Adding upstream version 14.5.upstream/14.5upstream

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

1 files changed, 1498 insertions, 0 deletions

diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c
new file mode 100644
index 0000000..f8a4a40
--- /dev/null
+++ b/src/backend/executor/execParallel.c
@@ -0,0 +1,1498 @@
+/*-------------------------------------------------------------------------
+ *
+ * execParallel.c
+ *	  Support routines for parallel execution.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * This file contains routines that are intended to support setting up,
+ * using, and tearing down a ParallelContext from within the PostgreSQL
+ * executor.  The ParallelContext machinery will handle starting the
+ * workers and ensuring that their state generally matches that of the
+ * leader; see src/backend/access/transam/README.parallel for details.
+ * However, we must save and restore relevant executor state, such as
+ * any ParamListInfo associated with the query, buffer/WAL usage info, and
+ * the actual plan to be passed down to the worker.
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/execParallel.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "executor/execParallel.h"
+#include "executor/executor.h"
+#include "executor/nodeAgg.h"
+#include "executor/nodeAppend.h"
+#include "executor/nodeBitmapHeapscan.h"
+#include "executor/nodeCustom.h"
+#include "executor/nodeForeignscan.h"
+#include "executor/nodeHash.h"
+#include "executor/nodeHashjoin.h"
+#include "executor/nodeIncrementalSort.h"
+#include "executor/nodeIndexonlyscan.h"
+#include "executor/nodeIndexscan.h"
+#include "executor/nodeMemoize.h"
+#include "executor/nodeSeqscan.h"
+#include "executor/nodeSort.h"
+#include "executor/nodeSubplan.h"
+#include "executor/tqueue.h"
+#include "jit/jit.h"
+#include "nodes/nodeFuncs.h"
+#include "pgstat.h"
+#include "storage/spin.h"
+#include "tcop/tcopprot.h"
+#include "utils/datum.h"
+#include "utils/dsa.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/snapmgr.h"
+
+/*
+ * Magic numbers for parallel executor communication.  We use constants
+ * greater than any 32-bit integer here so that values < 2^32 can be used
+ * by individual parallel nodes to store their own state.
+ */
+#define PARALLEL_KEY_EXECUTOR_FIXED		UINT64CONST(0xE000000000000001)
+#define PARALLEL_KEY_PLANNEDSTMT		UINT64CONST(0xE000000000000002)
+#define PARALLEL_KEY_PARAMLISTINFO		UINT64CONST(0xE000000000000003)
+#define PARALLEL_KEY_BUFFER_USAGE		UINT64CONST(0xE000000000000004)
+#define PARALLEL_KEY_TUPLE_QUEUE		UINT64CONST(0xE000000000000005)
+#define PARALLEL_KEY_INSTRUMENTATION	UINT64CONST(0xE000000000000006)
+#define PARALLEL_KEY_DSA				UINT64CONST(0xE000000000000007)
+#define PARALLEL_KEY_QUERY_TEXT		UINT64CONST(0xE000000000000008)
+#define PARALLEL_KEY_JIT_INSTRUMENTATION UINT64CONST(0xE000000000000009)
+#define PARALLEL_KEY_WAL_USAGE			UINT64CONST(0xE00000000000000A)
+
+#define PARALLEL_TUPLE_QUEUE_SIZE		65536
+
+/*
+ * Fixed-size random stuff that we need to pass to parallel workers.
+ */
+typedef struct FixedParallelExecutorState
+{
+	int64		tuples_needed;	/* tuple bound, see ExecSetTupleBound */
+	dsa_pointer param_exec;
+	int			eflags;
+	int			jit_flags;
+} FixedParallelExecutorState;
+
+/*
+ * DSM structure for accumulating per-PlanState instrumentation.
+ *
+ * instrument_options: Same meaning here as in instrument.c.
+ *
+ * instrument_offset: Offset, relative to the start of this structure,
+ * of the first Instrumentation object.  This will depend on the length of
+ * the plan_node_id array.
+ *
+ * num_workers: Number of workers.
+ *
+ * num_plan_nodes: Number of plan nodes.
+ *
+ * plan_node_id: Array of plan nodes for which we are gathering instrumentation
+ * from parallel workers.  The length of this array is given by num_plan_nodes.
+ */
+struct SharedExecutorInstrumentation
+{
+	int			instrument_options;
+	int			instrument_offset;
+	int			num_workers;
+	int			num_plan_nodes;
+	int			plan_node_id[FLEXIBLE_ARRAY_MEMBER];
+	/* array of num_plan_nodes * num_workers Instrumentation objects follows */
+};
+#define GetInstrumentationArray(sei) \
+	(AssertVariableIsOfTypeMacro(sei, SharedExecutorInstrumentation *), \
+	 (Instrumentation *) (((char *) sei) + sei->instrument_offset))
+
+/* Context object for ExecParallelEstimate. */
+typedef struct ExecParallelEstimateContext
+{
+	ParallelContext *pcxt;
+	int			nnodes;
+} ExecParallelEstimateContext;
+
+/* Context object for ExecParallelInitializeDSM. */
+typedef struct ExecParallelInitializeDSMContext
+{
+	ParallelContext *pcxt;
+	SharedExecutorInstrumentation *instrumentation;
+	int			nnodes;
+} ExecParallelInitializeDSMContext;
+
+/* Helper functions that run in the parallel leader. */
+static char *ExecSerializePlan(Plan *plan, EState *estate);
+static bool ExecParallelEstimate(PlanState *node,
+								 ExecParallelEstimateContext *e);
+static bool ExecParallelInitializeDSM(PlanState *node,
+									  ExecParallelInitializeDSMContext *d);
+static shm_mq_handle **ExecParallelSetupTupleQueues(ParallelContext *pcxt,
+													bool reinitialize);
+static bool ExecParallelReInitializeDSM(PlanState *planstate,
+										ParallelContext *pcxt);
+static bool ExecParallelRetrieveInstrumentation(PlanState *planstate,
+												SharedExecutorInstrumentation *instrumentation);
+
+/* Helper function that runs in the parallel worker. */
+static DestReceiver *ExecParallelGetReceiver(dsm_segment *seg, shm_toc *toc);
+
+/*
+ * Create a serialized representation of the plan to be sent to each worker.
+ */
+static char *
+ExecSerializePlan(Plan *plan, EState *estate)
+{
+	PlannedStmt *pstmt;
+	ListCell   *lc;
+
+	/* We can't scribble on the original plan, so make a copy. */
+	plan = copyObject(plan);
+
+	/*
+	 * The worker will start its own copy of the executor, and that copy will
+	 * insert a junk filter if the toplevel node has any resjunk entries. We
+	 * don't want that to happen, because while resjunk columns shouldn't be
+	 * sent back to the user, here the tuples are coming back to another
+	 * backend which may very well need them.  So mutate the target list
+	 * accordingly.  This is sort of a hack; there might be better ways to do
+	 * this...
+	 */
+	foreach(lc, plan->targetlist)
+	{
+		TargetEntry *tle = lfirst_node(TargetEntry, lc);
+
+		tle->resjunk = false;
+	}
+
+	/*
+	 * Create a dummy PlannedStmt.  Most of the fields don't need to be valid
+	 * for our purposes, but the worker will need at least a minimal
+	 * PlannedStmt to start the executor.
