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postgres/src/backend/executor/nodeIndexonlyscan.c
Peter Geoghegan 5bf748b86b Enhance nbtree ScalarArrayOp execution. 
Commit 9e8da0f7 taught nbtree to handle ScalarArrayOpExpr quals
natively.  This works by pushing down the full context (the array keys)
to the nbtree index AM, enabling it to execute multiple primitive index
scans that the planner treats as one continuous index scan/index path.
This earlier enhancement enabled nbtree ScalarArrayOp index-only scans.
It also allowed scans with ScalarArrayOp quals to return ordered results
(with some notable restrictions, described further down).

Take this general approach a lot further: teach nbtree SAOP index scans
to decide how to execute ScalarArrayOp scans (when and where to start
the next primitive index scan) based on physical index characteristics.
This can be far more efficient.  All SAOP scans will now reliably avoid
duplicative leaf page accesses (just like any other nbtree index scan).
SAOP scans whose array keys are naturally clustered together now require
far fewer index descents, since we'll reliably avoid starting a new
primitive scan just to get to a later offset from the same leaf page.

The scan's arrays now advance using binary searches for the array
element that best matches the next tuple's attribute value.  Required
scan key arrays (i.e. arrays from scan keys that can terminate the scan)
ratchet forward in lockstep with the index scan.  Non-required arrays
(i.e. arrays from scan keys that can only exclude non-matching tuples)
"advance" without the process ever rolling over to a higher-order array.

Naturally, only required SAOP scan keys trigger skipping over leaf pages
(non-required arrays cannot safely end or start primitive index scans).
Consequently, even index scans of a composite index with a high-order
inequality scan key (which we'll mark required) and a low-order SAOP
scan key (which we won't mark required) now avoid repeating leaf page
accesses -- that benefit isn't limited to simpler equality-only cases.
In general, all nbtree index scans now output tuples as if they were one
continuous index scan -- even scans that mix a high-order inequality
with lower-order SAOP equalities reliably output tuples in index order.
This allows us to remove a couple of special cases that were applied
when building index paths with SAOP clauses during planning.

Bugfix commit 807a40c5 taught the planner to avoid generating unsafe
path keys: path keys on a multicolumn index path, with a SAOP clause on
any attribute beyond the first/most significant attribute.  These cases
are now all safe, so we go back to generating path keys without regard
for the presence of SAOP clauses (just like with any other clause type).
Affected queries can now exploit scan output order in all the usual ways
(e.g., certain "ORDER BY ... LIMIT n" queries can now terminate early).

Also undo changes from follow-up bugfix commit a4523c5a, which taught
the planner to produce alternative index paths, with path keys, but
without low-order SAOP index quals (filter quals were used instead).
We'll no longer generate these alternative paths, since they can no
longer offer any meaningful advantages over standard index qual paths.
Affected queries thereby avoid all of the disadvantages that come from
using filter quals within index scan nodes.  They can avoid extra heap
page accesses from using filter quals to exclude non-matching tuples
(index quals will never have that problem).  They can also skip over
irrelevant sections of the index in more cases (though only when nbtree
determines that starting another primitive scan actually makes sense).

There is a theoretical risk that removing restrictions on SAOP index
paths from the planner will break compatibility with amcanorder-based
index AMs maintained as extensions.  Such an index AM could have the
same limitations around ordered SAOP scans as nbtree had up until now.
Adding a pro forma incompatibility item about the issue to the Postgres
17 release notes seems like a good idea.

Author: Peter Geoghegan <pg@bowt.ie>
Author: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-By: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-By: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/CAH2-Wz=ksvN_sjcnD1+Bt-WtifRA5ok48aDYnq3pkKhxgMQpcw@mail.gmail.com
2024-04-06 11:47:10 -04:00

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/*-------------------------------------------------------------------------
*
* nodeIndexonlyscan.c
* Routines to support index-only scans
*
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeIndexonlyscan.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* ExecIndexOnlyScan scans an index
* IndexOnlyNext retrieve next tuple
* ExecInitIndexOnlyScan creates and initializes state info.
