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Fix parallel index and index-only scans to fall back to serial.

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Parallel executor nodes can't assume that parallel execution will
happen in every case where the plan calls for it, because it might
not work out that way.  However, parallel index scan and parallel
index-only scan failed to do the right thing here.  Repair.

Amit Kapila, per a report from me.

Discussion: http://postgr.es/m/CAA4eK1Kq5qb_u2AOoda5XBB91vVWz90w=LgtRLgsssriS8pVTw@mail.gmail.com
This commit is contained in:
Robert Haas
2017-03-08 08:15:24 -05:00
parent 98e6e89040
commit 09529a70bb
2 changed files with 96 additions and 66 deletions
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72
src/backend/executor/nodeIndexonlyscan.c
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@@ -78,6 +78,38 @@ IndexOnlyNext(IndexOnlyScanState *node)
econtext = node->ss.ps.ps_ExprContext;
slot = node->ss.ss_ScanTupleSlot;
if (scandesc == NULL)
{
/*
* We reach here if the index only scan is not parallel, or if we're
* executing a index only scan that was intended to be parallel
* serially.
*/
scandesc = index_beginscan(node->ss.ss_currentRelation,
node->ioss_RelationDesc,
estate->es_snapshot,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys);
node->ioss_ScanDesc = scandesc;
/* Set it up for index-only scan */
node->ioss_ScanDesc->xs_want_itup = true;
node->ioss_VMBuffer = InvalidBuffer;
/*
* If no run-time keys to calculate or they are ready, go ahead and
* pass the scankeys to the index AM.
*/
if (node->ioss_NumRuntimeKeys == 0 || node->ioss_RuntimeKeysReady)
index_rescan(scandesc,
node->ioss_ScanKeys,
node->ioss_NumScanKeys,
node->ioss_OrderByKeys,
node->ioss_NumOrderByKeys);
}
/*
* OK, now that we have what we need, fetch the next tuple.
*/
@@ -571,34 +603,6 @@ ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
indexstate->ioss_RuntimeContext = NULL;
}
/*
* Initialize scan descriptor.
*/
if (!node->scan.plan.parallel_aware)
{
indexstate->ioss_ScanDesc = index_beginscan(currentRelation,
indexstate->ioss_RelationDesc,
estate->es_snapshot,
indexstate->ioss_NumScanKeys,
indexstate->ioss_NumOrderByKeys);
/* Set it up for index-only scan */
indexstate->ioss_ScanDesc->xs_want_itup = true;
indexstate->ioss_VMBuffer = InvalidBuffer;
/*
* If no run-time keys to calculate, go ahead and pass the scankeys to
* the index AM.
*/
if (indexstate->ioss_NumRuntimeKeys == 0)
index_rescan(indexstate->ioss_ScanDesc,
indexstate->ioss_ScanKeys,
indexstate->ioss_NumScanKeys,
indexstate->ioss_OrderByKeys,
indexstate->ioss_NumOrderByKeys);
}
/*
* all done.
*/
@@ -657,10 +661,10 @@ ExecIndexOnlyScanInitializeDSM(IndexOnlyScanState *node,
node->ioss_VMBuffer = InvalidBuffer;
/*
* If no run-time keys to calculate, go ahead and pass the scankeys to
* the index AM.
* If no run-time keys to calculate or they are ready, go ahead and pass
* the scankeys to the index AM.
*/
if (node->ioss_NumRuntimeKeys == 0)
if (node->ioss_NumRuntimeKeys == 0 || node->ioss_RuntimeKeysReady)
index_rescan(node->ioss_ScanDesc,
node->ioss_ScanKeys, node->ioss_NumScanKeys,
node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
@@ -687,10 +691,10 @@ ExecIndexOnlyScanInitializeWorker(IndexOnlyScanState *node, shm_toc *toc)
node->ioss_ScanDesc->xs_want_itup = true;
/*
* If no run-time keys to calculate, go ahead and pass the scankeys to the
* index AM.
* If no run-time keys to calculate or they are ready, go ahead and pass
* the scankeys to the index AM.
*/
if (node->ioss_NumRuntimeKeys == 0)
if (node->ioss_NumRuntimeKeys == 0 || node->ioss_RuntimeKeysReady)
index_rescan(node->ioss_ScanDesc,
node->ioss_ScanKeys, node->ioss_NumScanKeys,
node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);