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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
1111 lines
30 KiB
C
1111 lines
30 KiB
C
/*-------------------------------------------------------------------------
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*
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* nodeBitmapHeapscan.c
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* Routines to support bitmapped scans of relations
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*
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* NOTE: it is critical that this plan type only be used with MVCC-compliant
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* snapshots (ie, regular snapshots, not SnapshotAny or one of the other
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* special snapshots). The reason is that since index and heap scans are
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* decoupled, there can be no assurance that the index tuple prompting a
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* visit to a particular heap TID still exists when the visit is made.
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* Therefore the tuple might not exist anymore either (which is OK because
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* heap_fetch will cope) --- but worse, the tuple slot could have been
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* re-used for a newer tuple. With an MVCC snapshot the newer tuple is
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* certain to fail the time qual and so it will not be mistakenly returned,
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* but with anything else we might return a tuple that doesn't meet the
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* required index qual conditions.
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*
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*
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* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/executor/nodeBitmapHeapscan.c
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* INTERFACE ROUTINES
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* ExecBitmapHeapScan scans a relation using bitmap info
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* ExecBitmapHeapNext workhorse for above
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* ExecInitBitmapHeapScan creates and initializes state info.
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* ExecReScanBitmapHeapScan prepares to rescan the plan.
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* ExecEndBitmapHeapScan releases all storage.
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*/
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#include "postgres.h"
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#include <math.h>
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#include "access/heapam.h"
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#include "access/relscan.h"
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#include "access/tableam.h"
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#include "access/transam.h"
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#include "access/visibilitymap.h"
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#include "executor/execdebug.h"
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#include "executor/nodeBitmapHeapscan.h"
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#include "miscadmin.h"
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#include "pgstat.h"
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#include "storage/bufmgr.h"
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#include "storage/predicate.h"
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#include "utils/memutils.h"
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#include "utils/rel.h"
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#include "utils/spccache.h"
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#include "utils/snapmgr.h"
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static TupleTableSlot *BitmapHeapNext(BitmapHeapScanState *node);
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static void bitgetpage(HeapScanDesc scan, TBMIterateResult *tbmres);
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static inline void BitmapDoneInitializingSharedState(
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ParallelBitmapHeapState *pstate);
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static inline void BitmapAdjustPrefetchIterator(BitmapHeapScanState *node,
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TBMIterateResult *tbmres);
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static inline void BitmapAdjustPrefetchTarget(BitmapHeapScanState *node);
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static inline void BitmapPrefetch(BitmapHeapScanState *node,
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TableScanDesc scan);
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static bool BitmapShouldInitializeSharedState(
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ParallelBitmapHeapState *pstate);
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/* ----------------------------------------------------------------
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* BitmapHeapNext
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*
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* Retrieve next tuple from the BitmapHeapScan node's currentRelation
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* ----------------------------------------------------------------
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*/
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static TupleTableSlot *
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BitmapHeapNext(BitmapHeapScanState *node)
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{
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ExprContext *econtext;
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TableScanDesc scan;
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HeapScanDesc hscan;
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TIDBitmap *tbm;
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TBMIterator *tbmiterator = NULL;
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TBMSharedIterator *shared_tbmiterator = NULL;
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TBMIterateResult *tbmres;
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OffsetNumber targoffset;
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TupleTableSlot *slot;
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ParallelBitmapHeapState *pstate = node->pstate;
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dsa_area *dsa = node->ss.ps.state->es_query_dsa;
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/*
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* extract necessary information from index scan node
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*/
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econtext = node->ss.ps.ps_ExprContext;
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slot = node->ss.ss_ScanTupleSlot;
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scan = node->ss.ss_currentScanDesc;
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hscan = (HeapScanDesc) scan;
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tbm = node->tbm;
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if (pstate == NULL)
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tbmiterator = node->tbmiterator;
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else
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shared_tbmiterator = node->shared_tbmiterator;
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tbmres = node->tbmres;
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/*
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* If we haven't yet performed the underlying index scan, do it, and begin
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* the iteration over the bitmap.
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*
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* For prefetching, we use *two* iterators, one for the pages we are
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* actually scanning and another that runs ahead of the first for
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* prefetching. node->prefetch_pages tracks exactly how many pages ahead
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* the prefetch iterator is. Also, node->prefetch_target tracks the
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* desired prefetch distance, which starts small and increases up to the
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* node->prefetch_maximum. This is to avoid doing a lot of prefetching in
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* a scan that stops after a few tuples because of a LIMIT.