* ExecReScanIndexOnlyScan rescans the indexed relation.
* ExecEndIndexOnlyScan releases all storage.
* ExecIndexOnlyMarkPos marks scan position.
* ExecIndexOnlyRestrPos restores scan position.
* ExecIndexOnlyScanEstimate estimates DSM space needed for
* parallel index-only scan
* ExecIndexOnlyScanInitializeDSM initialize DSM for parallel
* index-only scan
* ExecIndexOnlyScanReInitializeDSM reinitialize DSM for fresh scan
* ExecIndexOnlyScanInitializeWorker attach to DSM info in parallel worker
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/relscan.h"
#include "access/tableam.h"
#include "access/tupdesc.h"
#include "access/visibilitymap.h"
#include "executor/executor.h"
#include "executor/nodeIndexonlyscan.h"
#include "executor/nodeIndexscan.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/predicate.h"
#include "utils/rel.h"
static TupleTableSlot *IndexOnlyNext(IndexOnlyScanState *node);
static void StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup,
TupleDesc itupdesc);
/* ----------------------------------------------------------------
* IndexOnlyNext
*
* Retrieve a tuple from the IndexOnlyScan node's index.
* ----------------------------------------------------------------
*/
static TupleTableSlot *
IndexOnlyNext(IndexOnlyScanState *node)
{
EState *estate;
ExprContext *econtext;
ScanDirection direction;
IndexScanDesc scandesc;
TupleTableSlot *slot;
ItemPointer tid;
/*
* extract necessary information from index scan node
*/
estate = node->ss.ps.state;
/*
* Determine which direction to scan the index in based on the plan's scan
* direction and the current direction of execution.
*/
direction = ScanDirectionCombine(estate->es_direction,
((IndexOnlyScan *) node->ss.ps.plan)->indexorderdir);
scandesc = node->ioss_ScanDesc;
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
* serially executing an index only scan that was planned to be
* parallel.
*/
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.
*/
while ((tid = index_getnext_tid(scandesc, direction)) != NULL)
{
bool tuple_from_heap = false;
CHECK_FOR_INTERRUPTS();
/*
* We can skip the heap fetch if the TID references a heap page on
* which all tuples are known visible to everybody. In any case,
* we'll use the index tuple not the heap tuple as the data source.
*
* Note on Memory Ordering Effects: visibilitymap_get_status does not
* lock the visibility map buffer, and therefore the result we read
* here could be slightly stale. However, it can't be stale enough to
* matter.
*
* We need to detect clearing a VM bit due to an insert right away,
* because the tuple is present in the index page but not visible. The
* reading of the TID by this scan (using a shared lock on the index
* buffer) is serialized with the insert of the TID into the index
* (using an exclusive lock on the index buffer). Because the VM bit
* is cleared before updating the index, and locking/unlocking of the
* index page acts as a full memory barrier, we are sure to see the
* cleared bit if we see a recently-inserted TID.
*
* Deletes do not update the index page (only VACUUM will clear out
* the TID), so the clearing of the VM bit by a delete is not
* serialized with this test below, and we may see a value that is
* significantly stale. However, we don't care about the delete right
* away, because the tuple is still visible until the deleting
* transaction commits or the statement ends (if it's our
* transaction). In either case, the lock on the VM buffer will have
* been released (acting as a write barrier) after clearing the bit.
* And for us to have a snapshot that includes the deleting
* transaction (making the tuple invisible), we must have acquired
* ProcArrayLock after that time, acting as a read barrier.
*
* It's worth going through this complexity to avoid needing to lock
* the VM buffer, which could cause significant contention.
*/
if (!VM_ALL_VISIBLE(scandesc->heapRelation,
ItemPointerGetBlockNumber(tid),
&node->ioss_VMBuffer))
{
/*
* Rats, we have to visit the heap to check visibility.
*/
InstrCountTuples2(node, 1);
if (!index_fetch_heap(scandesc, node->ioss_TableSlot))
continue; /* no visible tuple, try next index entry */
ExecClearTuple(node->ioss_TableSlot);
/*
* Only MVCC snapshots are supported here, so there should be no
* need to keep following the HOT chain once a visible entry has
* been found. If we did want to allow that, we'd need to keep
* more state to remember not to call index_getnext_tid next time.
