppendState *node);
+static bool choose_next_subplan_for_worker(AppendState *node);
+static void mark_invalid_subplans_as_finished(AppendState *node);
+static void ExecAppendAsyncBegin(AppendState *node);
+static bool ExecAppendAsyncGetNext(AppendState *node, TupleTableSlot **result);
+static bool ExecAppendAsyncRequest(AppendState *node, TupleTableSlot **result);
+static void ExecAppendAsyncEventWait(AppendState *node);
+static void classify_matching_subplans(AppendState *node);
+
+/* ----------------------------------------------------------------
+ *		ExecInitAppend
+ *
+ *		Begin all of the subscans of the append node.
+ *
+ *	   (This is potentially wasteful, since the entire result of the
+ *		append node may not be scanned, but this way all of the
+ *		structures get allocated in the executor's top level memory
+ *		block instead of that of the call to ExecAppend.)
+ * ----------------------------------------------------------------
+ */
+AppendState *
+ExecInitAppend(Append *node, EState *estate, int eflags)
+{
+	AppendState *appendstate = makeNode(AppendState);
+	PlanState **appendplanstates;
+	Bitmapset  *validsubplans;
+	Bitmapset  *asyncplans;
+	int			nplans;
+	int			nasyncplans;
+	int			firstvalid;
+	int			i,
+				j;
+
+	/* check for unsupported flags */
+	Assert(!(eflags & EXEC_FLAG_MARK));
+
+	/*
+	 * create new AppendState for our append node
+	 */
+	appendstate->ps.plan = (Plan *) node;
+	appendstate->ps.state = estate;
+	appendstate->ps.ExecProcNode = ExecAppend;
+
+	/* Let choose_next_subplan_* function handle setting the first subplan */
+	appendstate->as_whichplan = INVALID_SUBPLAN_INDEX;
+	appendstate->as_syncdone = false;
+	appendstate->as_begun = false;
+
+	/* If run-time partition pruning is enabled, then set that up now */
+	if (node->part_prune_info != NULL)
+	{
+		PartitionPruneState *prunestate;
+
+		/* We may need an expression context to evaluate partition exprs */
+		ExecAssignExprContext(estate, &appendstate->ps);
+
+		/* Create the working data structure for pruning. */
+		prunestate = ExecCreatePartitionPruneState(&appendstate->ps,
+												   node->part_prune_info);
+		appendstate->as_prune_state = prunestate;
+
+		/* Perform an initial partition prune, if required. */
+		if (prunestate->do_initial_prune)
+		{
+			/* Determine which subplans survive initial pruning */
+			validsubplans = ExecFindInitialMatchingSubPlans(prunestate,
+															list_length(node->appendplans));
+
+			nplans = bms_num_members(validsubplans);
+		}
+		else
+		{
+			/* We'll need to initialize all subplans */
+			nplans = list_length(node->appendplans);
+			Assert(nplans > 0);
+			validsubplans = bms_add_range(NULL, 0, nplans - 1);
+		}
+
+		/*
+		 * When no run-time pruning is required and there's at least one
+		 * subplan, we can fill as_valid_subplans immediately, preventing
+		 * later calls to ExecFindMatchingSubPlans.
+		 */
+		if (!prunestate->do_exec_prune && nplans > 0)
+			appendstate->as_valid_subplans = bms_add_range(NULL, 0, nplans - 1);
+	}
+	else
+	{
+		nplans = list_length(node->appendplans);
+
+		/*
+		 * When run-time partition pruning is not enabled we can just mark all
+		 * subplans as valid; they must also all be initialized.
+		 */
+		Assert(nplans > 0);
+		appendstate->as_valid_subplans = validsubplans =
+			bms_add_range(NULL, 0, nplans - 1);
+		appendstate->as_prune_state = NULL;
+	}
+
+	/*
+	 * Initialize result tuple type and slot.
+	 */
+	ExecInitResultTupleSlotTL(&appendstate->ps, &TTSOpsVirtual);
+
+	/* node returns slots from each of its subnodes, therefore not fixed */
+	appendstate->ps.resultopsset = true;
+	appendstate->ps.resultopsfixed = false;
+
+	appendplanstates = (PlanState **) palloc(nplans *
+											 sizeof(PlanState *));
+
+	/*
+	 * call ExecInitNode on each of the valid plans to be executed and save
+	 * the results into the appendplanstates array.
+	 *
+	 * While at it, find out the first valid partial plan.