+	 */
+	pstmt = makeNode(PlannedStmt);
+	pstmt->commandType = CMD_SELECT;
+	pstmt->queryId = pgstat_get_my_query_id();
+	pstmt->hasReturning = false;
+	pstmt->hasModifyingCTE = false;
+	pstmt->canSetTag = true;
+	pstmt->transientPlan = false;
+	pstmt->dependsOnRole = false;
+	pstmt->parallelModeNeeded = false;
+	pstmt->planTree = plan;
+	pstmt->rtable = estate->es_range_table;
+	pstmt->resultRelations = NIL;
+	pstmt->appendRelations = NIL;
+
+	/*
+	 * Transfer only parallel-safe subplans, leaving a NULL "hole" in the list
+	 * for unsafe ones (so that the list indexes of the safe ones are
+	 * preserved).  This positively ensures that the worker won't try to run,
+	 * or even do ExecInitNode on, an unsafe subplan.  That's important to
+	 * protect, eg, non-parallel-aware FDWs from getting into trouble.
+	 */
+	pstmt->subplans = NIL;
+	foreach(lc, estate->es_plannedstmt->subplans)
+	{
+		Plan	   *subplan = (Plan *) lfirst(lc);
+
+		if (subplan && !subplan->parallel_safe)
+			subplan = NULL;
+		pstmt->subplans = lappend(pstmt->subplans, subplan);
+	}
+
+	pstmt->rewindPlanIDs = NULL;
+	pstmt->rowMarks = NIL;
+	pstmt->relationOids = NIL;
+	pstmt->invalItems = NIL;	/* workers can't replan anyway... */
+	pstmt->paramExecTypes = estate->es_plannedstmt->paramExecTypes;
+	pstmt->utilityStmt = NULL;
+	pstmt->stmt_location = -1;
+	pstmt->stmt_len = -1;
+
+	/* Return serialized copy of our dummy PlannedStmt. */
+	return nodeToString(pstmt);
+}
+
+/*
+ * Parallel-aware plan nodes (and occasionally others) may need some state
+ * which is shared across all parallel workers.  Before we size the DSM, give
+ * them a chance to call shm_toc_estimate_chunk or shm_toc_estimate_keys on
+ * &pcxt->estimator.
+ *
+ * While we're at it, count the number of PlanState nodes in the tree, so
+ * we know how many Instrumentation structures we need.
+ */
+static bool
+ExecParallelEstimate(PlanState *planstate, ExecParallelEstimateContext *e)
+{
+	if (planstate == NULL)
+		return false;
+
+	/* Count this node. */
+	e->nnodes++;
+
+	switch (nodeTag(planstate))
+	{
+		case T_SeqScanState:
+			if (planstate->plan->parallel_aware)
+				ExecSeqScanEstimate((SeqScanState *) planstate,
+									e->pcxt);
+			break;
+		case T_IndexScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexScanEstimate((IndexScanState *) planstate,
+									  e->pcxt);
+			break;
+		case T_IndexOnlyScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexOnlyScanEstimate((IndexOnlyScanState *) planstate,
+										  e->pcxt);
+			break;
+		case T_ForeignScanState:
+			if (planstate->plan->parallel_aware)
+				ExecForeignScanEstimate((ForeignScanState *) planstate,
+										e->pcxt);
+			break;
+		case T_AppendState:
+			if (planstate->plan->parallel_aware)
+				ExecAppendEstimate((AppendState *) planstate,
+								   e->pcxt);
+			break;
+		case T_CustomScanState:
+			if (planstate->plan->parallel_aware)
+				ExecCustomScanEstimate((CustomScanState *) planstate,
+									   e->pcxt);
+			break;
+		case T_BitmapHeapScanState:
+			if (planstate->plan->parallel_aware)
+				ExecBitmapHeapEstimate((BitmapHeapScanState *) planstate,
+									   e->pcxt);
+			break;
+		case T_HashJoinState:
+			if (planstate->plan->parallel_aware)
+				ExecHashJoinEstimate((HashJoinState *) planstate,
+									 e->pcxt);
+			break;
+		case T_HashState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecHashEstimate((HashState *) planstate, e->pcxt);
+			break;
+		case T_SortState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecSortEstimate((SortState *) planstate, e->pcxt);
+			break;
+		case T_IncrementalSortState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecIncrementalSortEstimate((IncrementalSortState *) planstate, e->pcxt);
+			break;
+		case T_AggState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecAggEstimate((AggState *) planstate, e->pcxt);
+			break;
+		case T_MemoizeState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecMemoizeEstimate((MemoizeState *) planstate, e->pcxt);
+			break;
+		default:
+			break;
+	}
+
+	return planstate_tree_walker(planstate, ExecParallelEstimate, e);
+}
+
+/*
+ * Estimate the amount of space required to serialize the indicated parameters.
+ */
+static Size
+EstimateParamExecSpace(EState *estate, Bitmapset *params)
+{
+	int			paramid;
+	Size		sz = sizeof(int);
+
+	paramid = -1;
+	while ((paramid = bms_next_member(params, paramid)) >= 0)
+	{
+		Oid			typeOid;
+		int16		typLen;
+		bool		typByVal;
+		ParamExecData *prm;
+
+		prm = &(estate->es_param_exec_vals[paramid]);
+		typeOid = list_nth_oid(estate->es_plannedstmt->paramExecTypes,
+							   paramid);
+
+		sz = add_size(sz, sizeof(int)); /* space for paramid */
+
+		/* space for datum/isnull */
+		if (OidIsValid(typeOid))
+			get_typlenbyval(typeOid, &typLen, &typByVal);
+		else
+		{
+			/* If no type OID, assume by-value, like copyParamList does. */
+			typLen = sizeof(Datum);
+			typByVal = true;
+		}
+		sz = add_size(sz,
+					  datumEstimateSpace(prm->value, prm->isnull,
+										 typByVal, typLen));
+	}
+	return sz;
+}
+
+/*
+ * Serialize specified PARAM_EXEC parameters.
+ *
+ * We write the number of parameters first, as a 4-byte integer, and then
+ * write details for each parameter in turn.  The details for each parameter
+ * consist of a 4-byte paramid (location of param in execution time internal
+ * parameter array) and then the datum as serialized by datumSerialize().
