/* ----------------------------------------------------------------
 *		ExecInitWorkTableScan
 * ----------------------------------------------------------------
 */
WorkTableScanState *
ExecInitWorkTableScan(WorkTableScan *node, EState *estate, int eflags)
{
	WorkTableScanState *scanstate;

	/* check for unsupported flags */
	/*
	 * GPDB_84_MERGE_FIXME: Make sure we don't require EXEC_FLAG_BACKWARD
	 * in GPDB.
	 */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * WorkTableScan should not have any children.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create new WorkTableScanState for node
	 */
	scanstate = makeNode(WorkTableScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->rustate = NULL;	/* we'll set this later */

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) scanstate);
	scanstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) scanstate);

#define WORKTABLESCAN_NSLOTS 2

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
	ExecInitScanTupleSlot(estate, &scanstate->ss);

	/*
	 * Initialize result tuple type, but not yet projection info.
	 */
	ExecAssignResultTypeFromTL(&scanstate->ss.ps);

	/* scanstate->ss.ps.ps_TupFromTlist = false; */

	return scanstate;
}

/* ----------------------------------------------------------------
 *		ExecInitSeqScan
 * ----------------------------------------------------------------
 */
SeqScanState *
ExecInitSeqScan(SeqScan *node, EState *estate, int eflags)
{
	SeqScanState *scanstate;
	AttrNumber ctid_attrno;

	/*
	 * Once upon a time it was possible to have an outerPlan of a SeqScan, but
	 * not any more.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create state structure
	 */
	scanstate = makeNode(SeqScanState);
	scanstate->ps.plan = (Plan *) node;
	scanstate->ps.state = estate;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ps);

	/*
	 * initialize child expressions
	 */
	scanstate->ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->plan.targetlist,
					 (PlanState *) scanstate);
	scanstate->ps.qual = (List *)
		ExecInitExpr((Expr *) node->plan.qual,
					 (PlanState *) scanstate);

#define SEQSCAN_NSLOTS 2

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->ps);
	ExecInitScanTupleSlot(estate, scanstate);

	/*
	 * initialize scan relation
	 */
	InitScanRelation(scanstate, estate);

	scanstate->ps.ps_TupFromTlist = false;

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&scanstate->ps);
	ExecAssignScanProjectionInfo(scanstate);

	return scanstate;
}

/* ----------------------------------------------------------------
 *		ExecInitAppendOnlyScan
 * ----------------------------------------------------------------
 */
AppendOnlyScanState *
ExecInitAppendOnlyScan(AppendOnlyScan *node, EState *estate, int eflags)
{
	AppendOnlyScanState	*appendonlystate;
	Relation			currentRelation;
	
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create state structure
	 */
	appendonlystate = makeNode(AppendOnlyScanState);
	appendonlystate->ss.ps.plan = (Plan *) node;
	appendonlystate->ss.ps.state = estate;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &appendonlystate->ss.ps);

	/*
	 * initialize child expressions
	 */
	appendonlystate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) appendonlystate);
	appendonlystate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) appendonlystate);

#define AOSCAN_NSLOTS 2

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &appendonlystate->ss.ps);
	ExecInitScanTupleSlot(estate, &appendonlystate->ss);

	/*
	 * get the relation object id from the relid'th entry in the range table
	 * and open that relation.
	 */
	currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);	
	appendonlystate->ss.ss_currentRelation = currentRelation;
	ExecAssignScanType(&appendonlystate->ss, RelationGetDescr(currentRelation));
	
	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&appendonlystate->ss.ps);
	ExecAssignScanProjectionInfo(&appendonlystate->ss);

	initGpmonPktForAppendOnlyScan((Plan *)node, &appendonlystate->ss.ps.gpmon_pkt, estate);

	return appendonlystate;
}

/* -----------------
 * ExecInitGroup
 *
 *	Creates the run-time information for the group node produced by the
 *	planner and initializes its outer subtree
 * -----------------
 */
GroupState *
ExecInitGroup(Group *node, EState *estate, int eflags)
{
	GroupState *grpstate;

	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * create state structure
	 */
	grpstate = makeNode(GroupState);
	grpstate->ss.ps.plan = (Plan *) node;
	grpstate->ss.ps.state = estate;
	grpstate->ss.ps.ExecProcNode = ExecGroup;
	grpstate->grp_done = false;