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*/
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if (!node->initialized)
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{
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if (!pstate)
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{
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tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node));
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if (!tbm || !IsA(tbm, TIDBitmap))
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elog(ERROR, "unrecognized result from subplan");
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node->tbm = tbm;
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node->tbmiterator = tbmiterator = tbm_begin_iterate(tbm);
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node->tbmres = tbmres = NULL;
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#ifdef USE_PREFETCH
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if (node->prefetch_maximum > 0)
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{
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node->prefetch_iterator = tbm_begin_iterate(tbm);
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node->prefetch_pages = 0;
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node->prefetch_target = -1;
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}
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#endif /* USE_PREFETCH */
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}
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else
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{
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/*
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* The leader will immediately come out of the function, but
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* others will be blocked until leader populates the TBM and wakes
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* them up.
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*/
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if (BitmapShouldInitializeSharedState(pstate))
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{
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tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node));
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if (!tbm || !IsA(tbm, TIDBitmap))
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elog(ERROR, "unrecognized result from subplan");
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node->tbm = tbm;
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/*
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* Prepare to iterate over the TBM. This will return the
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* dsa_pointer of the iterator state which will be used by
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* multiple processes to iterate jointly.
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*/
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pstate->tbmiterator = tbm_prepare_shared_iterate(tbm);
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#ifdef USE_PREFETCH
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if (node->prefetch_maximum > 0)
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{
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pstate->prefetch_iterator =
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tbm_prepare_shared_iterate(tbm);
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/*
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* We don't need the mutex here as we haven't yet woke up
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* others.
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*/
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pstate->prefetch_pages = 0;
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pstate->prefetch_target = -1;
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}
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#endif
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/* We have initialized the shared state so wake up others. */
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BitmapDoneInitializingSharedState(pstate);
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}
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/* Allocate a private iterator and attach the shared state to it */
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node->shared_tbmiterator = shared_tbmiterator =
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tbm_attach_shared_iterate(dsa, pstate->tbmiterator);
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node->tbmres = tbmres = NULL;
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#ifdef USE_PREFETCH
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if (node->prefetch_maximum > 0)
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{
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node->shared_prefetch_iterator =
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tbm_attach_shared_iterate(dsa, pstate->prefetch_iterator);
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}
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#endif /* USE_PREFETCH */
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}
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node->initialized = true;
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}
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for (;;)
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{
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Page dp;
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ItemId lp;
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CHECK_FOR_INTERRUPTS();
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/*
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* Get next page of results if needed
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*/
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if (tbmres == NULL)
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{
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if (!pstate)
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node->tbmres = tbmres = tbm_iterate(tbmiterator);
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else
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node->tbmres = tbmres = tbm_shared_iterate(shared_tbmiterator);
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if (tbmres == NULL)
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{
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/* no more entries in the bitmap */
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break;
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}
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BitmapAdjustPrefetchIterator(node, tbmres);
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/*
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* Ignore any claimed entries past what we think is the end of the
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* relation. (This is probably not necessary given that we got at
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* least AccessShareLock on the table before performing any of the
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* indexscans, but let's be safe.)
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*/
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if (tbmres->blockno >= hscan->rs_nblocks)
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{
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node->tbmres = tbmres = NULL;
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continue;
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}
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/*
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* We can skip fetching the heap page if we don't need any fields
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* from the heap, and the bitmap entries don't need rechecking,
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* and all tuples on the page are visible to our transaction.
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*/
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node->skip_fetch = (node->can_skip_fetch &&
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!tbmres->recheck &&
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VM_ALL_VISIBLE(node->ss.ss_currentRelation,
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tbmres->blockno,
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&node->vmbuffer));
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if (node->skip_fetch)
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{
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/*
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* The number of tuples on this page is put into
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* scan->rs_ntuples; note we don't fill scan->rs_vistuples.
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*/
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hscan->rs_ntuples = tbmres->ntuples;
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}
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else
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{
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/*
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* Fetch the current heap page and identify candidate tuples.