+	 */
+	j = 0;
+	asyncplans = NULL;
+	nasyncplans = 0;
+	firstvalid = nplans;
+	i = -1;
+	while ((i = bms_next_member(validsubplans, i)) >= 0)
+	{
+		Plan	   *initNode = (Plan *) list_nth(node->appendplans, i);
+
+		/*
+		 * Record async subplans.  When executing EvalPlanQual, we treat them
+		 * as sync ones; don't do this when initializing an EvalPlanQual plan
+		 * tree.
+		 */
+		if (initNode->async_capable && estate->es_epq_active == NULL)
+		{
+			asyncplans = bms_add_member(asyncplans, j);
+			nasyncplans++;
+		}
+
+		/*
+		 * Record the lowest appendplans index which is a valid partial plan.
+		 */
+		if (i >= node->first_partial_plan && j < firstvalid)
+			firstvalid = j;
+
+		appendplanstates[j++] = ExecInitNode(initNode, estate, eflags);
+	}
+
+	appendstate->as_first_partial_plan = firstvalid;
+	appendstate->appendplans = appendplanstates;
+	appendstate->as_nplans = nplans;
+
+	/* Initialize async state */
+	appendstate->as_asyncplans = asyncplans;
+	appendstate->as_nasyncplans = nasyncplans;
+	appendstate->as_asyncrequests = NULL;
+	appendstate->as_asyncresults = NULL;
+	appendstate->as_nasyncresults = 0;
+	appendstate->as_nasyncremain = 0;
+	appendstate->as_needrequest = NULL;
+	appendstate->as_eventset = NULL;
+	appendstate->as_valid_asyncplans = NULL;
+
+	if (nasyncplans > 0)
+	{
+		appendstate->as_asyncrequests = (AsyncRequest **)
+			palloc0(nplans * sizeof(AsyncRequest *));
+
+		i = -1;
+		while ((i = bms_next_member(asyncplans, i)) >= 0)
+		{
+			AsyncRequest *areq;
+
+			areq = palloc(sizeof(AsyncRequest));
+			areq->requestor = (PlanState *) appendstate;
+			areq->requestee = appendplanstates[i];
+			areq->request_index = i;
+			areq->callback_pending = false;
+			areq->request_complete = false;
+			areq->result = NULL;
+
+			appendstate->as_asyncrequests[i] = areq;
+		}
+
+		appendstate->as_asyncresults = (TupleTableSlot **)
+			palloc0(nasyncplans * sizeof(TupleTableSlot *));
+
+		if (appendstate->as_valid_subplans != NULL)
+			classify_matching_subplans(appendstate);
+	}
+
+	/*
+	 * Miscellaneous initialization
+	 */
+
+	appendstate->ps.ps_ProjInfo = NULL;
+
+	/* For parallel query, this will be overridden later. */
+	appendstate->choose_next_subplan = choose_next_subplan_locally;
+
+	return appendstate;
+}
+
+/* ----------------------------------------------------------------
+ *	   ExecAppend
+ *
+ *		Handles iteration over multiple subplans.
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+ExecAppend(PlanState *pstate)
+{
+	AppendState *node = castNode(AppendState, pstate);
+	TupleTableSlot *result;
+
+	/*
+	 * If this is the first call after Init or ReScan, we need to do the
+	 * initialization work.
+	 */
+	if (!node->as_begun)
+	{
+		Assert(node->as_whichplan == INVALID_SUBPLAN_INDEX);
+		Assert(!node->as_syncdone);
+
+		/* Nothing to do if there are no subplans */
+		if (node->as_nplans == 0)
+			return ExecClearTuple(node->ps.ps_ResultTupleSlot);
+
+		/* If there are any async subplans, begin executing them. */
+		if (node->as_nasyncplans > 0)
+			ExecAppendAsyncBegin(node);
+
+		/*
+		 * If no sync subplan has been chosen, we must choose one before
+		 * proceeding.