	/*
	 * create expression context
	 */
	ExecAssignExprContext(estate, &grpstate->ss.ps);

	/*
	 * tuple table initialization
	 */
	ExecInitScanTupleSlot(estate, &grpstate->ss);
	ExecInitResultTupleSlot(estate, &grpstate->ss.ps);

	/*
	 * initialize child expressions
	 */
	grpstate->ss.ps.qual =
		ExecInitQual(node->plan.qual, (PlanState *) grpstate);

	/*
	 * initialize child nodes
	 */
	outerPlanState(grpstate) = ExecInitNode(outerPlan(node), estate, eflags);

	/*
	 * initialize tuple type.
	 */
	ExecAssignScanTypeFromOuterPlan(&grpstate->ss);

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&grpstate->ss.ps);
	ExecAssignProjectionInfo(&grpstate->ss.ps, NULL);

	/*
	 * Precompute fmgr lookup data for inner loop
	 */
	grpstate->eqfunctions =
		execTuplesMatchPrepare(node->numCols,
							   node->grpOperators);

	return grpstate;
}

/* ----------------------------------------------------------------
 *		ExecInitWorkTableScan
 * ----------------------------------------------------------------
 */
WorkTableScanState *
ExecInitWorkTableScan(WorkTableScan *node, EState *estate, int eflags)
{
	WorkTableScanState *scanstate;

	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * WorkTableScan should not have any children.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create new WorkTableScanState for node
	 */
	scanstate = makeNode(WorkTableScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->ss.ps.ExecProcNode = ExecWorkTableScan;
	scanstate->rustate = NULL;	/* we'll set this later */

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	/*
	 * tuple table initialization
	 */
	ExecInitResultTypeTL(&scanstate->ss.ps);

	/* signal that return type is not yet known */
	scanstate->ss.ps.resultopsset = true;
	scanstate->ss.ps.resultopsfixed = false;

	ExecInitScanTupleSlot(estate, &scanstate->ss, NULL, &TTSOpsMinimalTuple);

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.qual =
		ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);

	/*
	 * Do not yet initialize projection info, see ExecWorkTableScan() for
	 * details.
	 */

	return scanstate;
}

/* ----------------------------------------------------------------
 *		ExecInitSeqScan
 * ----------------------------------------------------------------
 */
SeqScanState *
ExecInitSeqScan(SeqScan *node, EState *estate, int eflags)
{
	SeqScanState *scanstate;

	/*
	 * Once upon a time it was possible to have an outerPlan of a SeqScan, but
	 * not any more.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create state structure
	 */
	scanstate = makeNode(SeqScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->ss.ps.ExecProcNode = ExecSeqScan;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.qual =
		ExecInitQual(node->plan.qual, (PlanState *) scanstate);

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
	ExecInitScanTupleSlot(estate, &scanstate->ss);

	/*
	 * initialize scan relation
	 */
	InitScanRelation(scanstate, estate, eflags);

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
	ExecAssignScanProjectionInfo(&scanstate->ss);

	return scanstate;
}

/* ----------------
 *		ExecCreateSlotFromOuterPlan
 * ----------------
 */
void
ExecCreateScanSlotFromOuterPlan(EState *estate,
								ScanState *scanstate,
								const TupleTableSlotOps *tts_ops)
{
	PlanState  *outerPlan;
	TupleDesc	tupDesc;

	outerPlan = outerPlanState(scanstate);
	tupDesc = ExecGetResultType(outerPlan);

	ExecInitScanTupleSlot(estate, scanstate, tupDesc, tts_ops);
}

/* ----------------------------------------------------------------
 *		ExecInitMaterial
 * ----------------------------------------------------------------
 */
MaterialState *
ExecInitMaterial(Material *node, EState *estate)
{
	MaterialState *matstate;
	Plan	   *outerPlan;

	/*
	 * create state structure
	 */
	matstate = makeNode(MaterialState);
	matstate->ss.ps.plan = (Plan *) node;
	matstate->ss.ps.state = estate;

	matstate->tuplestorestate = NULL;
	matstate->eof_underlying = false;

	/*
	 * Miscellaneous initialization
	 *
	 * Materialization nodes don't need ExprContexts because they never call
	 * ExecQual or ExecProject.
	 */