+ */
+static dsa_pointer
+SerializeParamExecParams(EState *estate, Bitmapset *params, dsa_area *area)
+{
+	Size		size;
+	int			nparams;
+	int			paramid;
+	ParamExecData *prm;
+	dsa_pointer handle;
+	char	   *start_address;
+
+	/* Allocate enough space for the current parameter values. */
+	size = EstimateParamExecSpace(estate, params);
+	handle = dsa_allocate(area, size);
+	start_address = dsa_get_address(area, handle);
+
+	/* First write the number of parameters as a 4-byte integer. */
+	nparams = bms_num_members(params);
+	memcpy(start_address, &nparams, sizeof(int));
+	start_address += sizeof(int);
+
+	/* Write details for each parameter in turn. */
+	paramid = -1;
+	while ((paramid = bms_next_member(params, paramid)) >= 0)
+	{
+		Oid			typeOid;
+		int16		typLen;
+		bool		typByVal;
+
+		prm = &(estate->es_param_exec_vals[paramid]);
+		typeOid = list_nth_oid(estate->es_plannedstmt->paramExecTypes,
+							   paramid);
+
+		/* Write paramid. */
+		memcpy(start_address, &paramid, sizeof(int));
+		start_address += sizeof(int);
+
+		/* Write datum/isnull */
+		if (OidIsValid(typeOid))
+			get_typlenbyval(typeOid, &typLen, &typByVal);
+		else
+		{
+			/* If no type OID, assume by-value, like copyParamList does. */
+			typLen = sizeof(Datum);
+			typByVal = true;
+		}
+		datumSerialize(prm->value, prm->isnull, typByVal, typLen,
+					   &start_address);
+	}
+
+	return handle;
+}
+
+/*
+ * Restore specified PARAM_EXEC parameters.
+ */
+static void
+RestoreParamExecParams(char *start_address, EState *estate)
+{
+	int			nparams;
+	int			i;
+	int			paramid;
+
+	memcpy(&nparams, start_address, sizeof(int));
+	start_address += sizeof(int);
+
+	for (i = 0; i < nparams; i++)
+	{
+		ParamExecData *prm;
+
+		/* Read paramid */
+		memcpy(&paramid, start_address, sizeof(int));
+		start_address += sizeof(int);
+		prm = &(estate->es_param_exec_vals[paramid]);
+
+		/* Read datum/isnull. */
+		prm->value = datumRestore(&start_address, &prm->isnull);
+		prm->execPlan = NULL;
+	}
+}
+
+/*
+ * Initialize the dynamic shared memory segment that will be used to control
+ * parallel execution.
+ */
+static bool
+ExecParallelInitializeDSM(PlanState *planstate,
+						  ExecParallelInitializeDSMContext *d)
+{
+	if (planstate == NULL)
+		return false;
+
+	/* If instrumentation is enabled, initialize slot for this node. */
+	if (d->instrumentation != NULL)
+		d->instrumentation->plan_node_id[d->nnodes] =
+			planstate->plan->plan_node_id;
+
+	/* Count this node. */
+	d->nnodes++;
+
+	/*
+	 * Call initializers for DSM-using plan nodes.
+	 *
+	 * Most plan nodes won't do anything here, but plan nodes that allocated
+	 * DSM may need to initialize shared state in the DSM before parallel
+	 * workers are launched.  They can allocate the space they previously
+	 * estimated using shm_toc_allocate, and add the keys they previously
+	 * estimated using shm_toc_insert, in each case targeting pcxt->toc.
+	 */
+	switch (nodeTag(planstate))
+	{
+		case T_SeqScanState:
+			if (planstate->plan->parallel_aware)
+				ExecSeqScanInitializeDSM((SeqScanState *) planstate,
+										 d->pcxt);
+			break;
+		case T_IndexScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexScanInitializeDSM((IndexScanState *) planstate,
+										   d->pcxt);
+			break;
+		case T_IndexOnlyScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexOnlyScanInitializeDSM((IndexOnlyScanState *) planstate,
+											   d->pcxt);
+			break;
+		case T_ForeignScanState:
+			if (planstate->plan->parallel_aware)
+				ExecForeignScanInitializeDSM((ForeignScanState *) planstate,
+											 d->pcxt);
+			break;
+		case T_AppendState:
+			if (planstate->plan->parallel_aware)
+				ExecAppendInitializeDSM((AppendState *) planstate,
+										d->pcxt);
+			break;
+		case T_CustomScanState:
+			if (planstate->plan->parallel_aware)
+				ExecCustomScanInitializeDSM((CustomScanState *) planstate,
+											d->pcxt);
+			break;
+		case T_BitmapHeapScanState:
+			if (planstate->plan->parallel_aware)
+				ExecBitmapHeapInitializeDSM((BitmapHeapScanState *) planstate,
+											d->pcxt);
+			break;
+		case T_HashJoinState:
+			if (planstate->plan->parallel_aware)
+				ExecHashJoinInitializeDSM((HashJoinState *) planstate,
+										  d->pcxt);
+			break;
+		case T_HashState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecHashInitializeDSM((HashState *) planstate, d->pcxt);
+			break;
+		case T_SortState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecSortInitializeDSM((SortState *) planstate, d->pcxt);
+			break;
+		case T_IncrementalSortState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecIncrementalSortInitializeDSM((IncrementalSortState *) planstate, d->pcxt);
+			break;
+		case T_AggState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecAggInitializeDSM((AggState *) planstate, d->pcxt);
+			break;
+		case T_MemoizeState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecMemoizeInitializeDSM((MemoizeState *) planstate, d->pcxt);
+			break;
+		default:
+			break;
+	}
+
+	return planstate_tree_walker(planstate, ExecParallelInitializeDSM, d);
+}
+
+/*
+ * It sets up the response queues for backend workers to return tuples
+ * to the main backend and start the workers.
+ */
+static shm_mq_handle **
+ExecParallelSetupTupleQueues(ParallelContext *pcxt, bool reinitialize)
+{
+	shm_mq_handle **responseq;
+	char	   *tqueuespace;
+	int			i;
+
+	/* Skip this if no workers. */
+	if (pcxt->nworkers == 0)
+		return NULL;
+
+	/* Allocate memory for shared memory queue handles. */
+	responseq = (shm_mq_handle **)
+		palloc(pcxt->nworkers * sizeof(shm_mq_handle *));
+
+	/*
+	 * If not reinitializing, allocate space from the DSM for the queues;
+	 * otherwise, find the already allocated space.
+	 */
+	if (!reinitialize)
+		tqueuespace =
+			shm_toc_allocate(pcxt->toc,
+							 mul_size(PARALLEL_TUPLE_QUEUE_SIZE,
+									  pcxt->nworkers));
+	else
+		tqueuespace = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_TUPLE_QUEUE, false);
+
+	/* Create the queues, and become the receiver for each. */
+	for (i = 0; i < pcxt->nworkers; ++i)
+	{
+		shm_mq	   *mq;
+
+		mq = shm_mq_create(tqueuespace +
+						   ((Size) i) * PARALLEL_TUPLE_QUEUE_SIZE,
+						   (Size) PARALLEL_TUPLE_QUEUE_SIZE);
+
+		shm_mq_set_receiver(mq, MyProc);
+		responseq[i] = shm_mq_attach(mq, pcxt->seg, NULL);
+	}
+
+	/* Add array of queues to shm_toc, so others can find it. */
+	if (!reinitialize)
+		shm_toc_insert(pcxt->toc, PARALLEL_KEY_TUPLE_QUEUE, tqueuespace);
+
+	/* Return array of handles. */
+	return responseq;
+}
+
+/*
+ * Sets up the required infrastructure for backend workers to perform
+ * execution and return results to the main backend.
