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Diffstat (limited to 'src/include/executor/execScan.h')
-rw-r--r-- | src/include/executor/execScan.h | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/src/include/executor/execScan.h b/src/include/executor/execScan.h new file mode 100644 index 00000000000..837ea7785bb --- /dev/null +++ b/src/include/executor/execScan.h @@ -0,0 +1,246 @@ +/*------------------------------------------------------------------------- + * 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 */ |