#define MATERIAL_NSLOTS 2

	/*
	 * tuple table initialization
	 *
	 * material nodes only return tuples from their materialized relation.
	 */
	ExecInitResultTupleSlot(estate, &matstate->ss.ps);
	ExecInitScanTupleSlot(estate, &matstate->ss);

	/*
	 * initializes child nodes
	 */
	outerPlan = outerPlan(node);
	outerPlanState(matstate) = ExecInitNode(outerPlan, estate);

	/*
	 * initialize tuple type.  no need to initialize projection info because
	 * this node doesn't do projections.
	 */
	ExecAssignResultTypeFromTL(&matstate->ss.ps);
	ExecAssignScanTypeFromOuterPlan(&matstate->ss);
	matstate->ss.ps.ps_ProjInfo = NULL;

	return matstate;
}

/*
 * InitScanStateInternal
 *   Initialize ScanState common variables for various Scan node.
 */
void
InitScanStateInternal(ScanState *scanState, Plan *plan, EState *estate,
		int eflags, bool initCurrentRelation)
{
	Assert(IsA(plan, SeqScan) ||
		   IsA(plan, AppendOnlyScan) ||
		   IsA(plan, ParquetScan) ||
		   IsA(plan, TableScan) ||
		   IsA(plan, DynamicTableScan) ||
		   IsA(plan, BitmapTableScan));

	PlanState *planState = &scanState->ps;

	planState->plan = plan;
	planState->state = estate;

	/* Create expression evaluation context */
	ExecAssignExprContext(estate, planState);
	
	/* Initialize tuple table slot */
	ExecInitResultTupleSlot(estate, planState);
	ExecInitScanTupleSlot(estate, scanState);
	
	/*
	 * For dynamic table scan, We do not initialize expression states; instead
	 * we wait until the first partition, and initialize the expression state
	 * at that time. Also, for dynamic table scan, we do not need to open the
	 * parent partition relation.
	 */
	if (initCurrentRelation)
	{
		InitScanStateRelationDetails(scanState, plan, estate);
	}

	/* Initialize result tuple type. */
	ExecAssignResultTypeFromTL(planState);

	/*
	 * If eflag contains EXEC_FLAG_REWIND or EXEC_FLAG_BACKWARD or EXEC_FLAG_MARK,
	 * then this node is not eager free safe.
	 */
	scanState->ps.delayEagerFree =
		((eflags & (EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)) != 0);

	/* Currently, only SeqScan supports Mark/Restore. */
	AssertImply((eflags & EXEC_FLAG_MARK) != 0, IsA(plan, SeqScan));

}

extern TuplestoreScanState *
ExecInitTuplestoreScan(TuplestoreScan *node, EState *estate, int eflags)
{
	TuplestoreScanState *tss = makeNode(TuplestoreScanState);
	tss->ss.ps.plan = (Plan *) node;
	tss->ss.ps.state = estate;
	tss->ss.ps.ps_ExprContext = CreateExprContext(estate);

	ExecInitResultTupleSlot(estate, &tss->ss.ps);
	ExecInitScanTupleSlot(estate, &tss->ss);

	ExecSetSlotDescriptor(tss->ss.ss_ScanTupleSlot, node->desc);
	ExecSetSlotDescriptor(tss->ss.ps.ps_ResultTupleSlot, node->desc);

	tss->ss.ps.targetlist = node->scan.plan.targetlist;

	tuplestore_rescan(node->store);

	return tss;
}

/* ----------------------------------------------------------------
 *		ExecInitIndexOnlyScan
 *
 *		Initializes the index scan's state information, creates
 *		scan keys, and opens the base and index relations.
 *
 *		Note: index scans have 2 sets of state information because
 *			  we have to keep track of the base relation and the
 *			  index relation.
 * ----------------------------------------------------------------
 */
IndexOnlyScanState *
ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
{
	IndexOnlyScanState *indexstate;
	Relation	currentRelation;
	bool		relistarget;
	TupleDesc	tupDesc;

	/*
	 * create state structure
	 */
	indexstate = makeNode(IndexOnlyScanState);
	indexstate->ss.ps.plan = (Plan *) node;
	indexstate->ss.ps.state = estate;
	indexstate->ioss_HeapFetches = 0;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &indexstate->ss.ps);

	indexstate->ss.ps.ps_TupFromTlist = false;