+ */
+ParallelExecutorInfo *
+ExecInitParallelPlan(PlanState *planstate, EState *estate,
+					 Bitmapset *sendParams, int nworkers,
+					 int64 tuples_needed)
+{
+	ParallelExecutorInfo *pei;
+	ParallelContext *pcxt;
+	ExecParallelEstimateContext e;
+	ExecParallelInitializeDSMContext d;
+	FixedParallelExecutorState *fpes;
+	char	   *pstmt_data;
+	char	   *pstmt_space;
+	char	   *paramlistinfo_space;
+	BufferUsage *bufusage_space;
+	WalUsage   *walusage_space;
+	SharedExecutorInstrumentation *instrumentation = NULL;
+	SharedJitInstrumentation *jit_instrumentation = NULL;
+	int			pstmt_len;
+	int			paramlistinfo_len;
+	int			instrumentation_len = 0;
+	int			jit_instrumentation_len = 0;
+	int			instrument_offset = 0;
+	Size		dsa_minsize = dsa_minimum_size();
+	char	   *query_string;
+	int			query_len;
+
+	/*
+	 * Force any initplan outputs that we're going to pass to workers to be
+	 * evaluated, if they weren't already.
+	 *
+	 * For simplicity, we use the EState's per-output-tuple ExprContext here.
+	 * That risks intra-query memory leakage, since we might pass through here
+	 * many times before that ExprContext gets reset; but ExecSetParamPlan
+	 * doesn't normally leak any memory in the context (see its comments), so
+	 * it doesn't seem worth complicating this function's API to pass it a
+	 * shorter-lived ExprContext.  This might need to change someday.
+	 */
+	ExecSetParamPlanMulti(sendParams, GetPerTupleExprContext(estate));
+
+	/* Allocate object for return value. */
+	pei = palloc0(sizeof(ParallelExecutorInfo));
+	pei->finished = false;
+	pei->planstate = planstate;
+
+	/* Fix up and serialize plan to be sent to workers. */
+	pstmt_data = ExecSerializePlan(planstate->plan, estate);
+
+	/* Create a parallel context. */
+	pcxt = CreateParallelContext("postgres", "ParallelQueryMain", nworkers);
+	pei->pcxt = pcxt;
+
+	/*
+	 * Before telling the parallel context to create a dynamic shared memory
+	 * segment, we need to figure out how big it should be.  Estimate space
+	 * for the various things we need to store.
+	 */
+
+	/* Estimate space for fixed-size state. */
+	shm_toc_estimate_chunk(&pcxt->estimator,
+						   sizeof(FixedParallelExecutorState));
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/* Estimate space for query text. */
+	query_len = strlen(estate->es_sourceText);
+	shm_toc_estimate_chunk(&pcxt->estimator, query_len + 1);
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/* Estimate space for serialized PlannedStmt. */
+	pstmt_len = strlen(pstmt_data) + 1;
+	shm_toc_estimate_chunk(&pcxt->estimator, pstmt_len);
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/* Estimate space for serialized ParamListInfo. */
+	paramlistinfo_len = EstimateParamListSpace(estate->es_param_list_info);
+	shm_toc_estimate_chunk(&pcxt->estimator, paramlistinfo_len);
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/*
+	 * Estimate space for BufferUsage.
+	 *
+	 * If EXPLAIN is not in use and there are no extensions loaded that care,
+	 * we could skip this.  But we have no way of knowing whether anyone's
+	 * looking at pgBufferUsage, so do it unconditionally.
+	 */
+	shm_toc_estimate_chunk(&pcxt->estimator,
+						   mul_size(sizeof(BufferUsage), pcxt->nworkers));
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/*
+	 * Same thing for WalUsage.
+	 */
+	shm_toc_estimate_chunk(&pcxt->estimator,
+						   mul_size(sizeof(WalUsage), pcxt->nworkers));
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/* Estimate space for tuple queues. */
+	shm_toc_estimate_chunk(&pcxt->estimator,
+						   mul_size(PARALLEL_TUPLE_QUEUE_SIZE, pcxt->nworkers));
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/*
+	 * Give parallel-aware nodes a chance to add to the estimates, and get a
+	 * count of how many PlanState nodes there are.
+	 */
+	e.pcxt = pcxt;
+	e.nnodes = 0;
+	ExecParallelEstimate(planstate, &e);
+
+	/* Estimate space for instrumentation, if required. */
+	if (estate->es_instrument)
+	{
+		instrumentation_len =
+			offsetof(SharedExecutorInstrumentation, plan_node_id) +
+			sizeof(int) * e.nnodes;
+		instrumentation_len = MAXALIGN(instrumentation_len);
+		instrument_offset = instrumentation_len;
+		instrumentation_len +=
+			mul_size(sizeof(Instrumentation),
+					 mul_size(e.nnodes, nworkers));
+		shm_toc_estimate_chunk(&pcxt->estimator, instrumentation_len);
+		shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+		/* Estimate space for JIT instrumentation, if required. */
+		if (estate->es_jit_flags != PGJIT_NONE)
+		{
+			jit_instrumentation_len =
+				offsetof(SharedJitInstrumentation, jit_instr) +
+				sizeof(JitInstrumentation) * nworkers;
+			shm_toc_estimate_chunk(&pcxt->estimator, jit_instrumentation_len);
+			shm_toc_estimate_keys(&pcxt->estimator, 1);
+		}
+	}
+
+	/* Estimate space for DSA area. */
+	shm_toc_estimate_chunk(&pcxt->estimator, dsa_minsize);
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+
+	/* Everyone's had a chance to ask for space, so now create the DSM. */
+	InitializeParallelDSM(pcxt);
+
+	/*
+	 * OK, now we have a dynamic shared memory segment, and it should be big
+	 * enough to store all of the data we estimated we would want to put into
+	 * it, plus whatever general stuff (not specifically executor-related) the
+	 * ParallelContext itself needs to store there.  None of the space we
+	 * asked for has been allocated or initialized yet, though, so do that.
+	 */
+
+	/* Store fixed-size state. */
+	fpes = shm_toc_allocate(pcxt->toc, sizeof(FixedParallelExecutorState));
+	fpes->tuples_needed = tuples_needed;
+	fpes->param_exec = InvalidDsaPointer;
+	fpes->eflags = estate->es_top_eflags;
+	fpes->jit_flags = estate->es_jit_flags;
+	shm_toc_insert(pcxt->toc, PARALLEL_KEY_EXECUTOR_FIXED, fpes);
+
+	/* Store query string */
+	query_string = shm_toc_allocate(pcxt->toc, query_len + 1);
+	memcpy(query_string, estate->es_sourceText, query_len + 1);
+	shm_toc_insert(pcxt->toc, PARALLEL_KEY_QUERY_TEXT, query_string);
+
+	/* Store serialized PlannedStmt. */
+	pstmt_space = shm_toc_allocate(pcxt->toc, pstmt_len);
+	memcpy(pstmt_space, pstmt_data, pstmt_len);
+	shm_toc_insert(pcxt->toc, PARALLEL_KEY_PLANNEDSTMT, pstmt_space);
+
+	/* Store serialized ParamListInfo. */
+	paramlistinfo_space = shm_toc_allocate(pcxt->toc, paramlistinfo_len);
+	shm_toc_insert(pcxt->toc, PARALLEL_KEY_PARAMLISTINFO, paramlistinfo_space);
+	SerializeParamList(estate->es_param_list_info, &paramlistinfo_space);
+
+	/* Allocate space for each worker's BufferUsage; no need to initialize. */
+	bufusage_space = shm_toc_allocate(pcxt->toc,
+									  mul_size(sizeof(BufferUsage), pcxt->nworkers));
+	shm_toc_insert(pcxt->toc, PARALLEL_KEY_BUFFER_USAGE, bufusage_space);
+	pei->buffer_usage = bufusage_space;
+
+	/* Same for WalUsage. */
+	walusage_space = shm_toc_allocate(pcxt->toc,
+									  mul_size(sizeof(WalUsage), pcxt->nworkers));
+	shm_toc_insert(pcxt->toc, PARALLEL_KEY_WAL_USAGE, walusage_space);
+	pei->wal_usage = walusage_space;
+
+	/* Set up the tuple queues that the workers will write into. */
+	pei->tqueue = ExecParallelSetupTupleQueues(pcxt, false);
+
+	/* We don't need the TupleQueueReaders yet, though. */
+	pei->reader = NULL;
+
+	/*
+	 * If instrumentation options were supplied, allocate space for the data.
