1 files changed, 413 insertions, 0 deletions
diff --git a/src/backend/executor/nodeTidrangescan.c b/src/backend/executor/nodeTidrangescan.c
new file mode 100644
index 0000000..d5bf1be
--- /dev/null
+++ b/src/backend/executor/nodeTidrangescan.c
@@ -0,0 +1,413 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeTidrangescan.c
+ *	  Routines to support TID range scans of relations
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeTidrangescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "access/sysattr.h"
+#include "access/tableam.h"
+#include "catalog/pg_operator.h"
+#include "executor/execdebug.h"
+#include "executor/nodeTidrangescan.h"
+#include "nodes/nodeFuncs.h"
+#include "storage/bufmgr.h"
+#include "utils/rel.h"
+
+
+#define IsCTIDVar(node)  \
+	((node) != NULL && \
+	 IsA((node), Var) && \
+	 ((Var *) (node))->varattno == SelfItemPointerAttributeNumber && \
+	 ((Var *) (node))->varlevelsup == 0)
+
+typedef enum
+{
+	TIDEXPR_UPPER_BOUND,
+	TIDEXPR_LOWER_BOUND
+} TidExprType;
+
+/* Upper or lower range bound for scan */
+typedef struct TidOpExpr
+{
+	TidExprType exprtype;		/* type of op; lower or upper */
+	ExprState  *exprstate;		/* ExprState for a TID-yielding subexpr */
+	bool		inclusive;		/* whether op is inclusive */
+} TidOpExpr;
+
+/*
+ * For the given 'expr', build and return an appropriate TidOpExpr taking into
+ * account the expr's operator and operand order.
+ */
+static TidOpExpr *
+MakeTidOpExpr(OpExpr *expr, TidRangeScanState *tidstate)
+{
+	Node	   *arg1 = get_leftop((Expr *) expr);
+	Node	   *arg2 = get_rightop((Expr *) expr);
+	ExprState  *exprstate = NULL;
+	bool		invert = false;
+	TidOpExpr  *tidopexpr;
+
+	if (IsCTIDVar(arg1))
+		exprstate = ExecInitExpr((Expr *) arg2, &tidstate->ss.ps);
+	else if (IsCTIDVar(arg2))
+	{
+		exprstate = ExecInitExpr((Expr *) arg1, &tidstate->ss.ps);
+		invert = true;
+	}
+	else
+		elog(ERROR, "could not identify CTID variable");
+
+	tidopexpr = (TidOpExpr *) palloc(sizeof(TidOpExpr));
+	tidopexpr->inclusive = false;	/* for now */
+
+	switch (expr->opno)
+	{
+		case TIDLessEqOperator:
+			tidopexpr->inclusive = true;
+			/* fall through */
+		case TIDLessOperator:
+			tidopexpr->exprtype = invert ? TIDEXPR_LOWER_BOUND : TIDEXPR_UPPER_BOUND;
+			break;
+		case TIDGreaterEqOperator:
+			tidopexpr->inclusive = true;
+			/* fall through */
+		case TIDGreaterOperator:
+			tidopexpr->exprtype = invert ? TIDEXPR_UPPER_BOUND : TIDEXPR_LOWER_BOUND;
+			break;
+		default:
+			elog(ERROR, "could not identify CTID operator");
+	}
+
+	tidopexpr->exprstate = exprstate;
+
+	return tidopexpr;
+}
+
+/*
+ * Extract the qual subexpressions that yield TIDs to search for,
+ * and compile them into ExprStates if they're ordinary expressions.
+ */
+static void
+TidExprListCreate(TidRangeScanState *tidrangestate)
+{
+	TidRangeScan *node = (TidRangeScan *) tidrangestate->ss.ps.plan;
+	List	   *tidexprs = NIL;
+	ListCell   *l;
+
+	foreach(l, node->tidrangequals)
+	{
+		OpExpr	   *opexpr = lfirst(l);
+		TidOpExpr  *tidopexpr;
+
+		if (!IsA(opexpr, OpExpr))
+			elog(ERROR, "could not identify CTID expression");
+
+		tidopexpr = MakeTidOpExpr(opexpr, tidrangestate);
+		tidexprs = lappend(tidexprs, tidopexpr);
+	}
+
+	tidrangestate->trss_tidexprs = tidexprs;
+}
+
+/* ----------------------------------------------------------------
+ *		TidRangeEval
+ *
+ *		Compute and set node's block and offset range to scan by evaluating
+ *		the trss_tidexprs.  Returns false if we detect the range cannot
+ *		contain any tuples.  Returns true if it's possible for the range to
+ *		contain tuples.