	/*
	 * initialize child expressions
	 *
	 * Note: we don't initialize all of the indexorderby expression, only the
	 * sub-parts corresponding to runtime keys (see below).
	 */
	indexstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) indexstate);
	indexstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) indexstate);
	indexstate->indexqual = (List *)
		ExecInitExpr((Expr *) node->indexqual,
					 (PlanState *) indexstate);

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &indexstate->ss.ps);
	ExecInitScanTupleSlot(estate, &indexstate->ss);

	/*
	 * open the base relation and acquire appropriate lock on it.
	 */
	currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);

	indexstate->ss.ss_currentRelation = currentRelation;
	indexstate->ss.ss_currentScanDesc = NULL;	/* no heap scan here */

	/*
	 * Build the scan tuple type using the indextlist generated by the
	 * planner.  We use this, rather than the index's physical tuple
	 * descriptor, because the latter contains storage column types not the
	 * types of the original datums.  (It's the AM's responsibility to return
	 * suitable data anyway.)
	 */
	tupDesc = ExecTypeFromTL(node->indextlist, false);
	ExecAssignScanType(&indexstate->ss, tupDesc);

	/*
	 * Initialize result tuple type and projection info.  The node's
	 * targetlist will contain Vars with varno = INDEX_VAR, referencing the
	 * scan tuple.
	 */
	ExecAssignResultTypeFromTL(&indexstate->ss.ps);
	ExecAssignScanProjectionInfoWithVarno(&indexstate->ss, INDEX_VAR);

	/*
	 * If we are just doing EXPLAIN (ie, aren't going to run the plan), stop
	 * here.  This allows an index-advisor plugin to EXPLAIN a plan containing
	 * references to nonexistent indexes.
	 */
	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
		return indexstate;

	/*
	 * Open the index relation.
	 *
	 * If the parent table is one of the target relations of the query, then
	 * InitPlan already opened and write-locked the index, so we can avoid
	 * taking another lock here.  Otherwise we need a normal reader's lock.
	 */
	relistarget = ExecRelationIsTargetRelation(estate, node->scan.scanrelid);
//.........这里部分代码省略.........

CustomScanState *
ExecInitCustomScan(CustomScan *cscan, EState *estate, int eflags)
{
	CustomScanState *css;
	Relation	scan_rel = NULL;
	Index		scanrelid = cscan->scan.scanrelid;
	Index		tlistvarno;

	/*
	 * Allocate the CustomScanState object.  We let the custom scan provider
	 * do the palloc, in case it wants to make a larger object that embeds
	 * CustomScanState as the first field.  It must set the node tag and the
	 * methods field correctly at this time.  Other standard fields should be
	 * set to zero.
	 */
	css = (CustomScanState *) cscan->methods->CreateCustomScanState(cscan);
	Assert(IsA(css, CustomScanState));

	/* ensure flags is filled correctly */
	css->flags = cscan->flags;

	/* fill up fields of ScanState */
	css->ss.ps.plan = &cscan->scan.plan;
	css->ss.ps.state = estate;

	/* create expression context for node */
	ExecAssignExprContext(estate, &css->ss.ps);
#ifdef PG95
	css->ss.ps.ps_TupFromTlist = false;
#endif
	/* initialize child expressions */
	css->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) cscan->scan.plan.targetlist,
					 (PlanState *) css);
	css->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) cscan->scan.plan.qual,
					 (PlanState *) css);

	/* tuple table initialization */
#ifndef PG95
	if (((Scan*)css->ss.ps.plan)->scanrelid) {
		// For table scans
		ExecInitScanTupleSlot(estate, &css->ss);
	}
	else {
		// For tuple-table-slot scans (typically over Motion nodes)
		css->ss.ss_ScanTupleSlot = ExecAllocTableSlot(&estate->es_tupleTable);
	}
#else
	ExecInitScanTupleSlot(estate, &css->ss);
#endif
	ExecInitResultTupleSlot(estate, &css->ss.ps);