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*/
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bitgetpage(hscan, tbmres);
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}
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if (tbmres->ntuples >= 0)
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node->exact_pages++;
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else
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node->lossy_pages++;
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/*
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* Set rs_cindex to first slot to examine
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*/
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hscan->rs_cindex = 0;
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/* Adjust the prefetch target */
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BitmapAdjustPrefetchTarget(node);
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}
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else
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{
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/*
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* Continuing in previously obtained page; advance rs_cindex
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*/
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hscan->rs_cindex++;
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#ifdef USE_PREFETCH
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/*
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* Try to prefetch at least a few pages even before we get to the
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* second page if we don't stop reading after the first tuple.
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*/
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if (!pstate)
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{
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if (node->prefetch_target < node->prefetch_maximum)
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node->prefetch_target++;
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}
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else if (pstate->prefetch_target < node->prefetch_maximum)
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{
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/* take spinlock while updating shared state */
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SpinLockAcquire(&pstate->mutex);
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if (pstate->prefetch_target < node->prefetch_maximum)
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pstate->prefetch_target++;
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SpinLockRelease(&pstate->mutex);
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}
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#endif /* USE_PREFETCH */
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}
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/*
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* Out of range? If so, nothing more to look at on this page
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*/
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if (hscan->rs_cindex < 0 || hscan->rs_cindex >= hscan->rs_ntuples)
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{
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node->tbmres = tbmres = NULL;
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continue;
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}
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/*
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* We issue prefetch requests *after* fetching the current page to try
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* to avoid having prefetching interfere with the main I/O. Also, this
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* should happen only when we have determined there is still something
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* to do on the current page, else we may uselessly prefetch the same
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* page we are just about to request for real.
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*/
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BitmapPrefetch(node, scan);
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if (node->skip_fetch)
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{
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/*
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* If we don't have to fetch the tuple, just return nulls.
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*/
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ExecStoreAllNullTuple(slot);
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}
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else
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{
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/*
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* Okay to fetch the tuple.
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*/
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targoffset = hscan->rs_vistuples[hscan->rs_cindex];
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dp = (Page) BufferGetPage(hscan->rs_cbuf);
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lp = PageGetItemId(dp, targoffset);
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Assert(ItemIdIsNormal(lp));
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hscan->rs_ctup.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
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hscan->rs_ctup.t_len = ItemIdGetLength(lp);
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hscan->rs_ctup.t_tableOid = scan->rs_rd->rd_id;
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ItemPointerSet(&hscan->rs_ctup.t_self, tbmres->blockno, targoffset);
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pgstat_count_heap_fetch(scan->rs_rd);
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/*
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* Set up the result slot to point to this tuple. Note that the
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* slot acquires a pin on the buffer.
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*/
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ExecStoreBufferHeapTuple(&hscan->rs_ctup,
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slot,
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hscan->rs_cbuf);
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/*
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* If we are using lossy info, we have to recheck the qual
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* conditions at every tuple.
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*/
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if (tbmres->recheck)
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{
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econtext->ecxt_scantuple = slot;
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if (!ExecQualAndReset(node->bitmapqualorig, econtext))
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{
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/* Fails recheck, so drop it and loop back for another */
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InstrCountFiltered2(node, 1);
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ExecClearTuple(slot);
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continue;
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}
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}
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}
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/* OK to return this tuple */
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return slot;
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}
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/*
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* if we get here it means we are at the end of the scan..
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*/
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return ExecClearTuple(slot);
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}
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/*
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* bitgetpage - subroutine for BitmapHeapNext()
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*
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* This routine reads and pins the specified page of the relation, then
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* builds an array indicating which tuples on the page are both potentially
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* interesting according to the bitmap, and visible according to the snapshot.
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*/
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static void
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bitgetpage(HeapScanDesc scan, TBMIterateResult *tbmres)
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{
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BlockNumber page = tbmres->blockno;
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Buffer buffer;
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Snapshot snapshot;
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int ntup;
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/*
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* Acquire pin on the target heap page, trading in any pin we held before.
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*/
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Assert(page < scan->rs_nblocks);
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scan->rs_cbuf = ReleaseAndReadBuffer(scan->rs_cbuf,
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scan->rs_base.rs_rd,
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page);
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buffer = scan->rs_cbuf;
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snapshot = scan->rs_base.rs_snapshot;
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ntup = 0;
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/*
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* Prune and repair fragmentation for the whole page, if possible.