*/
if (scandesc->xs_heap_continue)
elog(ERROR, "non-MVCC snapshots are not supported in index-only scans");
/*
* Note: at this point we are holding a pin on the heap page, as
* recorded in scandesc->xs_cbuf. We could release that pin now,
* but it's not clear whether it's a win to do so. The next index
* entry might require a visit to the same heap page.
*/
tuple_from_heap = true;
}
/*
* Fill the scan tuple slot with data from the index. This might be
* provided in either HeapTuple or IndexTuple format. Conceivably an
* index AM might fill both fields, in which case we prefer the heap
* format, since it's probably a bit cheaper to fill a slot from.
*/
if (scandesc->xs_hitup)
{
/*
* We don't take the trouble to verify that the provided tuple has
* exactly the slot's format, but it seems worth doing a quick
* check on the number of fields.
*/
Assert(slot->tts_tupleDescriptor->natts ==
scandesc->xs_hitupdesc->natts);
ExecForceStoreHeapTuple(scandesc->xs_hitup, slot, false);
}
else if (scandesc->xs_itup)
StoreIndexTuple(slot, scandesc->xs_itup, scandesc->xs_itupdesc);
else
elog(ERROR, "no data returned for index-only scan");
/*
* If the index was lossy, we have to recheck the index quals.
*/
if (scandesc->xs_recheck)
{
econtext->ecxt_scantuple = slot;
if (!ExecQualAndReset(node->recheckqual, econtext))
{
/* Fails recheck, so drop it and loop back for another */
InstrCountFiltered2(node, 1);
continue;
}
}
/*
* We don't currently support rechecking ORDER BY distances. (In
* principle, if the index can support retrieval of the originally
* indexed value, it should be able to produce an exact distance
* calculation too. So it's not clear that adding code here for
* recheck/re-sort would be worth the trouble. But we should at least
* throw an error if someone tries it.)
*/
if (scandesc->numberOfOrderBys > 0 && scandesc->xs_recheckorderby)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("lossy distance functions are not supported in index-only scans")));
/*
* If we didn't access the heap, then we'll need to take a predicate
* lock explicitly, as if we had. For now we do that at page level.
*/
if (!tuple_from_heap)
PredicateLockPage(scandesc->heapRelation,
ItemPointerGetBlockNumber(tid),
estate->es_snapshot);
return slot;
}
/*
* if we get here it means the index scan failed so we are at the end of
* the scan..
*/
return ExecClearTuple(slot);
}
/*
* StoreIndexTuple
* Fill the slot with data from the index tuple.
*
* At some point this might be generally-useful functionality, but
* right now we don't need it elsewhere.
*/
static void
StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup, TupleDesc itupdesc)
{
/*
* Note: we must use the tupdesc supplied by the AM in index_deform_tuple,
* not the slot's tupdesc, in case the latter has different datatypes
* (this happens for btree name_ops in particular). They'd better have
* the same number of columns though, as well as being datatype-compatible
* which is something we can't so easily check.
*/
Assert(slot->tts_tupleDescriptor->natts == itupdesc->natts);
ExecClearTuple(slot);
index_deform_tuple(itup, itupdesc, slot->tts_values, slot->tts_isnull);
ExecStoreVirtualTuple(slot);
}
/*
* IndexOnlyRecheck -- access method routine to recheck a tuple in EvalPlanQual
*
* This can't really happen, since an index can't supply CTID which would
* be necessary data for any potential EvalPlanQual target relation. If it
* did happen, the EPQ code would pass us the wrong data, namely a heap
* tuple not an index tuple. So throw an error.
*/
static bool
IndexOnlyRecheck(IndexOnlyScanState *node, TupleTableSlot *slot)
{
elog(ERROR, "EvalPlanQual recheck is not supported in index-only scans");
return false; /* keep compiler quiet */
}
/* ----------------------------------------------------------------
* ExecIndexOnlyScan(node)
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ExecIndexOnlyScan(PlanState *pstate)
{
IndexOnlyScanState *node = castNode(IndexOnlyScanState, pstate);
/*
* If we have runtime keys and they've not already been set up, do it now.