	/*
	 * open the base relation, if any, and acquire an appropriate lock on it
	 */
	if (scanrelid > 0)
	{
		scan_rel = ExecOpenScanRelation(estate
										, scanrelid
#ifdef PG95
										, eflags
#endif
		);
		css->ss.ss_currentRelation = scan_rel;
	}

	/*
	 * Determine the scan tuple type.  If the custom scan provider provided a
	 * targetlist describing the scan tuples, use that; else use base
	 * relation's rowtype.
	 */
	if (cscan->custom_scan_tlist != NIL || scan_rel == NULL)
	{

		// index-only scan? GP doesn't define INDEX_VAR
		TupleDesc	scan_tupdesc;

		scan_tupdesc = ExecTypeFromTL(cscan->custom_scan_tlist, false);
		ExecAssignScanType(&css->ss, scan_tupdesc);

#ifdef PG95
		/* Node's targetlist will contain Vars with varno = INDEX_VAR */
		tlistvarno = INDEX_VAR;
#endif
	}
	else
	{
		ExecAssignScanType(&css->ss, RelationGetDescr(scan_rel));
		/* Node's targetlist will contain Vars with varno = scanrelid */
		tlistvarno = scanrelid;
	}

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&css->ss.ps);
#ifdef PG95
	ExecAssignScanProjectionInfoWithVarno(&css->ss, tlistvarno);
#else
//.........这里部分代码省略.........

/* ----------------------------------------------------------------
 *		ExecInitIndexScan
 *
 *		Initializes the index scan's state information, creates
 *		scan keys, and opens the base and index relations.
 *
 *		Note: index scans have 2 sets of state information because
 *			  we have to keep track of the base relation and the
 *			  index relation.
 * ----------------------------------------------------------------
 */
IndexScanState *
ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
{
    IndexScanState *indexstate;
    Relation	currentRelation;
    bool		relistarget;

    /*
     * create state structure
     */
    indexstate = makeNode(IndexScanState);
    indexstate->ss.ps.plan = (Plan *) node;
    indexstate->ss.ps.state = estate;

    /*
     * Miscellaneous initialization
     *
     * create expression context for node
     */
    ExecAssignExprContext(estate, &indexstate->ss.ps);

    /*indexstate->ss.ps.ps_TupFromTlist = false;*/

    /*
     * initialize child expressions
     *
     * Note: we don't initialize all of the indexqual expression, only the
     * sub-parts corresponding to runtime keys (see below).  The indexqualorig
     * expression is always initialized even though it will only be used in
     * some uncommon cases --- would be nice to improve that.  (Problem is
     * that any SubPlans present in the expression must be found now...)
     */
    indexstate->ss.ps.targetlist = (List *)
                                   ExecInitExpr((Expr *) node->scan.plan.targetlist,
                                           (PlanState *) indexstate);
    indexstate->ss.ps.qual = (List *)
                             ExecInitExpr((Expr *) node->scan.plan.qual,
                                          (PlanState *) indexstate);
    indexstate->indexqualorig = (List *)
                                ExecInitExpr((Expr *) node->indexqualorig,
                                        (PlanState *) indexstate);

#define INDEXSCAN_NSLOTS 2

    /*
     * tuple table initialization
     */
    ExecInitResultTupleSlot(estate, &indexstate->ss.ps);
    ExecInitScanTupleSlot(estate, &indexstate->ss);

    /*
     * open the base relation and acquire appropriate lock on it.
     */
    currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);

    indexstate->ss.ss_currentRelation = currentRelation;

    /*
     * get the scan type from the relation descriptor.
     */
    ExecAssignScanType(&indexstate->ss, RelationGetDescr(currentRelation));

    /*
     * Open the index relation.
     *
     * If the parent table is one of the target relations of the query, then
     * InitPlan already opened and write-locked the index, so we can avoid
     * taking another lock here.  Otherwise we need a normal reader's lock.
     */
    relistarget = ExecRelationIsTargetRelation(estate, node->scan.scanrelid);
    indexstate->iss_RelationDesc = index_open(node->indexid,
                                   relistarget ? NoLock : AccessShareLock);

    /*
     * build the index scan keys from the index qualification
     */
    ExecIndexBuildScanKeys((PlanState *) indexstate,
                           indexstate->iss_RelationDesc,
                           node->indexqual,
                           node->indexstrategy,
                           node->indexsubtype,
                           &indexstate->iss_ScanKeys,
                           &indexstate->iss_NumScanKeys,
                           &indexstate->iss_RuntimeKeys,
                           &indexstate->iss_NumRuntimeKeys,
                           NULL,	/* no ArrayKeys */
                           NULL);

    /*
//.........这里部分代码省略.........