+		 */
+		if (!node->choose_next_subplan(node) && node->as_nasyncremain == 0)
+			return ExecClearTuple(node->ps.ps_ResultTupleSlot);
+
+		Assert(node->as_syncdone ||
+			   (node->as_whichplan >= 0 &&
+				node->as_whichplan < node->as_nplans));
+
+		/* And we're initialized. */
+		node->as_begun = true;
+	}
+
+	for (;;)
+	{
+		PlanState  *subnode;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * try to get a tuple from an async subplan if any
+		 */
+		if (node->as_syncdone || !bms_is_empty(node->as_needrequest))
+		{
+			if (ExecAppendAsyncGetNext(node, &result))
+				return result;
+			Assert(!node->as_syncdone);
+			Assert(bms_is_empty(node->as_needrequest));
+		}
+
+		/*
+		 * figure out which sync subplan we are currently processing
+		 */
+		Assert(node->as_whichplan >= 0 && node->as_whichplan < node->as_nplans);
+		subnode = node->appendplans[node->as_whichplan];
+
+		/*
+		 * get a tuple from the subplan
+		 */
+		result = ExecProcNode(subnode);
+
+		if (!TupIsNull(result))
+		{
+			/*
+			 * If the subplan gave us something then return it as-is. We do
+			 * NOT make use of the result slot that was set up in
+			 * ExecInitAppend; there's no need for it.
+			 */
+			return result;
+		}
+
+		/*
+		 * wait or poll for async events if any. We do this before checking
+		 * for the end of iteration, because it might drain the remaining
+		 * async subplans.
+		 */
+		if (node->as_nasyncremain > 0)
+			ExecAppendAsyncEventWait(node);
+
+		/* choose new sync subplan; if no sync/async subplans, we're done */
+		if (!node->choose_next_subplan(node) && node->as_nasyncremain == 0)
+			return ExecClearTuple(node->ps.ps_ResultTupleSlot);
+	}
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndAppend
+ *
+ *		Shuts down the subscans of the append node.
+ *
+ *		Returns nothing of interest.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndAppend(AppendState *node)
+{
+	PlanState **appendplans;
+	int			nplans;
+	int			i;
+
+	/*
+	 * get information from the node
+	 */
+	appendplans = node->appendplans;
+	nplans = node->as_nplans;
+
+	/*
+	 * shut down each of the subscans
+	 */
+	for (i = 0; i < nplans; i++)
+		ExecEndNode(appendplans[i]);
+}
+
+void
+ExecReScanAppend(AppendState *node)
+{
+	int			nasyncplans = node->as_nasyncplans;
+	int			i;
+
+	/*
+	 * If any PARAM_EXEC Params used in pruning expressions have changed, then
+	 * we'd better unset the valid subplans so that they are reselected for
+	 * the new parameter values.
+	 */
+	if (node->as_prune_state &&
+		bms_overlap(node->ps.chgParam,
+					node->as_prune_state->execparamids))
+	{
+		bms_free(node->as_valid_subplans);
+		node->as_valid_subplans = NULL;
+		if (nasyncplans > 0)
+		{
+			bms_free(node->as_valid_asyncplans);
+			node->as_valid_asyncplans = NULL;
+		}
+	}
+
+	for (i = 0; i < node->as_nplans; i++)
+	{
+		PlanState  *subnode = node->appendplans[i];
+
+		/*
+		 * ExecReScan doesn't know about my subplans, so I have to do
+		 * changed-parameter signaling myself.
+		 */
+		if (node->ps.chgParam != NULL)
+			UpdateChangedParamSet(subnode, node->ps.chgParam);
+
+		/*
+		 * If chgParam of subnode is not null then plan will be re-scanned by
+		 * first ExecProcNode or by first ExecAsyncRequest.
+		 */
+		if (subnode->chgParam == NULL)
+			ExecReScan(subnode);
+	}
+
+	/* Reset async state */
+	if (nasyncplans > 0)
+	{
+		i = -1;
+		while ((i = bms_next_member(node->as_asyncplans, i)) >= 0)
+		{
+			AsyncRequest *areq = node->as_asyncrequests[i];
+
+			areq->callback_pending = false;
+			areq->request_complete = false;
+			areq->result = NULL;
+		}
+
+		node->as_nasyncresults = 0;
+		node->as_nasyncremain = 0;
+		bms_free(node->as_needrequest);
+		node->as_needrequest = NULL;
+	}
+
+	/* Let choose_next_subplan_* function handle setting the first subplan */
+	node->as_whichplan = INVALID_SUBPLAN_INDEX;
+	node->as_syncdone = false;
+	node->as_begun = false;
+}
+
+/* ----------------------------------------------------------------
+ *						Parallel Append Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecAppendEstimate
+ *
+ *		Compute the amount of space we'll need in the parallel
+ *		query DSM, and inform pcxt->estimator about our needs.