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*/
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heap_page_prune_opt(scan->rs_base.rs_rd, buffer);
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/*
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* We must hold share lock on the buffer content while examining tuple
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* visibility. Afterwards, however, the tuples we have found to be
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* visible are guaranteed good as long as we hold the buffer pin.
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*/
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LockBuffer(buffer, BUFFER_LOCK_SHARE);
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/*
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* We need two separate strategies for lossy and non-lossy cases.
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*/
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if (tbmres->ntuples >= 0)
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{
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/*
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* Bitmap is non-lossy, so we just look through the offsets listed in
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* tbmres; but we have to follow any HOT chain starting at each such
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* offset.
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*/
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int curslot;
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for (curslot = 0; curslot < tbmres->ntuples; curslot++)
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{
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OffsetNumber offnum = tbmres->offsets[curslot];
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ItemPointerData tid;
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HeapTupleData heapTuple;
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ItemPointerSet(&tid, page, offnum);
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if (heap_hot_search_buffer(&tid, scan->rs_base.rs_rd, buffer,
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snapshot, &heapTuple, NULL, true))
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scan->rs_vistuples[ntup++] = ItemPointerGetOffsetNumber(&tid);
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}
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}
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else
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{
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/*
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* Bitmap is lossy, so we must examine each item pointer on the page.
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* But we can ignore HOT chains, since we'll check each tuple anyway.
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*/
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Page dp = (Page) BufferGetPage(buffer);
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OffsetNumber maxoff = PageGetMaxOffsetNumber(dp);
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OffsetNumber offnum;
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for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum))
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{
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ItemId lp;
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HeapTupleData loctup;
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bool valid;
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lp = PageGetItemId(dp, offnum);
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if (!ItemIdIsNormal(lp))
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continue;
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loctup.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
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loctup.t_len = ItemIdGetLength(lp);
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loctup.t_tableOid = scan->rs_base.rs_rd->rd_id;
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ItemPointerSet(&loctup.t_self, page, offnum);
|
|
valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer);
|
|
if (valid)
|
|
{
|
|
scan->rs_vistuples[ntup++] = offnum;
|
|
PredicateLockTuple(scan->rs_base.rs_rd, &loctup, snapshot);
|
|
}
|
|
CheckForSerializableConflictOut(valid, scan->rs_base.rs_rd,
|
|
&loctup, buffer, snapshot);
|
|
}
|
|
}
|
|
|
|
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
|
|
|
|
Assert(ntup <= MaxHeapTuplesPerPage);
|
|
scan->rs_ntuples = ntup;
|
|
}
|
|
|
|
/*
|
|
* BitmapDoneInitializingSharedState - Shared state is initialized
|
|
*
|
|
* By this time the leader has already populated the TBM and initialized the
|
|
* shared state so wake up other processes.
|
|
*/
|
|
static inline void
|
|
BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate)
|
|
{
|
|
SpinLockAcquire(&pstate->mutex);
|
|
pstate->state = BM_FINISHED;
|
|
SpinLockRelease(&pstate->mutex);
|
|
ConditionVariableBroadcast(&pstate->cv);
|
|
}
|
|
|
|
/*
|
|
* BitmapAdjustPrefetchIterator - Adjust the prefetch iterator
|
|
*/
|
|
static inline void
|
|
BitmapAdjustPrefetchIterator(BitmapHeapScanState *node,
|
|
TBMIterateResult *tbmres)
|
|
{
|
|
#ifdef USE_PREFETCH
|
|
ParallelBitmapHeapState *pstate = node->pstate;
|
|
|
|
if (pstate == NULL)
|
|
{
|
|
TBMIterator *prefetch_iterator = node->prefetch_iterator;
|
|
|
|
if (node->prefetch_pages > 0)
|
|
{
|
|
/* The main iterator has closed the distance by one page */
|
|
node->prefetch_pages--;
|
|
}
|
|
else if (prefetch_iterator)
|
|
{
|
|
/* Do not let the prefetch iterator get behind the main one */
|
|
TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
|
|
|
|
if (tbmpre == NULL || tbmpre->blockno != tbmres->blockno)
|
|
elog(ERROR, "prefetch and main iterators are out of sync");
|
|
}
|
|
return;
|
|
}
|
|
|
|
if (node->prefetch_maximum > 0)
|
|
{
|
|
TBMSharedIterator *prefetch_iterator = node->shared_prefetch_iterator;
|
|
|
|
SpinLockAcquire(&pstate->mutex);
|
|
if (pstate->prefetch_pages > 0)
|
|
{
|
|
pstate->prefetch_pages--;
|
|
SpinLockRelease(&pstate->mutex);
|
|
}
|
|
else
|
|
{
|
|
/* Release the mutex before iterating */
|
|
SpinLockRelease(&pstate->mutex);
|
|
|
|
/*
|
|
* In case of shared mode, we can not ensure that the current
|
|
* blockno of the main iterator and that of the prefetch iterator
|
|
* are same. It's possible that whatever blockno we are
|
|
* prefetching will be processed by another process. Therefore,
|
|
* we don't validate the blockno here as we do in non-parallel
|
|
* case.
