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+/*-------------------------------------------------------------------------
+ * execScan.h
+ * Inline-able support functions for Scan nodes
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * src/include/executor/execScan.h
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef EXECSCAN_H
+#define EXECSCAN_H
+
+#include "miscadmin.h"
+#include "executor/executor.h"
+#include "nodes/execnodes.h"
+
+/*
+ * ExecScanFetch -- check interrupts & fetch next potential tuple
+ *
+ * This routine substitutes a test tuple if inside an EvalPlanQual recheck.
+ * Otherwise, it simply executes the access method's next-tuple routine.
+ *
+ * The pg_attribute_always_inline attribute allows the compiler to inline
+ * this function into its caller. When EPQState is NULL, the EvalPlanQual
+ * logic is completely eliminated at compile time, avoiding unnecessary
+ * run-time checks and code for cases where EPQ is not required.
+ */
+static pg_attribute_always_inline TupleTableSlot *
+ExecScanFetch(ScanState *node,
+ EPQState *epqstate,
+ ExecScanAccessMtd accessMtd,
+ ExecScanRecheckMtd recheckMtd)
+{
+ CHECK_FOR_INTERRUPTS();
+
+ if (epqstate != NULL)
+ {
+ /*
+ * We are inside an EvalPlanQual recheck. Return the test tuple if
+ * one is available, after rechecking any access-method-specific
+ * conditions.
+ */
+ Index scanrelid = ((Scan *) node->ps.plan)->scanrelid;
+
+ if (scanrelid == 0)
+ {
+ /*
+ * This is a ForeignScan or CustomScan which has pushed down a
+ * join to the remote side. The recheck method is responsible not
+ * only for rechecking the scan/join quals but also for storing
+ * the correct tuple in the slot.
+ */
+
+ TupleTableSlot *slot = node->ss_ScanTupleSlot;
+
+ if (!(*recheckMtd) (node, slot))
+ ExecClearTuple(slot); /* would not be returned by scan */
+ return slot;
+ }
+ else if (epqstate->relsubs_done[scanrelid - 1])
+ {
+ /*
+ * Return empty slot, as either there is no EPQ tuple for this rel
+ * or we already returned it.
+ */
+
+ TupleTableSlot *slot = node->ss_ScanTupleSlot;
+
+ return ExecClearTuple(slot);
+ }
+ else if (epqstate->relsubs_slot[scanrelid - 1] != NULL)
+ {
+ /*
+ * Return replacement tuple provided by the EPQ caller.
+ */
+
+ TupleTableSlot *slot = epqstate->relsubs_slot[scanrelid - 1];
+
+ Assert(epqstate->relsubs_rowmark[scanrelid - 1] == NULL);
+
+ /* Mark to remember that we shouldn't return it again */
+ epqstate->relsubs_done[scanrelid - 1] = true;
+
+ /* Return empty slot if we haven't got a test tuple */
+ if (TupIsNull(slot))
+ return NULL;
+
+ /* Check if it meets the access-method conditions */
+ if (!(*recheckMtd) (node, slot))
+ return ExecClearTuple(slot); /* would not be returned by
+ * scan */
+ return slot;
+ }
+ else if (epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
+ {
+ /*
+ * Fetch and return replacement tuple using a non-locking rowmark.
+ */
+
+ TupleTableSlot *slot = node->ss_ScanTupleSlot;
+
+ /* Mark to remember that we shouldn't return more */
+ epqstate->relsubs_done[scanrelid - 1] = true;
+
+ if (!EvalPlanQualFetchRowMark(epqstate, scanrelid, slot))
+ return NULL;
+
+ /* Return empty slot if we haven't got a test tuple */
+ if (TupIsNull(slot))
+ return NULL;
+
+ /* Check if it meets the access-method conditions */
+ if (!(*recheckMtd) (node, slot))
+ return ExecClearTuple(slot); /* would not be returned by
+ * scan */
+ return slot;
+ }
+ }
+
+ /*
+ * Run the node-type-specific access method function to get the next tuple
+ */
+ return (*accessMtd) (node);
+}
+
+/* ----------------------------------------------------------------
+ * ExecScanExtended
+ * Scans the relation using the specified 'access method' and returns the
+ * next tuple. Optionally checks the tuple against 'qual' and applies
+ * 'projInfo' if provided.
+ *
+ * The 'recheck method' validates an arbitrary tuple of the relation against
+ * conditions enforced by the access method.
+ *
+ * This function is an alternative to ExecScan, used when callers may omit
+ * 'qual' or 'projInfo'. The pg_attribute_always_inline attribute allows the
+ * compiler to eliminate non-relevant branches at compile time, avoiding
+ * run-time checks in those cases.
+ *
+ * Conditions:
+ * -- The AMI "cursor" is positioned at the previously returned tuple.
+ *
+ * Initial States:
+ * -- The relation is opened for scanning, with the "cursor"
+ * positioned before the first qualifying tuple.
+ * ----------------------------------------------------------------
+ */
+static pg_attribute_always_inline TupleTableSlot *
+ExecScanExtended(ScanState *node,
+ ExecScanAccessMtd accessMtd, /* function returning a tuple */
+ ExecScanRecheckMtd recheckMtd,
+ EPQState *epqstate,
+ ExprState *qual,
+ ProjectionInfo *projInfo)
+{
+ ExprContext *econtext = node->ps.ps_ExprContext;
+
+ /* interrupt checks are in ExecScanFetch */
+
+ /*
+ * If we have neither a qual to check nor a projection to do, just skip
+ * all the overhead and return the raw scan tuple.
+ */
+ if (!qual && !projInfo)
+ {
+ ResetExprContext(econtext);
+ return ExecScanFetch(node, epqstate, accessMtd, recheckMtd);
+ }
+
+ /*
+ * Reset per-tuple memory context to free any expression evaluation
+ * storage allocated in the previous tuple cycle.
+ */
+ ResetExprContext(econtext);
+
+ /*
+ * get a tuple from the access method. Loop until we obtain a tuple that
+ * passes the qualification.
+ */
+ for (;;)
+ {
+ TupleTableSlot *slot;
+
+ slot = ExecScanFetch(node, epqstate, accessMtd, recheckMtd);
+
+ /*
+ * if the slot returned by the accessMtd contains NULL, then it means
+ * there is nothing more to scan so we just return an empty slot,
+ * being careful to use the projection result slot so it has correct
+ * tupleDesc.
+ */
+ if (TupIsNull(slot))
+ {
+ if (projInfo)
+ return ExecClearTuple(projInfo->pi_state.resultslot);
+ else
+ return slot;
+ }
+
+ /*
+ * place the current tuple into the expr context
+ */
+ econtext->ecxt_scantuple = slot;
+
+ /*
+ * check that the current tuple satisfies the qual-clause
+ *
+ * check for non-null qual here to avoid a function call to ExecQual()
+ * when the qual is null ... saves only a few cycles, but they add up
+ * ...
+ */
+ if (qual == NULL || ExecQual(qual, econtext))
+ {
+ /*
+ * Found a satisfactory scan tuple.
+ */
+ if (projInfo)
+ {
+ /*
+ * Form a projection tuple, store it in the result tuple slot
+ * and return it.
+ */
+ return ExecProject(projInfo);
+ }
+ else
+ {
+ /*
+ * Here, we aren't projecting, so just return scan tuple.
+ */
+ return slot;
+ }
+ }
+ else
+ InstrCountFiltered1(node, 1);
+
+ /*
+ * Tuple fails qual, so free per-tuple memory and try again.
+ */
+ ResetExprContext(econtext);
+ }
+}
+
+#endif /* EXECSCAN_H */