*/
if (node->ioss_NumRuntimeKeys != 0 && !node->ioss_RuntimeKeysReady)
ExecReScan((PlanState *) node);
return ExecScan(&node->ss,
(ExecScanAccessMtd) IndexOnlyNext,
(ExecScanRecheckMtd) IndexOnlyRecheck);
}
/* ----------------------------------------------------------------
* ExecReScanIndexOnlyScan(node)
*
* Recalculates the values of any scan keys whose value depends on
* information known at runtime, then rescans the indexed relation.
*
* Updating the scan key was formerly done separately in
* ExecUpdateIndexScanKeys. Integrating it into ReScan makes
* rescans of indices and relations/general streams more uniform.
* ----------------------------------------------------------------
*/
void
ExecReScanIndexOnlyScan(IndexOnlyScanState *node)
{
/*
* If we are doing runtime key calculations (ie, any of the index key
* values weren't simple Consts), compute the new key values. But first,
* reset the context so we don't leak memory as each outer tuple is
* scanned. Note this assumes that we will recalculate *all* runtime keys
* on each call.
*/
if (node->ioss_NumRuntimeKeys != 0)
{
ExprContext *econtext = node->ioss_RuntimeContext;
ResetExprContext(econtext);
ExecIndexEvalRuntimeKeys(econtext,
node->ioss_RuntimeKeys,
node->ioss_NumRuntimeKeys);
}
node->ioss_RuntimeKeysReady = true;
/* reset index scan */
if (node->ioss_ScanDesc)
index_rescan(node->ioss_ScanDesc,
node->ioss_ScanKeys, node->ioss_NumScanKeys,
node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
ExecScanReScan(&node->ss);
}
/* ----------------------------------------------------------------
* ExecEndIndexOnlyScan
* ----------------------------------------------------------------
*/
void
ExecEndIndexOnlyScan(IndexOnlyScanState *node)
{
Relation indexRelationDesc;
IndexScanDesc indexScanDesc;
/*
* extract information from the node
*/
indexRelationDesc = node->ioss_RelationDesc;
indexScanDesc = node->ioss_ScanDesc;
/* Release VM buffer pin, if any. */
if (node->ioss_VMBuffer != InvalidBuffer)
{
ReleaseBuffer(node->ioss_VMBuffer);
node->ioss_VMBuffer = InvalidBuffer;
}
/*
* close the index relation (no-op if we didn't open it)
*/
if (indexScanDesc)
index_endscan(indexScanDesc);
if (indexRelationDesc)
index_close(indexRelationDesc, NoLock);
}
/* ----------------------------------------------------------------
* ExecIndexOnlyMarkPos
*
* Note: we assume that no caller attempts to set a mark before having read
* at least one tuple. Otherwise, ioss_ScanDesc might still be NULL.
* ----------------------------------------------------------------
*/
void
ExecIndexOnlyMarkPos(IndexOnlyScanState *node)
{
EState *estate = node->ss.ps.state;
EPQState *epqstate = estate->es_epq_active;
if (epqstate != NULL)
{
/*
* We are inside an EvalPlanQual recheck. If a test tuple exists for
* this relation, then we shouldn't access the index at all. We would
* instead need to save, and later restore, the state of the
* relsubs_done flag, so that re-fetching the test tuple is possible.
* However, given the assumption that no caller sets a mark at the
* start of the scan, we can only get here with relsubs_done[i]
* already set, and so no state need be saved.