+	 * It only gets partially initialized here; the rest happens during
+	 * ExecParallelInitializeDSM.
+	 */
+	if (estate->es_instrument)
+	{
+		Instrumentation *instrument;
+		int			i;
+
+		instrumentation = shm_toc_allocate(pcxt->toc, instrumentation_len);
+		instrumentation->instrument_options = estate->es_instrument;
+		instrumentation->instrument_offset = instrument_offset;
+		instrumentation->num_workers = nworkers;
+		instrumentation->num_plan_nodes = e.nnodes;
+		instrument = GetInstrumentationArray(instrumentation);
+		for (i = 0; i < nworkers * e.nnodes; ++i)
+			InstrInit(&instrument[i], estate->es_instrument);
+		shm_toc_insert(pcxt->toc, PARALLEL_KEY_INSTRUMENTATION,
+					   instrumentation);
+		pei->instrumentation = instrumentation;
+
+		if (estate->es_jit_flags != PGJIT_NONE)
+		{
+			jit_instrumentation = shm_toc_allocate(pcxt->toc,
+												   jit_instrumentation_len);
+			jit_instrumentation->num_workers = nworkers;
+			memset(jit_instrumentation->jit_instr, 0,
+				   sizeof(JitInstrumentation) * nworkers);
+			shm_toc_insert(pcxt->toc, PARALLEL_KEY_JIT_INSTRUMENTATION,
+						   jit_instrumentation);
+			pei->jit_instrumentation = jit_instrumentation;
+		}
+	}
+
+	/*
+	 * Create a DSA area that can be used by the leader and all workers.
+	 * (However, if we failed to create a DSM and are using private memory
+	 * instead, then skip this.)
+	 */
+	if (pcxt->seg != NULL)
+	{
+		char	   *area_space;
+
+		area_space = shm_toc_allocate(pcxt->toc, dsa_minsize);
+		shm_toc_insert(pcxt->toc, PARALLEL_KEY_DSA, area_space);
+		pei->area = dsa_create_in_place(area_space, dsa_minsize,
+										LWTRANCHE_PARALLEL_QUERY_DSA,
+										pcxt->seg);
+
+		/*
+		 * Serialize parameters, if any, using DSA storage.  We don't dare use
+		 * the main parallel query DSM for this because we might relaunch
+		 * workers after the values have changed (and thus the amount of
+		 * storage required has changed).
+		 */
+		if (!bms_is_empty(sendParams))
+		{
+			pei->param_exec = SerializeParamExecParams(estate, sendParams,
+													   pei->area);
+			fpes->param_exec = pei->param_exec;
+		}
+	}
+
+	/*
+	 * Give parallel-aware nodes a chance to initialize their shared data.
+	 * This also initializes the elements of instrumentation->ps_instrument,
+	 * if it exists.
+	 */
+	d.pcxt = pcxt;
+	d.instrumentation = instrumentation;
+	d.nnodes = 0;
+
+	/* Install our DSA area while initializing the plan. */
+	estate->es_query_dsa = pei->area;
+	ExecParallelInitializeDSM(planstate, &d);
+	estate->es_query_dsa = NULL;
+
+	/*
+	 * Make sure that the world hasn't shifted under our feet.  This could
+	 * probably just be an Assert(), but let's be conservative for now.
+	 */
+	if (e.nnodes != d.nnodes)
+		elog(ERROR, "inconsistent count of PlanState nodes");
+
+	/* OK, we're ready to rock and roll. */
+	return pei;
+}
+
+/*
+ * Set up tuple queue readers to read the results of a parallel subplan.
+ *
+ * This is separate from ExecInitParallelPlan() because we can launch the
+ * worker processes and let them start doing something before we do this.
+ */
+void
+ExecParallelCreateReaders(ParallelExecutorInfo *pei)
+{
+	int			nworkers = pei->pcxt->nworkers_launched;
+	int			i;
+
+	Assert(pei->reader == NULL);
+
+	if (nworkers > 0)
+	{
+		pei->reader = (TupleQueueReader **)
+			palloc(nworkers * sizeof(TupleQueueReader *));
+
+		for (i = 0; i < nworkers; i++)
+		{
+			shm_mq_set_handle(pei->tqueue[i],
+							  pei->pcxt->worker[i].bgwhandle);
+			pei->reader[i] = CreateTupleQueueReader(pei->tqueue[i]);
+		}
+	}
+}
+
+/*
+ * Re-initialize the parallel executor shared memory state before launching
+ * a fresh batch of workers.
+ */
+void
+ExecParallelReinitialize(PlanState *planstate,
+						 ParallelExecutorInfo *pei,
+						 Bitmapset *sendParams)
+{
+	EState	   *estate = planstate->state;
+	FixedParallelExecutorState *fpes;
+
+	/* Old workers must already be shut down */
+	Assert(pei->finished);
+
+	/*
+	 * Force any initplan outputs that we're going to pass to workers to be
+	 * evaluated, if they weren't already (see comments in
+	 * ExecInitParallelPlan).
+	 */
+	ExecSetParamPlanMulti(sendParams, GetPerTupleExprContext(estate));
+
+	ReinitializeParallelDSM(pei->pcxt);
+	pei->tqueue = ExecParallelSetupTupleQueues(pei->pcxt, true);
+	pei->reader = NULL;
+	pei->finished = false;
+
+	fpes = shm_toc_lookup(pei->pcxt->toc, PARALLEL_KEY_EXECUTOR_FIXED, false);
+
+	/* Free any serialized parameters from the last round. */
+	if (DsaPointerIsValid(fpes->param_exec))
+	{
+		dsa_free(pei->area, fpes->param_exec);
+		fpes->param_exec = InvalidDsaPointer;
+	}
+
+	/* Serialize current parameter values if required. */
+	if (!bms_is_empty(sendParams))
+	{
+		pei->param_exec = SerializeParamExecParams(estate, sendParams,
+												   pei->area);
+		fpes->param_exec = pei->param_exec;
+	}
+
+	/* Traverse plan tree and let each child node reset associated state. */
+	estate->es_query_dsa = pei->area;
+	ExecParallelReInitializeDSM(planstate, pei->pcxt);
+	estate->es_query_dsa = NULL;
+}
+
+/*
+ * Traverse plan tree to reinitialize per-node dynamic shared memory state
+ */
+static bool
+ExecParallelReInitializeDSM(PlanState *planstate,
+							ParallelContext *pcxt)
+{
+	if (planstate == NULL)
+		return false;
+
+	/*
+	 * Call reinitializers for DSM-using plan nodes.