+ * ----------------------------------------------------------------
+ */
+static bool
+TidRangeEval(TidRangeScanState *node)
+{
+	ExprContext *econtext = node->ss.ps.ps_ExprContext;
+	ItemPointerData lowerBound;
+	ItemPointerData upperBound;
+	ListCell   *l;
+
+	/*
+	 * Set the upper and lower bounds to the absolute limits of the range of
+	 * the ItemPointer type.  Below we'll try to narrow this range on either
+	 * side by looking at the TidOpExprs.
+	 */
+	ItemPointerSet(&lowerBound, 0, 0);
+	ItemPointerSet(&upperBound, InvalidBlockNumber, PG_UINT16_MAX);
+
+	foreach(l, node->trss_tidexprs)
+	{
+		TidOpExpr  *tidopexpr = (TidOpExpr *) lfirst(l);
+		ItemPointer itemptr;
+		bool		isNull;
+
+		/* Evaluate this bound. */
+		itemptr = (ItemPointer)
+			DatumGetPointer(ExecEvalExprSwitchContext(tidopexpr->exprstate,
+													  econtext,
+													  &isNull));
+
+		/* If the bound is NULL, *nothing* matches the qual. */
+		if (isNull)
+			return false;
+
+		if (tidopexpr->exprtype == TIDEXPR_LOWER_BOUND)
+		{
+			ItemPointerData lb;
+
+			ItemPointerCopy(itemptr, &lb);
+
+			/*
+			 * Normalize non-inclusive ranges to become inclusive.  The
+			 * resulting ItemPointer here may not be a valid item pointer.
+			 */
+			if (!tidopexpr->inclusive)
+				ItemPointerInc(&lb);
+
+			/* Check if we can narrow the range using this qual */
+			if (ItemPointerCompare(&lb, &lowerBound) > 0)
+				ItemPointerCopy(&lb, &lowerBound);
+		}
+
+		else if (tidopexpr->exprtype == TIDEXPR_UPPER_BOUND)
+		{
+			ItemPointerData ub;
+
+			ItemPointerCopy(itemptr, &ub);
+
+			/*
+			 * Normalize non-inclusive ranges to become inclusive.  The
+			 * resulting ItemPointer here may not be a valid item pointer.
+			 */
+			if (!tidopexpr->inclusive)
+				ItemPointerDec(&ub);
+
+			/* Check if we can narrow the range using this qual */
+			if (ItemPointerCompare(&ub, &upperBound) < 0)
+				ItemPointerCopy(&ub, &upperBound);
+		}
+	}
+
+	ItemPointerCopy(&lowerBound, &node->trss_mintid);
+	ItemPointerCopy(&upperBound, &node->trss_maxtid);
+
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		TidRangeNext
+ *
+ *		Retrieve a tuple from the TidRangeScan node's currentRelation
+ *		using the TIDs in the TidRangeScanState information.