|
|
*/
|
|
if (prefetch_iterator)
|
|
tbm_shared_iterate(prefetch_iterator);
|
|
}
|
|
}
|
|
#endif /* USE_PREFETCH */
|
|
}
|
|
|
|
/*
|
|
* BitmapAdjustPrefetchTarget - Adjust the prefetch target
|
|
*
|
|
* Increase prefetch target if it's not yet at the max. Note that
|
|
* we will increase it to zero after fetching the very first
|
|
* page/tuple, then to one after the second tuple is fetched, then
|
|
* it doubles as later pages are fetched.
|
|
*/
|
|
static inline void
|
|
BitmapAdjustPrefetchTarget(BitmapHeapScanState *node)
|
|
{
|
|
#ifdef USE_PREFETCH
|
|
ParallelBitmapHeapState *pstate = node->pstate;
|
|
|
|
if (pstate == NULL)
|
|
{
|
|
if (node->prefetch_target >= node->prefetch_maximum)
|
|
/* don't increase any further */ ;
|
|
else if (node->prefetch_target >= node->prefetch_maximum / 2)
|
|
node->prefetch_target = node->prefetch_maximum;
|
|
else if (node->prefetch_target > 0)
|
|
node->prefetch_target *= 2;
|
|
else
|
|
node->prefetch_target++;
|
|
return;
|
|
}
|
|
|
|
/* Do an unlocked check first to save spinlock acquisitions. */
|
|
if (pstate->prefetch_target < node->prefetch_maximum)
|
|
{
|
|
SpinLockAcquire(&pstate->mutex);
|
|
if (pstate->prefetch_target >= node->prefetch_maximum)
|
|
/* don't increase any further */ ;
|
|
else if (pstate->prefetch_target >= node->prefetch_maximum / 2)
|
|
pstate->prefetch_target = node->prefetch_maximum;
|
|
else if (pstate->prefetch_target > 0)
|
|
pstate->prefetch_target *= 2;
|
|
else
|
|
pstate->prefetch_target++;
|
|
SpinLockRelease(&pstate->mutex);
|
|
}
|
|
#endif /* USE_PREFETCH */
|
|
}
|
|
|
|
/*
|
|
* BitmapPrefetch - Prefetch, if prefetch_pages are behind prefetch_target
|
|
*/
|
|
static inline void
|
|
BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
|
|
{
|
|
#ifdef USE_PREFETCH
|
|
ParallelBitmapHeapState *pstate = node->pstate;
|
|
|
|
if (pstate == NULL)
|
|
{
|
|
TBMIterator *prefetch_iterator = node->prefetch_iterator;
|
|
|
|
if (prefetch_iterator)
|
|
{
|
|
while (node->prefetch_pages < node->prefetch_target)
|
|
{
|
|
TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
|
|
bool skip_fetch;
|
|
|
|
if (tbmpre == NULL)
|
|
{
|
|
/* No more pages to prefetch */
|
|
tbm_end_iterate(prefetch_iterator);
|
|
node->prefetch_iterator = NULL;
|
|
break;
|
|
}
|
|
node->prefetch_pages++;
|
|
|
|
/*
|
|
* If we expect not to have to actually read this heap page,
|
|
* skip this prefetch call, but continue to run the prefetch
|
|
* logic normally. (Would it be better not to increment
|
|
* prefetch_pages?)
|
|
*
|
|
* This depends on the assumption that the index AM will
|
|
* report the same recheck flag for this future heap page as
|
|
* it did for the current heap page; which is not a certainty
|
|
* but is true in many cases.