+ * ----------------------------------------------------------------
+ */
+void
+ExecAppendEstimate(AppendState *node,
+				   ParallelContext *pcxt)
+{
+	node->pstate_len =
+		add_size(offsetof(ParallelAppendState, pa_finished),
+				 sizeof(bool) * node->as_nplans);
+
+	shm_toc_estimate_chunk(&pcxt->estimator, node->pstate_len);
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecAppendInitializeDSM
+ *
+ *		Set up shared state for Parallel Append.
+ * ----------------------------------------------------------------
+ */
+void
+ExecAppendInitializeDSM(AppendState *node,
+						ParallelContext *pcxt)
+{
+	ParallelAppendState *pstate;
+
+	pstate = shm_toc_allocate(pcxt->toc, node->pstate_len);
+	memset(pstate, 0, node->pstate_len);
+	LWLockInitialize(&pstate->pa_lock, LWTRANCHE_PARALLEL_APPEND);
+	shm_toc_insert(pcxt->toc, node->ps.plan->plan_node_id, pstate);
+
+	node->as_pstate = pstate;
+	node->choose_next_subplan = choose_next_subplan_for_leader;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecAppendReInitializeDSM
+ *
+ *		Reset shared state before beginning a fresh scan.
+ * ----------------------------------------------------------------
+ */
+void
+ExecAppendReInitializeDSM(AppendState *node, ParallelContext *pcxt)
+{
+	ParallelAppendState *pstate = node->as_pstate;
+
+	pstate->pa_next_plan = 0;
+	memset(pstate->pa_finished, 0, sizeof(bool) * node->as_nplans);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecAppendInitializeWorker
+ *
+ *		Copy relevant information from TOC into planstate, and initialize
+ *		whatever is required to choose and execute the optimal subplan.
+ * ----------------------------------------------------------------
+ */
+void
+ExecAppendInitializeWorker(AppendState *node, ParallelWorkerContext *pwcxt)
+{
+	node->as_pstate = shm_toc_lookup(pwcxt->toc, node->ps.plan->plan_node_id, false);
+	node->choose_next_subplan = choose_next_subplan_for_worker;
+}
+
+/* ----------------------------------------------------------------
+ *		choose_next_subplan_locally
+ *
+ *		Choose next sync subplan for a non-parallel-aware Append,
+ *		returning false if there are no more.
+ * ----------------------------------------------------------------
+ */
+static bool
+choose_next_subplan_locally(AppendState *node)
+{
+	int			whichplan = node->as_whichplan;
+	int			nextplan;
+
+	/* We should never be called when there are no subplans */
+	Assert(node->as_nplans > 0);
+
+	/* Nothing to do if syncdone */
+	if (node->as_syncdone)
+		return false;
+
+	/*
+	 * If first call then have the bms member function choose the first valid
+	 * sync subplan by initializing whichplan to -1.  If there happen to be no
+	 * valid sync subplans then the bms member function will handle that by
+	 * returning a negative number which will allow us to exit returning a
+	 * false value.
+	 */
+	if (whichplan == INVALID_SUBPLAN_INDEX)
+	{
+		if (node->as_nasyncplans > 0)
+		{
+			/* We'd have filled as_valid_subplans already */
+			Assert(node->as_valid_subplans);
+		}
+		else if (node->as_valid_subplans == NULL)
+			node->as_valid_subplans =
+				ExecFindMatchingSubPlans(node->as_prune_state);
+
+		whichplan = -1;
+	}
+
+	/* Ensure whichplan is within the expected range */
+	Assert(whichplan >= -1 && whichplan <= node->as_nplans);
+
+	if (ScanDirectionIsForward(node->ps.state->es_direction))
+		nextplan = bms_next_member(node->as_valid_subplans, whichplan);
+	else
+		nextplan = bms_prev_member(node->as_valid_subplans, whichplan);
+
+	if (nextplan < 0)
+	{
+		/* Set as_syncdone if in async mode */
+		if (node->as_nasyncplans > 0)
+			node->as_syncdone = true;
+		return false;
+	}
+
+	node->as_whichplan = nextplan;
+
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		choose_next_subplan_for_leader
+ *
+ *      Try to pick a plan which doesn't commit us to doing much
+ *      work locally, so that as much work as possible is done in
+ *      the workers.  Cheapest subplans are at the end.