+	 */
+	switch (nodeTag(planstate))
+	{
+		case T_SeqScanState:
+			if (planstate->plan->parallel_aware)
+				ExecSeqScanReInitializeDSM((SeqScanState *) planstate,
+										   pcxt);
+			break;
+		case T_IndexScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexScanReInitializeDSM((IndexScanState *) planstate,
+											 pcxt);
+			break;
+		case T_IndexOnlyScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexOnlyScanReInitializeDSM((IndexOnlyScanState *) planstate,
+												 pcxt);
+			break;
+		case T_ForeignScanState:
+			if (planstate->plan->parallel_aware)
+				ExecForeignScanReInitializeDSM((ForeignScanState *) planstate,
+											   pcxt);
+			break;
+		case T_AppendState:
+			if (planstate->plan->parallel_aware)
+				ExecAppendReInitializeDSM((AppendState *) planstate, pcxt);
+			break;
+		case T_CustomScanState:
+			if (planstate->plan->parallel_aware)
+				ExecCustomScanReInitializeDSM((CustomScanState *) planstate,
+											  pcxt);
+			break;
+		case T_BitmapHeapScanState:
+			if (planstate->plan->parallel_aware)
+				ExecBitmapHeapReInitializeDSM((BitmapHeapScanState *) planstate,
+											  pcxt);
+			break;
+		case T_HashJoinState:
+			if (planstate->plan->parallel_aware)
+				ExecHashJoinReInitializeDSM((HashJoinState *) planstate,
+											pcxt);
+			break;
+		case T_HashState:
+		case T_SortState:
+		case T_IncrementalSortState:
+		case T_MemoizeState:
+			/* these nodes have DSM state, but no reinitialization is required */
+			break;
+
+		default:
+			break;
+	}
+
+	return planstate_tree_walker(planstate, ExecParallelReInitializeDSM, pcxt);
+}
+
+/*
+ * Copy instrumentation information about this node and its descendants from
+ * dynamic shared memory.
+ */
+static bool
+ExecParallelRetrieveInstrumentation(PlanState *planstate,
+									SharedExecutorInstrumentation *instrumentation)
+{
+	Instrumentation *instrument;
+	int			i;
+	int			n;
+	int			ibytes;
+	int			plan_node_id = planstate->plan->plan_node_id;
+	MemoryContext oldcontext;
+
+	/* Find the instrumentation for this node. */
+	for (i = 0; i < instrumentation->num_plan_nodes; ++i)
+		if (instrumentation->plan_node_id[i] == plan_node_id)
+			break;
+	if (i >= instrumentation->num_plan_nodes)
+		elog(ERROR, "plan node %d not found", plan_node_id);
+
+	/* Accumulate the statistics from all workers. */
+	instrument = GetInstrumentationArray(instrumentation);
+	instrument += i * instrumentation->num_workers;
+	for (n = 0; n < instrumentation->num_workers; ++n)
+		InstrAggNode(planstate->instrument, &instrument[n]);
+
+	/*
+	 * Also store the per-worker detail.
+	 *
+	 * Worker instrumentation should be allocated in the same context as the
+	 * regular instrumentation information, which is the per-query context.
+	 * Switch into per-query memory context.
+	 */
+	oldcontext = MemoryContextSwitchTo(planstate->state->es_query_cxt);
+	ibytes = mul_size(instrumentation->num_workers, sizeof(Instrumentation));
+	planstate->worker_instrument =
+		palloc(ibytes + offsetof(WorkerInstrumentation, instrument));
+	MemoryContextSwitchTo(oldcontext);
+
+	planstate->worker_instrument->num_workers = instrumentation->num_workers;
+	memcpy(&planstate->worker_instrument->instrument, instrument, ibytes);
+
+	/* Perform any node-type-specific work that needs to be done. */
+	switch (nodeTag(planstate))
+	{
+		case T_SortState:
+			ExecSortRetrieveInstrumentation((SortState *) planstate);
+			break;
+		case T_IncrementalSortState:
+			ExecIncrementalSortRetrieveInstrumentation((IncrementalSortState *) planstate);
+			break;
+		case T_HashState:
+			ExecHashRetrieveInstrumentation((HashState *) planstate);
+			break;
+		case T_AggState:
+			ExecAggRetrieveInstrumentation((AggState *) planstate);
+			break;
+		case T_MemoizeState:
+			ExecMemoizeRetrieveInstrumentation((MemoizeState *) planstate);
+			break;
+		default:
+			break;
+	}
+
+	return planstate_tree_walker(planstate, ExecParallelRetrieveInstrumentation,
+								 instrumentation);
+}
+
+/*
+ * Add up the workers' JIT instrumentation from dynamic shared memory.
+ */
+static void
+ExecParallelRetrieveJitInstrumentation(PlanState *planstate,
+									   SharedJitInstrumentation *shared_jit)
+{
+	JitInstrumentation *combined;
+	int			ibytes;
+
+	int			n;
+
+	/*
+	 * Accumulate worker JIT instrumentation into the combined JIT
+	 * instrumentation, allocating it if required.
+	 */
+	if (!planstate->state->es_jit_worker_instr)
+		planstate->state->es_jit_worker_instr =
+			MemoryContextAllocZero(planstate->state->es_query_cxt, sizeof(JitInstrumentation));
+	combined = planstate->state->es_jit_worker_instr;
+
+	/* Accumulate all the workers' instrumentations. */
+	for (n = 0; n < shared_jit->num_workers; ++n)
+		InstrJitAgg(combined, &shared_jit->jit_instr[n]);
+
+	/*
+	 * Store the per-worker detail.
+	 *
+	 * Similar to ExecParallelRetrieveInstrumentation(), allocate the
+	 * instrumentation in per-query context.
+	 */
+	ibytes = offsetof(SharedJitInstrumentation, jit_instr)
+		+ mul_size(shared_jit->num_workers, sizeof(JitInstrumentation));
+	planstate->worker_jit_instrument =
+		MemoryContextAlloc(planstate->state->es_query_cxt, ibytes);
+
+	memcpy(planstate->worker_jit_instrument, shared_jit, ibytes);
+}
+
+/*
+ * Finish parallel execution.  We wait for parallel workers to finish, and
+ * accumulate their buffer/WAL usage.
+ */
+void
+ExecParallelFinish(ParallelExecutorInfo *pei)
+{
+	int			nworkers = pei->pcxt->nworkers_launched;
+	int			i;
+
+	/* Make this be a no-op if called twice in a row. */
+	if (pei->finished)
+		return;
+
+	/*
+	 * Detach from tuple queues ASAP, so that any still-active workers will
+	 * notice that no further results are wanted.