|
|
*/
|
|
skip_fetch = (node->can_skip_fetch &&
|
|
(node->tbmres ? !node->tbmres->recheck : false) &&
|
|
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
|
|
tbmpre->blockno,
|
|
&node->pvmbuffer));
|
|
|
|
if (!skip_fetch)
|
|
PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
|
|
}
|
|
}
|
|
|
|
return;
|
|
}
|
|
|
|
if (pstate->prefetch_pages < pstate->prefetch_target)
|
|
{
|
|
TBMSharedIterator *prefetch_iterator = node->shared_prefetch_iterator;
|
|
|
|
if (prefetch_iterator)
|
|
{
|
|
while (1)
|
|
{
|
|
TBMIterateResult *tbmpre;
|
|
bool do_prefetch = false;
|
|
bool skip_fetch;
|
|
|
|
/*
|
|
* Recheck under the mutex. If some other process has already
|
|
* done enough prefetching then we need not to do anything.
|
|
*/
|
|
SpinLockAcquire(&pstate->mutex);
|
|
if (pstate->prefetch_pages < pstate->prefetch_target)
|
|
{
|
|
pstate->prefetch_pages++;
|
|
do_prefetch = true;
|
|
}
|
|
SpinLockRelease(&pstate->mutex);
|
|
|
|
if (!do_prefetch)
|
|
return;
|
|
|
|
tbmpre = tbm_shared_iterate(prefetch_iterator);
|
|
if (tbmpre == NULL)
|
|
{
|
|
/* No more pages to prefetch */
|
|
tbm_end_shared_iterate(prefetch_iterator);
|
|
node->shared_prefetch_iterator = NULL;
|
|
break;
|
|
}
|
|
|
|
/* As above, skip prefetch if we expect not to need page */
|
|
skip_fetch = (node->can_skip_fetch &&
|
|
(node->tbmres ? !node->tbmres->recheck : false) &&
|
|
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
|
|
tbmpre->blockno,
|
|
&node->pvmbuffer));
|
|
|
|
if (!skip_fetch)
|
|
PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
|
|
}
|
|
}
|
|
}
|
|
#endif /* USE_PREFETCH */
|
|
}
|
|
|
|
/*
|
|
* BitmapHeapRecheck -- access method routine to recheck a tuple in EvalPlanQual
|
|
*/
|
|
static bool
|
|
BitmapHeapRecheck(BitmapHeapScanState *node, TupleTableSlot *slot)
|
|
{
|
|
ExprContext *econtext;
|
|
|
|
/*
|
|
* extract necessary information from index scan node
|
|
*/
|
|
econtext = node->ss.ps.ps_ExprContext;
|
|
|
|
/* Does the tuple meet the original qual conditions? */
|
|
econtext->ecxt_scantuple = slot;
|
|
return ExecQualAndReset(node->bitmapqualorig, econtext);
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecBitmapHeapScan(node)
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
static TupleTableSlot *
|
|
ExecBitmapHeapScan(PlanState *pstate)
|
|
{
|
|
BitmapHeapScanState *node = castNode(BitmapHeapScanState, pstate);
|
|
|
|
return ExecScan(&node->ss,
|
|
(ExecScanAccessMtd) BitmapHeapNext,
|
|
(ExecScanRecheckMtd) BitmapHeapRecheck);
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecReScanBitmapHeapScan(node)
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecReScanBitmapHeapScan(BitmapHeapScanState *node)
|
|
{
|
|
PlanState *outerPlan = outerPlanState(node);
|
|
|
|
/* rescan to release any page pin */
|
|
table_rescan(node->ss.ss_currentScanDesc, NULL);
|
|
|
|
/* release bitmaps and buffers if any */
|
|
if (node->tbmiterator)
|
|
tbm_end_iterate(node->tbmiterator);
|
|
if (node->prefetch_iterator)
|
|
tbm_end_iterate(node->prefetch_iterator);
|
|
if (node->shared_tbmiterator)
|
|
tbm_end_shared_iterate(node->shared_tbmiterator);
|
|
if (node->shared_prefetch_iterator)
|
|
tbm_end_shared_iterate(node->shared_prefetch_iterator);
|
|
if (node->tbm)
|
|
tbm_free(node->tbm);
|
|
if (node->vmbuffer != InvalidBuffer)
|
|
ReleaseBuffer(node->vmbuffer);
|
|
if (node->pvmbuffer != InvalidBuffer)
|
|
ReleaseBuffer(node->pvmbuffer);
|
|
node->tbm = NULL;
|
|
node->tbmiterator = NULL;
|
|
node->tbmres = NULL;
|
|
node->prefetch_iterator = NULL;
|
|
node->initialized = false;
|
|
node->shared_tbmiterator = NULL;
|
|
node->shared_prefetch_iterator = NULL;
|
|
node->vmbuffer = InvalidBuffer;
|
|
node->pvmbuffer = InvalidBuffer;
|
|
|
|
ExecScanReScan(&node->ss);
|
|
|
|
/*
|
|
* if chgParam of subnode is not null then plan will be re-scanned by
|
|
* first ExecProcNode.