+ * ----------------------------------------------------------------
+ */
+static bool
+choose_next_subplan_for_leader(AppendState *node)
+{
+	ParallelAppendState *pstate = node->as_pstate;
+
+	/* Backward scan is not supported by parallel-aware plans */
+	Assert(ScanDirectionIsForward(node->ps.state->es_direction));
+
+	/* We should never be called when there are no subplans */
+	Assert(node->as_nplans > 0);
+
+	LWLockAcquire(&pstate->pa_lock, LW_EXCLUSIVE);
+
+	if (node->as_whichplan != INVALID_SUBPLAN_INDEX)
+	{
+		/* Mark just-completed subplan as finished. */
+		node->as_pstate->pa_finished[node->as_whichplan] = true;
+	}
+	else
+	{
+		/* Start with last subplan. */
+		node->as_whichplan = node->as_nplans - 1;
+
+		/*
+		 * If we've yet to determine the valid subplans then do so now.  If
+		 * run-time pruning is disabled then the valid subplans will always be
+		 * set to all subplans.
+		 */
+		if (node->as_valid_subplans == NULL)
+		{
+			node->as_valid_subplans =
+				ExecFindMatchingSubPlans(node->as_prune_state);
+
+			/*
+			 * Mark each invalid plan as finished to allow the loop below to
+			 * select the first valid subplan.
+			 */
+			mark_invalid_subplans_as_finished(node);
+		}
+	}
+
+	/* Loop until we find a subplan to execute. */
+	while (pstate->pa_finished[node->as_whichplan])
+	{
+		if (node->as_whichplan == 0)
+		{
+			pstate->pa_next_plan = INVALID_SUBPLAN_INDEX;
+			node->as_whichplan = INVALID_SUBPLAN_INDEX;
+			LWLockRelease(&pstate->pa_lock);
+			return false;
+		}
+
+		/*
+		 * We needn't pay attention to as_valid_subplans here as all invalid
+		 * plans have been marked as finished.
+		 */
+		node->as_whichplan--;
+	}
+
+	/* If non-partial, immediately mark as finished. */
+	if (node->as_whichplan < node->as_first_partial_plan)
+		node->as_pstate->pa_finished[node->as_whichplan] = true;
+
+	LWLockRelease(&pstate->pa_lock);
+
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		choose_next_subplan_for_worker
+ *
+ *		Choose next subplan for a parallel-aware Append, returning
+ *		false if there are no more.
+ *
+ *		We start from the first plan and advance through the list;
+ *		when we get back to the end, we loop back to the first
+ *		partial plan.  This assigns the non-partial plans first in
+ *		order of descending cost and then spreads out the workers
+ *		as evenly as possible across the remaining partial plans.
+ * ----------------------------------------------------------------
+ */
+static bool
+choose_next_subplan_for_worker(AppendState *node)
+{
+	ParallelAppendState *pstate = node->as_pstate;
+
+	/* Backward scan is not supported by parallel-aware plans */
+	Assert(ScanDirectionIsForward(node->ps.state->es_direction));
+
+	/* We should never be called when there are no subplans */
+	Assert(node->as_nplans > 0);
+
+	LWLockAcquire(&pstate->pa_lock, LW_EXCLUSIVE);
+
+	/* Mark just-completed subplan as finished. */
+	if (node->as_whichplan != INVALID_SUBPLAN_INDEX)
+		node->as_pstate->pa_finished[node->as_whichplan] = true;
+
+	/*
+	 * If we've yet to determine the valid subplans then do so now.  If
+	 * run-time pruning is disabled then the valid subplans will always be set
+	 * to all subplans.
+	 */
+	else if (node->as_valid_subplans == NULL)
+	{
+		node->as_valid_subplans =
+			ExecFindMatchingSubPlans(node->as_prune_state);
+		mark_invalid_subplans_as_finished(node);
+	}
+
+	/* If all the plans are already done, we have nothing to do */
+	if (pstate->pa_next_plan == INVALID_SUBPLAN_INDEX)
+	{
+		LWLockRelease(&pstate->pa_lock);
+		return false;
+	}
+
+	/* Save the plan from which we are starting the search. */
+	node->as_whichplan = pstate->pa_next_plan;
+
+	/* Loop until we find a valid subplan to execute. */
+	while (pstate->pa_finished[pstate->pa_next_plan])
+	{
+		int			nextplan;
+
+		nextplan = bms_next_member(node->as_valid_subplans,
+								   pstate->pa_next_plan);
+		if (nextplan >= 0)
+		{
+			/* Advance to the next valid plan. */
+			pstate->pa_next_plan = nextplan;
+		}
+		else if (node->as_whichplan > node->as_first_partial_plan)
+		{
+			/*
+			 * Try looping back to the first valid partial plan, if there is
+			 * one.  If there isn't, arrange to bail out below.