*/
Index scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
Assert(scanrelid > 0);
if (epqstate->relsubs_slot[scanrelid - 1] != NULL ||
epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
{
/* Verify the claim above */
if (!epqstate->relsubs_done[scanrelid - 1])
elog(ERROR, "unexpected ExecIndexOnlyMarkPos call in EPQ recheck");
return;
}
}
index_markpos(node->ioss_ScanDesc);
}
/* ----------------------------------------------------------------
* ExecIndexOnlyRestrPos
* ----------------------------------------------------------------
*/
void
ExecIndexOnlyRestrPos(IndexOnlyScanState *node)
{
EState *estate = node->ss.ps.state;
EPQState *epqstate = estate->es_epq_active;
if (estate->es_epq_active != NULL)
{
/* See comments in ExecIndexMarkPos */
Index scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
Assert(scanrelid > 0);
if (epqstate->relsubs_slot[scanrelid - 1] != NULL ||
epqstate->relsubs_rowmark[scanrelid - 1] != NULL)
{
/* Verify the claim above */
if (!epqstate->relsubs_done[scanrelid - 1])
elog(ERROR, "unexpected ExecIndexOnlyRestrPos call in EPQ recheck");
return;
}
}
index_restrpos(node->ioss_ScanDesc);
}
/* ----------------------------------------------------------------
* ExecInitIndexOnlyScan
*
* Initializes the index scan's state information, creates
* scan keys, and opens the base and index relations.
*
* Note: index scans have 2 sets of state information because
* we have to keep track of the base relation and the
* index relation.
* ----------------------------------------------------------------
*/
IndexOnlyScanState *
ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
{
IndexOnlyScanState *indexstate;
Relation currentRelation;
LOCKMODE lockmode;
TupleDesc tupDesc;
/*
* create state structure
*/
indexstate = makeNode(IndexOnlyScanState);
indexstate->ss.ps.plan = (Plan *) node;
indexstate->ss.ps.state = estate;
indexstate->ss.ps.ExecProcNode = ExecIndexOnlyScan;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &indexstate->ss.ps);
/*
* open the scan relation
*/
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
indexstate->ss.ss_currentRelation = currentRelation;
indexstate->ss.ss_currentScanDesc = NULL; /* no heap scan here */
/*
* Build the scan tuple type using the indextlist generated by the
* planner. We use this, rather than the index's physical tuple
* descriptor, because the latter contains storage column types not the
* types of the original datums. (It's the AM's responsibility to return
* suitable data anyway.)
*/
tupDesc = ExecTypeFromTL(node->indextlist);
ExecInitScanTupleSlot(estate, &indexstate->ss, tupDesc,
&TTSOpsVirtual);
/*
* We need another slot, in a format that's suitable for the table AM, for
* when we need to fetch a tuple from the table for rechecking visibility.
*/
indexstate->ioss_TableSlot =
ExecAllocTableSlot(&estate->es_tupleTable,
RelationGetDescr(currentRelation),
table_slot_callbacks(currentRelation));
/*
* Initialize result type and projection info. The node's targetlist will
* contain Vars with varno = INDEX_VAR, referencing the scan tuple.
*/
ExecInitResultTypeTL(&indexstate->ss.ps);
ExecAssignScanProjectionInfoWithVarno(&indexstate->ss, INDEX_VAR);
/*
* initialize child expressions
*
* Note: we don't initialize all of the indexorderby expression, only the
* sub-parts corresponding to runtime keys (see below).
*/
indexstate->ss.ps.qual =
ExecInitQual(node->scan.plan.qual, (PlanState *) indexstate);
indexstate->recheckqual =
ExecInitQual(node->recheckqual, (PlanState *) indexstate);
/*
* If we are just doing EXPLAIN (ie, aren't going to run the plan), stop
* here. This allows an index-advisor plugin to EXPLAIN a plan containing
* references to nonexistent indexes.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return indexstate;
/* Open the index relation. */
lockmode = exec_rt_fetch(node->scan.scanrelid, estate)->rellockmode;
indexstate->ioss_RelationDesc = index_open(node->indexid, lockmode);
/*
* Initialize index-specific scan state
*/
indexstate->ioss_RuntimeKeysReady = false;
indexstate->ioss_RuntimeKeys = NULL;
indexstate->ioss_NumRuntimeKeys = 0;
/*
* build the index scan keys from the index qualification
*/
ExecIndexBuildScanKeys((PlanState *) indexstate,
indexstate->ioss_RelationDesc,
node->indexqual,
false,
&indexstate->ioss_ScanKeys,
&indexstate->ioss_NumScanKeys,
&indexstate->ioss_RuntimeKeys,
&indexstate->ioss_NumRuntimeKeys,
NULL, /* no ArrayKeys */
NULL);
/*
* any ORDER BY exprs have to be turned into scankeys in the same way
*/
ExecIndexBuildScanKeys((PlanState *) indexstate,
indexstate->ioss_RelationDesc,
node->indexorderby,
true,
&indexstate->ioss_OrderByKeys,
&indexstate->ioss_NumOrderByKeys,
&indexstate->ioss_RuntimeKeys,
&indexstate->ioss_NumRuntimeKeys,
NULL, /* no ArrayKeys */
NULL);
/*
* If we have runtime keys, we need an ExprContext to evaluate them. The
* node's standard context won't do because we want to reset that context
* for every tuple. So, build another context just like the other one...