+	 */
+	if (pei->tqueue != NULL)
+	{
+		for (i = 0; i < nworkers; i++)
+			shm_mq_detach(pei->tqueue[i]);
+		pfree(pei->tqueue);
+		pei->tqueue = NULL;
+	}
+
+	/*
+	 * While we're waiting for the workers to finish, let's get rid of the
+	 * tuple queue readers.  (Any other local cleanup could be done here too.)
+	 */
+	if (pei->reader != NULL)
+	{
+		for (i = 0; i < nworkers; i++)
+			DestroyTupleQueueReader(pei->reader[i]);
+		pfree(pei->reader);
+		pei->reader = NULL;
+	}
+
+	/* Now wait for the workers to finish. */
+	WaitForParallelWorkersToFinish(pei->pcxt);
+
+	/*
+	 * Next, accumulate buffer/WAL usage.  (This must wait for the workers to
+	 * finish, or we might get incomplete data.)
+	 */
+	for (i = 0; i < nworkers; i++)
+		InstrAccumParallelQuery(&pei->buffer_usage[i], &pei->wal_usage[i]);
+
+	pei->finished = true;
+}
+
+/*
+ * Accumulate instrumentation, and then clean up whatever ParallelExecutorInfo
+ * resources still exist after ExecParallelFinish.  We separate these
+ * routines because someone might want to examine the contents of the DSM
+ * after ExecParallelFinish and before calling this routine.
+ */
+void
+ExecParallelCleanup(ParallelExecutorInfo *pei)
+{
+	/* Accumulate instrumentation, if any. */
+	if (pei->instrumentation)
+		ExecParallelRetrieveInstrumentation(pei->planstate,
+											pei->instrumentation);
+
+	/* Accumulate JIT instrumentation, if any. */
+	if (pei->jit_instrumentation)
+		ExecParallelRetrieveJitInstrumentation(pei->planstate,
+											   pei->jit_instrumentation);
+
+	/* Free any serialized parameters. */
+	if (DsaPointerIsValid(pei->param_exec))
+	{
+		dsa_free(pei->area, pei->param_exec);
+		pei->param_exec = InvalidDsaPointer;
+	}
+	if (pei->area != NULL)
+	{
+		dsa_detach(pei->area);
+		pei->area = NULL;
+	}
+	if (pei->pcxt != NULL)
+	{
+		DestroyParallelContext(pei->pcxt);
+		pei->pcxt = NULL;
+	}
+	pfree(pei);
+}
+
+/*
+ * Create a DestReceiver to write tuples we produce to the shm_mq designated
+ * for that purpose.
+ */
+static DestReceiver *
+ExecParallelGetReceiver(dsm_segment *seg, shm_toc *toc)
+{
+	char	   *mqspace;
+	shm_mq	   *mq;
+
+	mqspace = shm_toc_lookup(toc, PARALLEL_KEY_TUPLE_QUEUE, false);
+	mqspace += ParallelWorkerNumber * PARALLEL_TUPLE_QUEUE_SIZE;
+	mq = (shm_mq *) mqspace;
+	shm_mq_set_sender(mq, MyProc);
+	return CreateTupleQueueDestReceiver(shm_mq_attach(mq, seg, NULL));
+}
+
+/*
+ * Create a QueryDesc for the PlannedStmt we are to execute, and return it.
+ */
+static QueryDesc *
+ExecParallelGetQueryDesc(shm_toc *toc, DestReceiver *receiver,
+						 int instrument_options)
+{
+	char	   *pstmtspace;
+	char	   *paramspace;
+	PlannedStmt *pstmt;
+	ParamListInfo paramLI;
+	char	   *queryString;
+
+	/* Get the query string from shared memory */
+	queryString = shm_toc_lookup(toc, PARALLEL_KEY_QUERY_TEXT, false);
+
+	/* Reconstruct leader-supplied PlannedStmt. */
+	pstmtspace = shm_toc_lookup(toc, PARALLEL_KEY_PLANNEDSTMT, false);
+	pstmt = (PlannedStmt *) stringToNode(pstmtspace);
+
+	/* Reconstruct ParamListInfo. */
+	paramspace = shm_toc_lookup(toc, PARALLEL_KEY_PARAMLISTINFO, false);
+	paramLI = RestoreParamList(&paramspace);
+
+	/* Create a QueryDesc for the query. */
+	return CreateQueryDesc(pstmt,
+						   queryString,
+						   GetActiveSnapshot(), InvalidSnapshot,
+						   receiver, paramLI, NULL, instrument_options);
+}
+
+/*
+ * Copy instrumentation information from this node and its descendants into
+ * dynamic shared memory, so that the parallel leader can retrieve it.
+ */
+static bool
+ExecParallelReportInstrumentation(PlanState *planstate,
+								  SharedExecutorInstrumentation *instrumentation)
+{
+	int			i;
+	int			plan_node_id = planstate->plan->plan_node_id;
+	Instrumentation *instrument;
+
+	InstrEndLoop(planstate->instrument);
+
+	/*
+	 * If we shuffled the plan_node_id values in ps_instrument into sorted
+	 * order, we could use binary search here.  This might matter someday if
+	 * we're pushing down sufficiently large plan trees.  For now, do it the
+	 * slow, dumb way.
+	 */
+	for (i = 0; i < instrumentation->num_plan_nodes; ++i)
+		if (instrumentation->plan_node_id[i] == plan_node_id)
+			break;
+	if (i >= instrumentation->num_plan_nodes)
+		elog(ERROR, "plan node %d not found", plan_node_id);
+
+	/*
+	 * Add our statistics to the per-node, per-worker totals.  It's possible
+	 * that this could happen more than once if we relaunched workers.
+	 */
+	instrument = GetInstrumentationArray(instrumentation);
+	instrument += i * instrumentation->num_workers;
+	Assert(IsParallelWorker());
+	Assert(ParallelWorkerNumber < instrumentation->num_workers);
+	InstrAggNode(&instrument[ParallelWorkerNumber], planstate->instrument);
+
+	return planstate_tree_walker(planstate, ExecParallelReportInstrumentation,
+								 instrumentation);
+}
+
+/*
+ * Initialize the PlanState and its descendants with the information
+ * retrieved from shared memory.  This has to be done once the PlanState
+ * is allocated and initialized by executor; that is, after ExecutorStart().