+			 */
+			nextplan = bms_next_member(node->as_valid_subplans,
+									   node->as_first_partial_plan - 1);
+			pstate->pa_next_plan =
+				nextplan < 0 ? node->as_whichplan : nextplan;
+		}
+		else
+		{
+			/*
+			 * At last plan, and either there are no partial plans or we've
+			 * tried them all.  Arrange to bail out.
+			 */
+			pstate->pa_next_plan = node->as_whichplan;
+		}
+
+		if (pstate->pa_next_plan == node->as_whichplan)
+		{
+			/* We've tried everything! */
+			pstate->pa_next_plan = INVALID_SUBPLAN_INDEX;
+			LWLockRelease(&pstate->pa_lock);
+			return false;
+		}
+	}
+
+	/* Pick the plan we found, and advance pa_next_plan one more time. */
+	node->as_whichplan = pstate->pa_next_plan;
+	pstate->pa_next_plan = bms_next_member(node->as_valid_subplans,
+										   pstate->pa_next_plan);
+
+	/*
+	 * If there are no more valid plans then try setting the next plan to the
+	 * first valid partial plan.
+	 */
+	if (pstate->pa_next_plan < 0)
+	{
+		int			nextplan = bms_next_member(node->as_valid_subplans,
+											   node->as_first_partial_plan - 1);
+
+		if (nextplan >= 0)
+			pstate->pa_next_plan = nextplan;
+		else
+		{
+			/*
+			 * There are no valid partial plans, and we already chose the last
+			 * non-partial plan; so flag that there's nothing more for our
+			 * fellow workers to do.
+			 */
+			pstate->pa_next_plan = INVALID_SUBPLAN_INDEX;
+		}
+	}
+
+	/* If non-partial, immediately mark as finished. */
+	if (node->as_whichplan < node->as_first_partial_plan)
+		node->as_pstate->pa_finished[node->as_whichplan] = true;
+
+	LWLockRelease(&pstate->pa_lock);
+
+	return true;
+}
+
+/*
+ * mark_invalid_subplans_as_finished
+ *		Marks the ParallelAppendState's pa_finished as true for each invalid
+ *		subplan.
+ *
+ * This function should only be called for parallel Append with run-time
+ * pruning enabled.
+ */
+static void
+mark_invalid_subplans_as_finished(AppendState *node)
+{
+	int			i;
+
+	/* Only valid to call this while in parallel Append mode */
+	Assert(node->as_pstate);
+
+	/* Shouldn't have been called when run-time pruning is not enabled */
+	Assert(node->as_prune_state);
+
+	/* Nothing to do if all plans are valid */
+	if (bms_num_members(node->as_valid_subplans) == node->as_nplans)
+		return;
+
+	/* Mark all non-valid plans as finished */
+	for (i = 0; i < node->as_nplans; i++)
+	{
+		if (!bms_is_member(i, node->as_valid_subplans))
+			node->as_pstate->pa_finished[i] = true;
+	}
+}
+
+/* ----------------------------------------------------------------
+ *						Asynchronous Append Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecAppendAsyncBegin
+ *
+ *		Begin executing designed async-capable subplans.
+ * ----------------------------------------------------------------
+ */
+static void
+ExecAppendAsyncBegin(AppendState *node)
+{
+	int			i;
+
+	/* Backward scan is not supported by async-aware Appends. */
+	Assert(ScanDirectionIsForward(node->ps.state->es_direction));
+
+	/* We should never be called when there are no subplans */
+	Assert(node->as_nplans > 0);
+
+	/* We should never be called when there are no async subplans. */
+	Assert(node->as_nasyncplans > 0);
+
+	/* If we've yet to determine the valid subplans then do so now. */
+	if (node->as_valid_subplans == NULL)
+	{
+		node->as_valid_subplans =
+			ExecFindMatchingSubPlans(node->as_prune_state);
+
+		classify_matching_subplans(node);
+	}
+
+	/* Initialize state variables. */
+	node->as_syncdone = bms_is_empty(node->as_valid_subplans);
+	node->as_nasyncremain = bms_num_members(node->as_valid_asyncplans);
+
+	/* Nothing to do if there are no valid async subplans. */
+	if (node->as_nasyncremain == 0)
+		return;
+
+	/* Make a request for each of the valid async subplans. */
+	i = -1;
+	while ((i = bms_next_member(node->as_valid_asyncplans, i)) >= 0)
+	{
+		AsyncRequest *areq = node->as_asyncrequests[i];
+
+		Assert(areq->request_index == i);
+		Assert(!areq->callback_pending);
+
+		/* Do the actual work. */
+		ExecAsyncRequest(areq);
+	}
+}
+
+/* ----------------------------------------------------------------
+ *		ExecAppendAsyncGetNext
+ *
+ *		Get the next tuple from any of the asynchronous subplans.