/* ----------------------------------------------------------------
 *		ExecInitBitmapHeapScan
 *
 *		Initializes the scan's state information.
 * ----------------------------------------------------------------
 */
BitmapHeapScanState *
ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
{
	BitmapHeapScanState *scanstate;
	Relation	currentRelation;

	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * Assert caller didn't ask for an unsafe snapshot --- see comments at
	 * head of file.
	 */
	Assert(IsMVCCSnapshot(estate->es_snapshot));

	/*
	 * create state structure
	 */
	scanstate = makeNode(BitmapHeapScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;

	scanstate->tbm = NULL;
	scanstate->tbmiterator = NULL;
	scanstate->tbmres = NULL;
	scanstate->prefetch_iterator = NULL;
	scanstate->prefetch_pages = 0;
	scanstate->prefetch_target = 0;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	scanstate->ss.ps.ps_TupFromTlist = false;

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) scanstate);
	scanstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) scanstate);
	scanstate->bitmapqualorig = (List *)
		ExecInitExpr((Expr *) node->bitmapqualorig,
					 (PlanState *) scanstate);

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
	ExecInitScanTupleSlot(estate, &scanstate->ss);

	/*
	 * open the base relation and acquire appropriate lock on it.
	 */
	currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);

	scanstate->ss.ss_currentRelation = currentRelation;

	/*
	 * Even though we aren't going to do a conventional seqscan, it is useful
	 * to create a HeapScanDesc --- most of the fields in it are usable.
	 */
	scanstate->ss.ss_currentScanDesc = heap_beginscan_bm(currentRelation,
														 estate->es_snapshot,
														 0,
														 NULL);

	/*
	 * get the scan type from the relation descriptor.
	 */
	ExecAssignScanType(&scanstate->ss, RelationGetDescr(currentRelation));

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
	ExecAssignScanProjectionInfo(&scanstate->ss);

	/*
	 * initialize child nodes
	 *
	 * We do this last because the child nodes will open indexscans on our
	 * relation's indexes, and we want to be sure we have acquired a lock on
	 * the relation first.
	 */
	outerPlanState(scanstate) = ExecInitNode(outerPlan(node), estate, eflags);

	/*
//.........这里部分代码省略.........

/* ----------------------------------------------------------------
 *		ExecInitSubqueryScan
 * ----------------------------------------------------------------
 */
SubqueryScanState *
ExecInitSubqueryScan(SubqueryScan *node, EState *estate, int eflags)
{
	SubqueryScanState *subquerystate;

	/* check for unsupported flags */
	Assert(!(eflags & EXEC_FLAG_MARK));

	/* SubqueryScan should not have any "normal" children */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create state structure
	 */
	subquerystate = makeNode(SubqueryScanState);
	subquerystate->ss.ps.plan = (Plan *) node;
	subquerystate->ss.ps.state = estate;
	subquerystate->ss.ps.ExecProcNode = ExecSubqueryScan;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &subquerystate->ss.ps);

	/*
	 * initialize subquery
	 */
	subquerystate->subplan = ExecInitNode(node->subplan, estate, eflags);

	/*
	 * Initialize scan slot and type (needed by ExecAssignScanProjectionInfo)
	 */
	ExecInitScanTupleSlot(estate, &subquerystate->ss,
						  ExecGetResultType(subquerystate->subplan),
						  ExecGetResultSlotOps(subquerystate->subplan, NULL));
	/*
	 * The slot used as the scantuple isn't the slot above (outside of EPQ),
	 * but the one from the node below.
	 */
	subquerystate->ss.ps.scanopsset = true;
	subquerystate->ss.ps.scanops = ExecGetResultSlotOps(subquerystate->subplan,
														&subquerystate->ss.ps.scanopsfixed);
	subquerystate->ss.ps.resultopsset = true;
	subquerystate->ss.ps.resultops = subquerystate->ss.ps.scanops;
	subquerystate->ss.ps.resultopsfixed = subquerystate->ss.ps.scanopsfixed;