|
|
*/
|
|
if (outerPlan->chgParam == NULL)
|
|
ExecReScan(outerPlan);
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecEndBitmapHeapScan
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecEndBitmapHeapScan(BitmapHeapScanState *node)
|
|
{
|
|
TableScanDesc scanDesc;
|
|
|
|
/*
|
|
* extract information from the node
|
|
*/
|
|
scanDesc = node->ss.ss_currentScanDesc;
|
|
|
|
/*
|
|
* Free the exprcontext
|
|
*/
|
|
ExecFreeExprContext(&node->ss.ps);
|
|
|
|
/*
|
|
* clear out tuple table slots
|
|
*/
|
|
if (node->ss.ps.ps_ResultTupleSlot)
|
|
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
|
|
ExecClearTuple(node->ss.ss_ScanTupleSlot);
|
|
|
|
/*
|
|
* close down subplans
|
|
*/
|
|
ExecEndNode(outerPlanState(node));
|
|
|
|
/*
|
|
* release bitmaps and buffers if any
|
|
*/
|
|
if (node->tbmiterator)
|
|
tbm_end_iterate(node->tbmiterator);
|
|
if (node->prefetch_iterator)
|
|
tbm_end_iterate(node->prefetch_iterator);
|
|
if (node->tbm)
|
|
tbm_free(node->tbm);
|
|
if (node->shared_tbmiterator)
|
|
tbm_end_shared_iterate(node->shared_tbmiterator);
|
|
if (node->shared_prefetch_iterator)
|
|
tbm_end_shared_iterate(node->shared_prefetch_iterator);
|
|
if (node->vmbuffer != InvalidBuffer)
|
|
ReleaseBuffer(node->vmbuffer);
|
|
if (node->pvmbuffer != InvalidBuffer)
|
|
ReleaseBuffer(node->pvmbuffer);
|
|
|
|
/*
|
|
* close heap scan
|
|
*/
|
|
table_endscan(scanDesc);
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecInitBitmapHeapScan
|
|
*
|
|
* Initializes the scan's state information.
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
BitmapHeapScanState *
|
|
ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
|
|
{
|
|
BitmapHeapScanState *scanstate;
|
|
Relation currentRelation;
|
|
int io_concurrency;
|
|
|
|
/* check for unsupported flags */
|
|
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
|
|
|
|
/*
|
|
* Assert caller didn't ask for an unsafe snapshot --- see comments at
|
|
* head of file.
|
|
*/
|
|
Assert(IsMVCCSnapshot(estate->es_snapshot));
|
|
|
|
/*
|
|
* create state structure
|
|
*/
|
|
scanstate = makeNode(BitmapHeapScanState);
|
|
scanstate->ss.ps.plan = (Plan *) node;
|
|
scanstate->ss.ps.state = estate;
|
|
scanstate->ss.ps.ExecProcNode = ExecBitmapHeapScan;
|
|
|
|
scanstate->tbm = NULL;
|
|
scanstate->tbmiterator = NULL;
|
|
scanstate->tbmres = NULL;
|
|
scanstate->skip_fetch = false;
|
|
scanstate->vmbuffer = InvalidBuffer;
|
|
scanstate->pvmbuffer = InvalidBuffer;
|
|
scanstate->exact_pages = 0;
|
|
scanstate->lossy_pages = 0;
|
|
scanstate->prefetch_iterator = NULL;
|
|
scanstate->prefetch_pages = 0;
|
|
scanstate->prefetch_target = 0;
|
|
/* may be updated below */
|
|
scanstate->prefetch_maximum = target_prefetch_pages;
|
|
scanstate->pscan_len = 0;
|
|
scanstate->initialized = false;
|
|
scanstate->shared_tbmiterator = NULL;
|
|
scanstate->shared_prefetch_iterator = NULL;
|
|
scanstate->pstate = NULL;
|
|
|
|
/*
|
|
* We can potentially skip fetching heap pages if we do not need any
|
|
* columns of the table, either for checking non-indexable quals or for
|
|
* returning data. This test is a bit simplistic, as it checks the
|
|
* stronger condition that there's no qual or return tlist at all. But in
|
|
* most cases it's probably not worth working harder than that.