+ *
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+TidRangeNext(TidRangeScanState *node)
+{
+	TableScanDesc scandesc;
+	EState	   *estate;
+	ScanDirection direction;
+	TupleTableSlot *slot;
+
+	/*
+	 * extract necessary information from TID scan node
+	 */
+	scandesc = node->ss.ss_currentScanDesc;
+	estate = node->ss.ps.state;
+	slot = node->ss.ss_ScanTupleSlot;
+	direction = estate->es_direction;
+
+	if (!node->trss_inScan)
+	{
+		/* First time through, compute TID range to scan */
+		if (!TidRangeEval(node))
+			return NULL;
+
+		if (scandesc == NULL)
+		{
+			scandesc = table_beginscan_tidrange(node->ss.ss_currentRelation,
+												estate->es_snapshot,
+												&node->trss_mintid,
+												&node->trss_maxtid);
+			node->ss.ss_currentScanDesc = scandesc;
+		}
+		else
+		{
+			/* rescan with the updated TID range */
+			table_rescan_tidrange(scandesc, &node->trss_mintid,
+								  &node->trss_maxtid);
+		}
+
+		node->trss_inScan = true;
+	}
+
+	/* Fetch the next tuple. */
+	if (!table_scan_getnextslot_tidrange(scandesc, direction, slot))
+	{
+		node->trss_inScan = false;
+		ExecClearTuple(slot);
+	}
+
+	return slot;
+}
+
+/*
+ * TidRangeRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+TidRangeRecheck(TidRangeScanState *node, TupleTableSlot *slot)
+{
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecTidRangeScan(node)
+ *
+ *		Scans the relation using tids and returns the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ *
+ *		Conditions:
+ *		  -- the "cursor" maintained by the AMI is positioned at the tuple
+ *			 returned previously.
+ *
+ *		Initial States:
+ *		  -- the relation indicated is opened for TID range scanning.
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+ExecTidRangeScan(PlanState *pstate)
+{
+	TidRangeScanState *node = castNode(TidRangeScanState, pstate);
+
+	return ExecScan(&node->ss,
+					(ExecScanAccessMtd) TidRangeNext,
+					(ExecScanRecheckMtd) TidRangeRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecReScanTidRangeScan(node)
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanTidRangeScan(TidRangeScanState *node)
+{
+	/* mark scan as not in progress, and tid range list as not computed yet */
+	node->trss_inScan = false;
+
+	/*
+	 * We must wait until TidRangeNext before calling table_rescan_tidrange.
+	 */
+	ExecScanReScan(&node->ss);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndTidRangeScan
+ *
+ *		Releases any storage allocated through C routines.
+ *		Returns nothing.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndTidRangeScan(TidRangeScanState *node)
+{
+	TableScanDesc scan = node->ss.ss_currentScanDesc;
+
+	if (scan != NULL)
+		table_endscan(scan);
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clear out tuple table slots
+	 */
+	if (node->ss.ps.ps_ResultTupleSlot)
+		ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecInitTidRangeScan
+ *
+ *		Initializes the tid range scan's state information, creates
+ *		scan keys, and opens the scan relation.
+ *
+ *		Parameters:
+ *		  node: TidRangeScan node produced by the planner.
+ *		  estate: the execution state initialized in InitPlan.
+ * ----------------------------------------------------------------
+ */
+TidRangeScanState *
+ExecInitTidRangeScan(TidRangeScan *node, EState *estate, int eflags)
+{
+	TidRangeScanState *tidrangestate;
+	Relation	currentRelation;
+
+	/*
+	 * create state structure
+	 */
+	tidrangestate = makeNode(TidRangeScanState);
+	tidrangestate->ss.ps.plan = (Plan *) node;
+	tidrangestate->ss.ps.state = estate;
+	tidrangestate->ss.ps.ExecProcNode = ExecTidRangeScan;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &tidrangestate->ss.ps);
+
+	/*
+	 * mark scan as not in progress, and TID range as not computed yet
+	 */
+	tidrangestate->trss_inScan = false;
+
+	/*
+	 * open the scan relation
+	 */
+	currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
+
+	tidrangestate->ss.ss_currentRelation = currentRelation;
+	tidrangestate->ss.ss_currentScanDesc = NULL;	/* no table scan here */
+
+	/*
+	 * get the scan type from the relation descriptor.
+	 */
+	ExecInitScanTupleSlot(estate, &tidrangestate->ss,
+						  RelationGetDescr(currentRelation),
+						  table_slot_callbacks(currentRelation));
+
+	/*
+	 * Initialize result type and projection.
+	 */
+	ExecInitResultTypeTL(&tidrangestate->ss.ps);
+	ExecAssignScanProjectionInfo(&tidrangestate->ss);
+
+	/*
+	 * initialize child expressions
+	 */
+	tidrangestate->ss.ps.qual =
+		ExecInitQual(node->scan.plan.qual, (PlanState *) tidrangestate);
+
+	TidExprListCreate(tidrangestate);
+
+	/*
+	 * all done.
+	 */
+	return tidrangestate;
+}