	/*
	 * Initialize result type and projection.
	 */
	ExecInitResultTypeTL(&subquerystate->ss.ps);
	ExecAssignScanProjectionInfo(&subquerystate->ss);

	/*
	 * initialize child expressions
	 */
	subquerystate->ss.ps.qual =
		ExecInitQual(node->scan.plan.qual, (PlanState *) subquerystate);

	return subquerystate;
}

/* ----------------------------------------------------------------
 *		ExecInitMaterial
 * ----------------------------------------------------------------
 */
MaterialState *
ExecInitMaterial(Material *node, EState *estate, int eflags)
{
	MaterialState *matstate;
	Plan	   *outerPlan;

	/*
	 * create state structure
	 */
	matstate = makeNode(MaterialState);
	matstate->ss.ps.plan = (Plan *) node;
	matstate->ss.ps.state = estate;

	/*
	 * We must have random access to the subplan output to do backward scan
	 * or mark/restore.  We also prefer to materialize the subplan output
	 * if we might be called on to rewind and replay it many times.
	 * However, if none of these cases apply, we can skip storing the data.
	 */
	matstate->randomAccess = (eflags & (EXEC_FLAG_REWIND |
										EXEC_FLAG_BACKWARD |
										EXEC_FLAG_MARK)) != 0;

	matstate->eof_underlying = false;
	matstate->tuplestorestate = NULL;

	/*
	 * Miscellaneous initialization
	 *
	 * Materialization nodes don't need ExprContexts because they never call
	 * ExecQual or ExecProject.
	 */

#define MATERIAL_NSLOTS 2

	/*
	 * tuple table initialization
	 *
	 * material nodes only return tuples from their materialized relation.
	 */
	ExecInitResultTupleSlot(estate, &matstate->ss.ps);
	ExecInitScanTupleSlot(estate, &matstate->ss);

	/*
	 * initialize child nodes
	 *
	 * We shield the child node from the need to support REWIND, BACKWARD,
	 * or MARK/RESTORE.
	 */
	eflags &= ~(EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK);

	outerPlan = outerPlan(node);
	outerPlanState(matstate) = ExecInitNode(outerPlan, estate, eflags);

	/*
	 * initialize tuple type.  no need to initialize projection info because
	 * this node doesn't do projections.
	 */
	ExecAssignResultTypeFromTL(&matstate->ss.ps);
	ExecAssignScanTypeFromOuterPlan(&matstate->ss);
	matstate->ss.ps.ps_ProjInfo = NULL;

	return matstate;
}

//.........这里部分代码省略.........
	 * Note: if we are in an EPQ recheck plan tree, it's likely that no access
	 * to the tuplestore is needed at all, making this even more annoying.
	 * It's not worth improving that as long as all the read pointers would
	 * have REWIND anyway, but if we ever improve this logic then that aspect
	 * should be considered too.
	 */
	eflags |= EXEC_FLAG_REWIND;

	/*
	 * CteScan should not have any children.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create new CteScanState for node
	 */
	scanstate = makeNode(CteScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->eflags = eflags;
	scanstate->cte_table = NULL;
	scanstate->eof_cte = false;

	/*
	 * Find the already-initialized plan for the CTE query.
	 */
	scanstate->cteplanstate = (PlanState *) list_nth(estate->es_subplanstates,
													 node->ctePlanId - 1);

	/*
	 * The Param slot associated with the CTE query is used to hold a pointer
	 * to the CteState of the first CteScan node that initializes for this
	 * CTE.  This node will be the one that holds the shared state for all the
	 * CTEs, particularly the shared tuplestore.
	 */
	prmdata = &(estate->es_param_exec_vals[node->cteParam]);
	Assert(prmdata->execPlan == NULL);
	Assert(!prmdata->isnull);
	scanstate->leader = (CteScanState *) DatumGetPointer(prmdata->value);
	if (scanstate->leader == NULL)
	{
		/* I am the leader */
		prmdata->value = PointerGetDatum(scanstate);
		scanstate->leader = scanstate;
		scanstate->cte_table = tuplestore_begin_heap(true, false, work_mem);
		tuplestore_set_eflags(scanstate->cte_table, scanstate->eflags);
		scanstate->readptr = 0;
	}
	else
	{
		/* Not the leader */
		Assert(IsA(scanstate->leader, CteScanState));
		/* Create my own read pointer, and ensure it is at start */
		scanstate->readptr =
			tuplestore_alloc_read_pointer(scanstate->leader->cte_table,
										  scanstate->eflags);
		tuplestore_select_read_pointer(scanstate->leader->cte_table,
									   scanstate->readptr);
		tuplestore_rescan(scanstate->leader->cte_table);
	}