+ * ----------------------------------------------------------------
+ */
+static bool
+ExecAppendAsyncGetNext(AppendState *node, TupleTableSlot **result)
+{
+	*result = NULL;
+
+	/* We should never be called when there are no valid async subplans. */
+	Assert(node->as_nasyncremain > 0);
+
+	/* Request a tuple asynchronously. */
+	if (ExecAppendAsyncRequest(node, result))
+		return true;
+
+	while (node->as_nasyncremain > 0)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		/* Wait or poll for async events. */
+		ExecAppendAsyncEventWait(node);
+
+		/* Request a tuple asynchronously. */
+		if (ExecAppendAsyncRequest(node, result))
+			return true;
+
+		/* Break from loop if there's any sync subplan that isn't complete. */
+		if (!node->as_syncdone)
+			break;
+	}
+
+	/*
+	 * If all sync subplans are complete, we're totally done scanning the
+	 * given node.  Otherwise, we're done with the asynchronous stuff but must
+	 * continue scanning the sync subplans.
+	 */
+	if (node->as_syncdone)
+	{
+		Assert(node->as_nasyncremain == 0);
+		*result = ExecClearTuple(node->ps.ps_ResultTupleSlot);
+		return true;
+	}
+
+	return false;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecAppendAsyncRequest
+ *
+ *		Request a tuple asynchronously.
+ * ----------------------------------------------------------------
+ */
+static bool
+ExecAppendAsyncRequest(AppendState *node, TupleTableSlot **result)
+{
+	Bitmapset  *needrequest;
+	int			i;
+
+	/* Nothing to do if there are no async subplans needing a new request. */
+	if (bms_is_empty(node->as_needrequest))
+	{
+		Assert(node->as_nasyncresults == 0);
+		return false;
+	}
+
+	/*
+	 * If there are any asynchronously-generated results that have not yet
+	 * been returned, we have nothing to do; just return one of them.
+	 */
+	if (node->as_nasyncresults > 0)
+	{
+		--node->as_nasyncresults;
+		*result = node->as_asyncresults[node->as_nasyncresults];
+		return true;
+	}
+
+	/* Make a new request for each of the async subplans that need it. */
+	needrequest = node->as_needrequest;
+	node->as_needrequest = NULL;
+	i = -1;
+	while ((i = bms_next_member(needrequest, i)) >= 0)
+	{
+		AsyncRequest *areq = node->as_asyncrequests[i];
+
+		/* Do the actual work. */
+		ExecAsyncRequest(areq);
+	}
+	bms_free(needrequest);
+
+	/* Return one of the asynchronously-generated results if any. */
+	if (node->as_nasyncresults > 0)
+	{
+		--node->as_nasyncresults;
+		*result = node->as_asyncresults[node->as_nasyncresults];
+		return true;
+	}
+
+	return false;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecAppendAsyncEventWait
+ *
+ *		Wait or poll for file descriptor events and fire callbacks.
+ * ----------------------------------------------------------------
+ */
+static void
+ExecAppendAsyncEventWait(AppendState *node)
+{
+	int			nevents = node->as_nasyncplans + 1;
+	long		timeout = node->as_syncdone ? -1 : 0;
+	WaitEvent	occurred_event[EVENT_BUFFER_SIZE];
+	int			noccurred;
+	int			i;
+
+	/* We should never be called when there are no valid async subplans. */
+	Assert(node->as_nasyncremain > 0);
+
+	node->as_eventset = CreateWaitEventSet(CurrentMemoryContext, nevents);
+	AddWaitEventToSet(node->as_eventset, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET,
+					  NULL, NULL);
+
+	/* Give each waiting subplan a chance to add an event. */
+	i = -1;
+	while ((i = bms_next_member(node->as_asyncplans, i)) >= 0)
+	{
+		AsyncRequest *areq = node->as_asyncrequests[i];
+
+		if (areq->callback_pending)
+			ExecAsyncConfigureWait(areq);
+	}
+
+	/*
+	 * No need for further processing if there are no configured events other
+	 * than the postmaster death event.
