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Pass down information on table modification to scan nodes

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Pass down information to sequential scan, index [only] scan, bitmap
table scan, sample scan, and TID range scan nodes on whether or not the
query modifies the relation being scanned. A later commit will use this
information to update the VM during on-access pruning only if the
relation is not modified by the query.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Tomas Vondra <tomas@vondra.me>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/4379FDA3-9446-4E2C-9C15-32EFE8D4F31B%40yandex-team.ru
This commit is contained in:
Melanie Plageman 2026-03-30 13:27:34 -04:00
parent 349bd88202
commit 50eb5faea2
9 changed files with 59 additions and 15 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

21
src/backend/executor/execUtils.c
View file

@ -736,6 +736,27 @@ ExecRelationIsTargetRelation(EState *estate, Index scanrelid)
return bms_is_member(scanrelid, estate->es_plannedstmt->resultRelationRelids);
}
/*
* Return true if the scan node's relation is not modified by the query.
*
* This is not perfectly accurate. INSERT ... SELECT from the same table does
* not add the scan relation to resultRelationRelids, so it will be reported
* as read-only even though the query modifies it.
*
* Conversely, when any relation in the query has a modifying row mark, all
* other relations get a ROW_MARK_REFERENCE, causing them to be reported as
* not read-only even though they may be.
*/
bool
ScanRelIsReadOnly(ScanState *ss)
{
Index scanrelid = ((Scan *) ss->ps.plan)->scanrelid;
PlannedStmt *pstmt = ss->ps.state->es_plannedstmt;
return !bms_is_member(scanrelid, pstmt->resultRelationRelids) &&
!bms_is_member(scanrelid, pstmt->rowMarkRelids);
}
/* ----------------------------------------------------------------
* ExecOpenScanRelation
*

3
src/backend/executor/nodeBitmapHeapscan.c
View file

@ -149,7 +149,8 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
node->ss.ps.state->es_snapshot,
0,
NULL,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
}
node->ss.ss_currentScanDesc->st.rs_tbmiterator = tbmiterator;

9
src/backend/executor/nodeIndexonlyscan.c
View file

@ -96,7 +96,8 @@ IndexOnlyNext(IndexOnlyScanState *node)
node->ioss_Instrument,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->ioss_ScanDesc = scandesc;
@ -796,7 +797,8 @@ ExecIndexOnlyScanInitializeDSM(IndexOnlyScanState *node,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys,
piscan,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->ioss_ScanDesc->xs_want_itup = true;
node->ioss_VMBuffer = InvalidBuffer;
@ -863,7 +865,8 @@ ExecIndexOnlyScanInitializeWorker(IndexOnlyScanState *node,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys,
piscan,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->ioss_ScanDesc->xs_want_itup = true;
/*

12
src/backend/executor/nodeIndexscan.c
View file

@ -114,7 +114,8 @@ IndexNext(IndexScanState *node)
node->iss_Instrument,
node->iss_NumScanKeys,
node->iss_NumOrderByKeys,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->iss_ScanDesc = scandesc;
@ -211,7 +212,8 @@ IndexNextWithReorder(IndexScanState *node)
node->iss_Instrument,
node->iss_NumScanKeys,
node->iss_NumOrderByKeys,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->iss_ScanDesc = scandesc;
@ -1733,7 +1735,8 @@ ExecIndexScanInitializeDSM(IndexScanState *node,
node->iss_NumScanKeys,
node->iss_NumOrderByKeys,
piscan,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
/*
* If no run-time keys to calculate or they are ready, go ahead and pass
@ -1798,7 +1801,8 @@ ExecIndexScanInitializeWorker(IndexScanState *node,
node->iss_NumScanKeys,
node->iss_NumOrderByKeys,
piscan,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
/*
* If no run-time keys to calculate or they are ready, go ahead and pass

3
src/backend/executor/nodeSamplescan.c
View file

@ -299,7 +299,8 @@ tablesample_init(SampleScanState *scanstate)
scanstate->use_bulkread,
allow_sync,
scanstate->use_pagemode,
SO_NONE);
ScanRelIsReadOnly(&scanstate->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
}
else
{

10
src/backend/executor/nodeSeqscan.c
View file

@ -72,7 +72,8 @@ SeqNext(SeqScanState *node)
scandesc = table_beginscan(node->ss.ss_currentRelation,
estate->es_snapshot,
0, NULL,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->ss.ss_currentScanDesc = scandesc;
}
@ -375,9 +376,11 @@ ExecSeqScanInitializeDSM(SeqScanState *node,
pscan,
estate->es_snapshot);
shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
node->ss.ss_currentScanDesc =
table_beginscan_parallel(node->ss.ss_currentRelation, pscan,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
}
/* ----------------------------------------------------------------
@ -411,5 +414,6 @@ ExecSeqScanInitializeWorker(SeqScanState *node,
pscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
node->ss.ss_currentScanDesc =
table_beginscan_parallel(node->ss.ss_currentRelation, pscan,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
}

11
src/backend/executor/nodeTidrangescan.c
View file

@ -246,7 +246,8 @@ TidRangeNext(TidRangeScanState *node)
estate->es_snapshot,
&node->trss_mintid,
&node->trss_maxtid,
SO_NONE);
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
node->ss.ss_currentScanDesc = scandesc;
}
else
@ -461,7 +462,9 @@ ExecTidRangeScanInitializeDSM(TidRangeScanState *node, ParallelContext *pcxt)
shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
node->ss.ss_currentScanDesc =
table_beginscan_parallel_tidrange(node->ss.ss_currentRelation,
pscan, SO_NONE);
pscan,
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
}
/* ----------------------------------------------------------------
@ -495,5 +498,7 @@ ExecTidRangeScanInitializeWorker(TidRangeScanState *node,
pscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
node->ss.ss_currentScanDesc =
table_beginscan_parallel_tidrange(node->ss.ss_currentRelation,
pscan, SO_NONE);
pscan,
ScanRelIsReadOnly(&node->ss) ?
SO_HINT_REL_READ_ONLY : SO_NONE);
}

3
src/include/access/tableam.h
View file

@ -65,6 +65,9 @@ typedef enum ScanOptions
/* unregister snapshot at scan end? */
SO_TEMP_SNAPSHOT = 1 << 9,
/* set if the query doesn't modify the relation */
SO_HINT_REL_READ_ONLY = 1 << 10,
} ScanOptions;
/*

2
src/include/executor/executor.h
View file

@ -690,6 +690,8 @@ extern void ExecCreateScanSlotFromOuterPlan(EState *estate,
extern bool ExecRelationIsTargetRelation(EState *estate, Index scanrelid);
extern bool ScanRelIsReadOnly(ScanState *ss);
extern Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags);
extern void ExecInitRangeTable(EState *estate, List *rangeTable, List *permInfos,