+ */
+static bool
+ExecParallelInitializeWorker(PlanState *planstate, ParallelWorkerContext *pwcxt)
+{
+	if (planstate == NULL)
+		return false;
+
+	switch (nodeTag(planstate))
+	{
+		case T_SeqScanState:
+			if (planstate->plan->parallel_aware)
+				ExecSeqScanInitializeWorker((SeqScanState *) planstate, pwcxt);
+			break;
+		case T_IndexScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexScanInitializeWorker((IndexScanState *) planstate,
+											  pwcxt);
+			break;
+		case T_IndexOnlyScanState:
+			if (planstate->plan->parallel_aware)
+				ExecIndexOnlyScanInitializeWorker((IndexOnlyScanState *) planstate,
+												  pwcxt);
+			break;
+		case T_ForeignScanState:
+			if (planstate->plan->parallel_aware)
+				ExecForeignScanInitializeWorker((ForeignScanState *) planstate,
+												pwcxt);
+			break;
+		case T_AppendState:
+			if (planstate->plan->parallel_aware)
+				ExecAppendInitializeWorker((AppendState *) planstate, pwcxt);
+			break;
+		case T_CustomScanState:
+			if (planstate->plan->parallel_aware)
+				ExecCustomScanInitializeWorker((CustomScanState *) planstate,
+											   pwcxt);
+			break;
+		case T_BitmapHeapScanState:
+			if (planstate->plan->parallel_aware)
+				ExecBitmapHeapInitializeWorker((BitmapHeapScanState *) planstate,
+											   pwcxt);
+			break;
+		case T_HashJoinState:
+			if (planstate->plan->parallel_aware)
+				ExecHashJoinInitializeWorker((HashJoinState *) planstate,
+											 pwcxt);
+			break;
+		case T_HashState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecHashInitializeWorker((HashState *) planstate, pwcxt);
+			break;
+		case T_SortState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecSortInitializeWorker((SortState *) planstate, pwcxt);
+			break;
+		case T_IncrementalSortState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecIncrementalSortInitializeWorker((IncrementalSortState *) planstate,
+												pwcxt);
+			break;
+		case T_AggState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecAggInitializeWorker((AggState *) planstate, pwcxt);
+			break;
+		case T_MemoizeState:
+			/* even when not parallel-aware, for EXPLAIN ANALYZE */
+			ExecMemoizeInitializeWorker((MemoizeState *) planstate, pwcxt);
+			break;
+		default:
+			break;
+	}
+
+	return planstate_tree_walker(planstate, ExecParallelInitializeWorker,
+								 pwcxt);
+}
+
+/*
+ * Main entrypoint for parallel query worker processes.
+ *
+ * We reach this function from ParallelWorkerMain, so the setup necessary to
+ * create a sensible parallel environment has already been done;
+ * ParallelWorkerMain worries about stuff like the transaction state, combo
+ * CID mappings, and GUC values, so we don't need to deal with any of that
+ * here.
+ *
+ * Our job is to deal with concerns specific to the executor.  The parallel
+ * group leader will have stored a serialized PlannedStmt, and it's our job
+ * to execute that plan and write the resulting tuples to the appropriate
+ * tuple queue.  Various bits of supporting information that we need in order
+ * to do this are also stored in the dsm_segment and can be accessed through
+ * the shm_toc.
+ */
+void
+ParallelQueryMain(dsm_segment *seg, shm_toc *toc)
+{
+	FixedParallelExecutorState *fpes;
+	BufferUsage *buffer_usage;
+	WalUsage   *wal_usage;
+	DestReceiver *receiver;
+	QueryDesc  *queryDesc;
+	SharedExecutorInstrumentation *instrumentation;
+	SharedJitInstrumentation *jit_instrumentation;
+	int			instrument_options = 0;
+	void	   *area_space;
+	dsa_area   *area;
+	ParallelWorkerContext pwcxt;
+
+	/* Get fixed-size state. */
+	fpes = shm_toc_lookup(toc, PARALLEL_KEY_EXECUTOR_FIXED, false);
+
+	/* Set up DestReceiver, SharedExecutorInstrumentation, and QueryDesc. */
+	receiver = ExecParallelGetReceiver(seg, toc);
+	instrumentation = shm_toc_lookup(toc, PARALLEL_KEY_INSTRUMENTATION, true);
+	if (instrumentation != NULL)
+		instrument_options = instrumentation->instrument_options;
+	jit_instrumentation = shm_toc_lookup(toc, PARALLEL_KEY_JIT_INSTRUMENTATION,
+										 true);
+	queryDesc = ExecParallelGetQueryDesc(toc, receiver, instrument_options);
+
+	/* Setting debug_query_string for individual workers */
+	debug_query_string = queryDesc->sourceText;
+
+	/* Report workers' query and queryId for monitoring purposes */
+	pgstat_report_activity(STATE_RUNNING, debug_query_string);
+
+	/* Attach to the dynamic shared memory area. */
+	area_space = shm_toc_lookup(toc, PARALLEL_KEY_DSA, false);
+	area = dsa_attach_in_place(area_space, seg);
+
+	/* Start up the executor */
+	queryDesc->plannedstmt->jitFlags = fpes->jit_flags;
+	ExecutorStart(queryDesc, fpes->eflags);
+
+	/* Special executor initialization steps for parallel workers */
+	queryDesc->planstate->state->es_query_dsa = area;
+	if (DsaPointerIsValid(fpes->param_exec))
+	{
+		char	   *paramexec_space;
+
+		paramexec_space = dsa_get_address(area, fpes->param_exec);
+		RestoreParamExecParams(paramexec_space, queryDesc->estate);
+
+	}
+	pwcxt.toc = toc;
+	pwcxt.seg = seg;
+	ExecParallelInitializeWorker(queryDesc->planstate, &pwcxt);
+
+	/* Pass down any tuple bound */
+	ExecSetTupleBound(fpes->tuples_needed, queryDesc->planstate);
+
+	/*
+	 * Prepare to track buffer/WAL usage during query execution.
+	 *
+	 * We do this after starting up the executor to match what happens in the
+	 * leader, which also doesn't count buffer accesses and WAL activity that
+	 * occur during executor startup.
+	 */
+	InstrStartParallelQuery();
+
+	/*
+	 * Run the plan.  If we specified a tuple bound, be careful not to demand
+	 * more tuples than that.
+	 */
+	ExecutorRun(queryDesc,
+				ForwardScanDirection,
+				fpes->tuples_needed < 0 ? (int64) 0 : fpes->tuples_needed,
+				true);
+
+	/* Shut down the executor */
+	ExecutorFinish(queryDesc);
+
+	/* Report buffer/WAL usage during parallel execution. */
+	buffer_usage = shm_toc_lookup(toc, PARALLEL_KEY_BUFFER_USAGE, false);
+	wal_usage = shm_toc_lookup(toc, PARALLEL_KEY_WAL_USAGE, false);
+	InstrEndParallelQuery(&buffer_usage[ParallelWorkerNumber],
+						  &wal_usage[ParallelWorkerNumber]);
+
+	/* Report instrumentation data if any instrumentation options are set. */
+	if (instrumentation != NULL)
+		ExecParallelReportInstrumentation(queryDesc->planstate,
+										  instrumentation);
+
+	/* Report JIT instrumentation data if any */
+	if (queryDesc->estate->es_jit && jit_instrumentation != NULL)
+	{
+		Assert(ParallelWorkerNumber < jit_instrumentation->num_workers);
+		jit_instrumentation->jit_instr[ParallelWorkerNumber] =
+			queryDesc->estate->es_jit->instr;
+	}
+
+	/* Must do this after capturing instrumentation. */
+	ExecutorEnd(queryDesc);
+
+	/* Cleanup. */
+	dsa_detach(area);
+	FreeQueryDesc(queryDesc);
+	receiver->rDestroy(receiver);
+}