* -tgl 7/11/00
*/
if (indexstate->ioss_NumRuntimeKeys != 0)
{
ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;
ExecAssignExprContext(estate, &indexstate->ss.ps);
indexstate->ioss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
indexstate->ss.ps.ps_ExprContext = stdecontext;
}
else
{
indexstate->ioss_RuntimeContext = NULL;
}
/*
* all done.
*/
return indexstate;
}
/* ----------------------------------------------------------------
* Parallel Index-only Scan Support
* ----------------------------------------------------------------
*/
/* ----------------------------------------------------------------
* ExecIndexOnlyScanEstimate
*
* Compute the amount of space we'll need in the parallel
* query DSM, and inform pcxt->estimator about our needs.
* ----------------------------------------------------------------
*/
void
ExecIndexOnlyScanEstimate(IndexOnlyScanState *node,
ParallelContext *pcxt)
{
EState *estate = node->ss.ps.state;
node->ioss_PscanLen = index_parallelscan_estimate(node->ioss_RelationDesc,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys,
estate->es_snapshot);
shm_toc_estimate_chunk(&pcxt->estimator, node->ioss_PscanLen);
shm_toc_estimate_keys(&pcxt->estimator, 1);
}
/* ----------------------------------------------------------------
* ExecIndexOnlyScanInitializeDSM
*
* Set up a parallel index-only scan descriptor.
* ----------------------------------------------------------------
*/
void
ExecIndexOnlyScanInitializeDSM(IndexOnlyScanState *node,
ParallelContext *pcxt)
{
EState *estate = node->ss.ps.state;
ParallelIndexScanDesc piscan;
piscan = shm_toc_allocate(pcxt->toc, node->ioss_PscanLen);
index_parallelscan_initialize(node->ss.ss_currentRelation,
node->ioss_RelationDesc,
estate->es_snapshot,
piscan);
shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, piscan);
node->ioss_ScanDesc =
index_beginscan_parallel(node->ss.ss_currentRelation,
node->ioss_RelationDesc,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys,
piscan);
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(node->ioss_ScanDesc,
node->ioss_ScanKeys, node->ioss_NumScanKeys,
node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
}
/* ----------------------------------------------------------------
* ExecIndexOnlyScanReInitializeDSM
*
* Reset shared state before beginning a fresh scan.
* ----------------------------------------------------------------
*/
void
ExecIndexOnlyScanReInitializeDSM(IndexOnlyScanState *node,
ParallelContext *pcxt)
{
index_parallelrescan(node->ioss_ScanDesc);
}
/* ----------------------------------------------------------------
* ExecIndexOnlyScanInitializeWorker
*
* Copy relevant information from TOC into planstate.
* ----------------------------------------------------------------
*/
void
ExecIndexOnlyScanInitializeWorker(IndexOnlyScanState *node,
ParallelWorkerContext *pwcxt)
{
ParallelIndexScanDesc piscan;
piscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
node->ioss_ScanDesc =
index_beginscan_parallel(node->ss.ss_currentRelation,
node->ioss_RelationDesc,
node->ioss_NumScanKeys,
node->ioss_NumOrderByKeys,
piscan);
node->ioss_ScanDesc->xs_want_itup = true;
/*
* 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(node->ioss_ScanDesc,
node->ioss_ScanKeys, node->ioss_NumScanKeys,
node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
}
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