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) scanstate);
	scanstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) scanstate);

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
	ExecInitScanTupleSlot(estate, &scanstate->ss);

	/*
	 * The scan tuple type (ie, the rowtype we expect to find in the work
	 * table) is the same as the result rowtype of the CTE query.
	 */
	ExecAssignScanType(&scanstate->ss,
					   ExecGetResultType(scanstate->cteplanstate));

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
	ExecAssignScanProjectionInfo(&scanstate->ss);

	return scanstate;
}

/* ----------------------------------------------------------------
 *		ExecInitFunctionScan
 * ----------------------------------------------------------------
 */
FunctionScanState *
ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
{
	FunctionScanState *scanstate;
	Oid			funcrettype;
	TypeFuncClass functypclass;
	TupleDesc	tupdesc = NULL;

	/* check for unsupported flags */
	Assert(!(eflags & EXEC_FLAG_MARK));

	/*
	 * FunctionScan should not have any children.
	 */
	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create new ScanState for node
	 */
	scanstate = makeNode(FunctionScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->eflags = eflags;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
	ExecInitScanTupleSlot(estate, &scanstate->ss);

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) scanstate);
	scanstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) scanstate);

	/*
	 * Now determine if the function returns a simple or composite type, and
	 * build an appropriate tupdesc.
	 */
	functypclass = get_expr_result_type(node->funcexpr,
										&funcrettype,
										&tupdesc);

	if (functypclass == TYPEFUNC_COMPOSITE)
	{
		/* Composite data type, e.g. a table's row type */
		Assert(tupdesc);
		/* Must copy it out of typcache for safety */
		tupdesc = CreateTupleDescCopy(tupdesc);
	}
	else if (functypclass == TYPEFUNC_SCALAR)
	{
		/* Base data type, i.e. scalar */
		char	   *attname = strVal(linitial(node->funccolnames));

		tupdesc = CreateTemplateTupleDesc(1, false);
		TupleDescInitEntry(tupdesc,
						   (AttrNumber) 1,
						   attname,
						   funcrettype,
						   -1,
						   0);
	}
	else if (functypclass == TYPEFUNC_RECORD)
	{
		tupdesc = BuildDescFromLists(node->funccolnames,
									 node->funccoltypes,
									 node->funccoltypmods);
	}
	else
	{
		/* crummy error message, but parser should have caught this */
		elog(ERROR, "function in FROM has unsupported return type");
	}

	/*
	 * For RECORD results, make sure a typmod has been assigned.  (The
	 * function should do this for itself, but let's cover things in case it
	 * doesn't.)
	 */
	BlessTupleDesc(tupdesc);

	scanstate->tupdesc = tupdesc;
//.........这里部分代码省略.........

/* ----------------------------------------------------------------
 *		ExecInitBitmapHeapScan
 *
 *		Initializes the scan's state information.
 * ----------------------------------------------------------------
 */
BitmapHeapScanState *
ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
{
	BitmapHeapScanState *scanstate;
	Relation	currentRelation;

	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

	/*
	 * Assert caller didn't ask for an unsafe snapshot --- see comments at
	 * head of file.
	 */
	Assert(IsMVCCSnapshot(estate->es_snapshot));

	/*
	 * create state structure
	 */
	scanstate = makeNode(BitmapHeapScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;

	scanstate->tbm = NULL;
	scanstate->tbmres = NULL;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &scanstate->ss.ps);

	scanstate->ss.ps.ps_TupFromTlist = false;

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) scanstate);
	scanstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) scanstate);
	scanstate->bitmapqualorig = (List *)
		ExecInitExpr((Expr *) node->bitmapqualorig,
					 (PlanState *) scanstate);

#define BITMAPHEAPSCAN_NSLOTS 2

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &scanstate->