+	 */
+	if (GetNumRegisteredWaitEvents(node->as_eventset) == 1)
+	{
+		FreeWaitEventSet(node->as_eventset);
+		node->as_eventset = NULL;
+		return;
+	}
+
+	/* We wait on at most EVENT_BUFFER_SIZE events. */
+	if (nevents > EVENT_BUFFER_SIZE)
+		nevents = EVENT_BUFFER_SIZE;
+
+	/*
+	 * If the timeout is -1, wait until at least one event occurs.  If the
+	 * timeout is 0, poll for events, but do not wait at all.
+	 */
+	noccurred = WaitEventSetWait(node->as_eventset, timeout, occurred_event,
+								 nevents, WAIT_EVENT_APPEND_READY);
+	FreeWaitEventSet(node->as_eventset);
+	node->as_eventset = NULL;
+	if (noccurred == 0)
+		return;
+
+	/* Deliver notifications. */
+	for (i = 0; i < noccurred; i++)
+	{
+		WaitEvent  *w = &occurred_event[i];
+
+		/*
+		 * Each waiting subplan should have registered its wait event with
+		 * user_data pointing back to its AsyncRequest.
+		 */
+		if ((w->events & WL_SOCKET_READABLE) != 0)
+		{
+			AsyncRequest *areq = (AsyncRequest *) w->user_data;
+
+			if (areq->callback_pending)
+			{
+				/*
+				 * Mark it as no longer needing a callback.  We must do this
+				 * before dispatching the callback in case the callback resets
+				 * the flag.
+				 */
+				areq->callback_pending = false;
+
+				/* Do the actual work. */
+				ExecAsyncNotify(areq);
+			}
+		}
+	}
+}
+
+/* ----------------------------------------------------------------
+ *		ExecAsyncAppendResponse
+ *
+ *		Receive a response from an asynchronous request we made.
+ * ----------------------------------------------------------------
+ */
+void
+ExecAsyncAppendResponse(AsyncRequest *areq)
+{
+	AppendState *node = (AppendState *) areq->requestor;
+	TupleTableSlot *slot = areq->result;
+
+	/* The result should be a TupleTableSlot or NULL. */
+	Assert(slot == NULL || IsA(slot, TupleTableSlot));
+
+	/* Nothing to do if the request is pending. */
+	if (!areq->request_complete)
+	{
+		/* The request would have been pending for a callback. */
+		Assert(areq->callback_pending);
+		return;
+	}
+
+	/* If the result is NULL or an empty slot, there's nothing more to do. */
+	if (TupIsNull(slot))
+	{
+		/* The ending subplan wouldn't have been pending for a callback. */
+		Assert(!areq->callback_pending);
+		--node->as_nasyncremain;
+		return;
+	}
+
+	/* Save result so we can return it. */
+	Assert(node->as_nasyncresults < node->as_nasyncplans);
+	node->as_asyncresults[node->as_nasyncresults++] = slot;
+
+	/*
+	 * Mark the subplan that returned a result as ready for a new request.  We
+	 * don't launch another one here immediately because it might complete.
+	 */
+	node->as_needrequest = bms_add_member(node->as_needrequest,
+										  areq->request_index);
+}
+
+/* ----------------------------------------------------------------
+ *		classify_matching_subplans
+ *
+ *		Classify the node's as_valid_subplans into sync ones and
+ *		async ones, adjust it to contain sync ones only, and save
+ *		async ones in the node's as_valid_asyncplans.
+ * ----------------------------------------------------------------
+ */
+static void
+classify_matching_subplans(AppendState *node)
+{
+	Bitmapset  *valid_asyncplans;
+
+	Assert(node->as_valid_asyncplans == NULL);
+
+	/* Nothing to do if there are no valid subplans. */
+	if (bms_is_empty(node->as_valid_subplans))
+	{
+		node->as_syncdone = true;
+		node->as_nasyncremain = 0;
+		return;
+	}
+
+	/* Nothing to do if there are no valid async subplans. */
+	if (!bms_overlap(node->as_valid_subplans, node->as_asyncplans))
+	{
+		node->as_nasyncremain = 0;
+		return;
+	}
+
+	/* Get valid async subplans. */
+	valid_asyncplans = bms_copy(node->as_asyncplans);
+	valid_asyncplans = bms_int_members(valid_asyncplans,
+									   node->as_valid_subplans);
+
+	/* Adjust the valid subplans to contain sync subplans only. */
+	node->as_valid_subplans = bms_del_members(node->as_valid_subplans,
+											  valid_asyncplans);
+
+	/* Save valid async subplans. */
+	node->as_valid_asyncplans = valid_asyncplans;
+}