database/postgres
database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-05-15 19:15:29 +03:00
Code
postgres/src/backend/executor/nodeIndexonlyscan.c
Andres Freund c2fe139c20 tableam: Add and use scan APIs. 
Too allow table accesses to be not directly dependent on heap, several
new abstractions are needed. Specifically:

1) Heap scans need to be generalized into table scans. Do this by
   introducing TableScanDesc, which will be the "base class" for
   individual AMs. This contains the AM independent fields from
   HeapScanDesc.

   The previous heap_{beginscan,rescan,endscan} et al. have been
   replaced with a table_ version.

   There's no direct replacement for heap_getnext(), as that returned
   a HeapTuple, which is undesirable for a other AMs. Instead there's
   table_scan_getnextslot().  But note that heap_getnext() lives on,
   it's still used widely to access catalog tables.

   This is achieved by new scan_begin, scan_end, scan_rescan,
   scan_getnextslot callbacks.

2) The portion of parallel scans that's shared between backends need
   to be able to do so without the user doing per-AM work. To achieve
   that new parallelscan_{estimate, initialize, reinitialize}
   callbacks are introduced, which operate on a new
   ParallelTableScanDesc, which again can be subclassed by AMs.

   As it is likely that several AMs are going to be block oriented,
   block oriented callbacks that can be shared between such AMs are
   provided and used by heap. table_block_parallelscan_{estimate,
   intiialize, reinitialize} as callbacks, and
   table_block_parallelscan_{nextpage, init} for use in AMs. These
   operate on a ParallelBlockTableScanDesc.

3) Index scans need to be able to access tables to return a tuple, and
   there needs to be state across individual accesses to the heap to
   store state like buffers. That's now handled by introducing a
   sort-of-scan IndexFetchTable, which again is intended to be
   subclassed by individual AMs (for heap IndexFetchHeap).

   The relevant callbacks for an AM are index_fetch_{end, begin,
   reset} to create the necessary state, and index_fetch_tuple to
   retrieve an indexed tuple.  Note that index_fetch_tuple
   implementations need to be smarter than just blindly fetching the
   tuples for AMs that have optimizations similar to heap's HOT - the
   currently alive tuple in the update chain needs to be fetched if
   appropriate.

   Similar to table_scan_getnextslot(), it's undesirable to continue
   to return HeapTuples. Thus index_fetch_heap (might want to rename
   that later) now accepts a slot as an argument. Core code doesn't
   have a lot of call sites performing index scans without going
   through the systable_* API (in contrast to loads of heap_getnext
   calls and working directly with HeapTuples).

   Index scans now store the result of a search in
   IndexScanDesc->xs_heaptid, rather than xs_ctup->t_self. As the
   target is not generally a HeapTuple anymore that seems cleaner.

To be able to sensible adapt code to use the above, two further
callbacks have been introduced:

a) slot_callbacks returns a TupleTableSlotOps* suitable for creating
   slots capable of holding a tuple of the AMs
   type. table_slot_callbacks() and table_slot_create() are based
   upon that, but have additional logic to deal with views, foreign
   tables, etc.

   While this change could have been done separately, nearly all the
   call sites that needed to be adapted for the rest of this commit
   also would have been needed to be adapted for
   table_slot_callbacks(), making separation not worthwhile.

b) tuple_satisfies_snapshot checks whether the tuple in a slot is
   currently visible according to a snapshot. That's required as a few
   places now don't have a buffer + HeapTuple around, but a
   slot (which in heap's case internally has that information).

Additionally a few infrastructure changes were needed:

I) SysScanDesc, as used by systable_{beginscan, getnext} et al. now
   internally uses a slot to keep track of tuples. While
   systable_getnext() still returns HeapTuples, and will so for the
   foreseeable future, the index API (see 1) above) now only deals with
   slots.

The remainder, and largest part, of this commit is then adjusting all
scans in postgres to use the new APIs.

Author: Andres Freund, Haribabu Kommi, Alvaro Herrera
Discussion:
    https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
    https://postgr.es/m/20160812231527.GA690404@alvherre.pgsql
2019-03-11 12:46:41 -07:00

735 lines
23 KiB
C
Raw Blame History

/*-------------------------------------------------------------------------
*
* nodeIndexonlyscan.c
* Routines to support index-only scans
*
* Portions Copyright (c) 1996-2019, 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/execdebug.h"
#include "executor/nodeIndexonlyscan.h"
#include "executor/nodeIndexscan.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/predicate.h"
#include "utils/memutils.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;
direction = estate->es_direction;
/* flip direction if this is an overall backward scan */
if (ScanDirectionIsBackward(((IndexOnlyScan *) node->ss.ps.plan)->indexorderdir))
{
if (ScanDirectionIsForward(direction))
direction = BackwardScanDirection;
else if (ScanDirectionIsBackward(direction))
direction = ForwardScanDirection;
}
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, slot))
continue; /* no visible tuple, try next index entry */
ExecClearTuple(slot);
/*
* 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);
}
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.
* (Currently, this can never happen, but we should support the case
* for possible future use, eg with GiST indexes.)
*/
if (scandesc->xs_recheck)
{
econtext->ecxt_scantuple = slot;
if (!ExecQualAndReset(node->indexqual, 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")));
/*
* Predicate locks for index-only scans must be acquired at the page
* level when the heap is not accessed, since tuple-level predicate
* locks need the tuple's xmin value. If we had to visit the tuple
* anyway, then we already have the tuple-level lock and can skip the
* page lock.
*/
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;
}
/*
* Free the exprcontext(s) ... now dead code, see ExecFreeExprContext
*/
#ifdef NOT_USED
ExecFreeExprContext(&node->ss.ps);
if (node->ioss_RuntimeContext)
FreeExprContext(node->ioss_RuntimeContext, true);
#endif
/*
* clear out tuple table slots
*/
if (node->ss.ps.ps_ResultTupleSlot)
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
ExecClearTuple(node->ss.ss_ScanTupleSlot);
/*
* 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;
if (estate->es_epqTupleSlot != 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
* es_epqScanDone 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 es_epqScanDone
* already set, and so no state need be saved.
*/
Index scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
Assert(scanrelid > 0);
if (estate->es_epqTupleSlot[scanrelid - 1] != NULL)
{
/* Verify the claim above */
if (!estate->es_epqScanDone[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;
if (estate->es_epqTupleSlot != NULL)
{
/* See comments in ExecIndexOnlyMarkPos */
Index scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
Assert(scanrelid > 0);
if (estate->es_epqTupleSlot[scanrelid - 1])
{
/* Verify the claim above */
if (!estate->es_epqScanDone[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;
bool relistarget;
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,
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->indexqual =
ExecInitQual(node->indexqual, (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.
*
* If the parent table is one of the target relations of the query, then
* InitPlan already opened and write-locked the index, so we can avoid
* taking another lock here. Otherwise we need a normal reader's lock.
*/
relistarget = ExecRelationIsTargetRelation(estate, node->scan.scanrelid);
indexstate->ioss_RelationDesc = index_open(node->indexid,
relistarget ? NoLock : AccessShareLock);
/*
* 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,
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);
}
View Git Blame Copy Permalink