|
|
*/
|
|
scanstate->can_skip_fetch = (node->scan.plan.qual == NIL &&
|
|
node->scan.plan.targetlist == NIL);
|
|
|
|
/*
|
|
* Miscellaneous initialization
|
|
*
|
|
* create expression context for node
|
|
*/
|
|
ExecAssignExprContext(estate, &scanstate->ss.ps);
|
|
|
|
/*
|
|
* open the scan relation
|
|
*/
|
|
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
|
|
|
|
/*
|
|
* initialize child nodes
|
|
*/
|
|
outerPlanState(scanstate) = ExecInitNode(outerPlan(node), estate, eflags);
|
|
|
|
/*
|
|
* get the scan type from the relation descriptor.
|
|
*/
|
|
ExecInitScanTupleSlot(estate, &scanstate->ss,
|
|
RelationGetDescr(currentRelation),
|
|
table_slot_callbacks(currentRelation));
|
|
|
|
/*
|
|
* Initialize result type and projection.
|
|
*/
|
|
ExecInitResultTypeTL(&scanstate->ss.ps);
|
|
ExecAssignScanProjectionInfo(&scanstate->ss);
|
|
|
|
/*
|
|
* initialize child expressions
|
|
*/
|
|
scanstate->ss.ps.qual =
|
|
ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
|
|
scanstate->bitmapqualorig =
|
|
ExecInitQual(node->bitmapqualorig, (PlanState *) scanstate);
|
|
|
|
/*
|
|
* Determine the maximum for prefetch_target. If the tablespace has a
|
|
* specific IO concurrency set, use that to compute the corresponding
|
|
* maximum value; otherwise, we already initialized to the value computed
|
|
* by the GUC machinery.
|
|
*/
|
|
io_concurrency =
|
|
get_tablespace_io_concurrency(currentRelation->rd_rel->reltablespace);
|
|
if (io_concurrency != effective_io_concurrency)
|
|
{
|
|
double maximum;
|
|
|
|
if (ComputeIoConcurrency(io_concurrency, &maximum))
|
|
scanstate->prefetch_maximum = rint(maximum);
|
|
}
|
|
|
|
scanstate->ss.ss_currentRelation = currentRelation;
|
|
|
|
/*
|
|
* Even though we aren't going to do a conventional seqscan, it is useful
|
|
* to create a HeapScanDesc --- most of the fields in it are usable.
|
|
*/
|
|
scanstate->ss.ss_currentScanDesc = table_beginscan_bm(currentRelation,
|
|
estate->es_snapshot,
|
|
0,
|
|
NULL);
|
|
|
|
/*
|
|
* all done.
|
|
*/
|
|
return scanstate;
|
|
}
|
|
|
|
/*----------------
|
|
* BitmapShouldInitializeSharedState
|
|
*
|
|
* The first process to come here and see the state to the BM_INITIAL
|
|
* will become the leader for the parallel bitmap scan and will be
|
|
* responsible for populating the TIDBitmap. The other processes will
|
|
* be blocked by the condition variable until the leader wakes them up.
|
|
* ---------------
|
|
*/
|
|
static bool
|
|
BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate)
|
|
{
|
|
SharedBitmapState state;
|
|
|
|
while (1)
|
|
{
|
|
SpinLockAcquire(&pstate->mutex);
|
|
state = pstate->state;
|
|
if (pstate->state == BM_INITIAL)
|
|
pstate->state = BM_INPROGRESS;
|
|
SpinLockRelease(&pstate->mutex);
|
|
|
|
/* Exit if bitmap is done, or if we're the leader. */
|
|
if (state != BM_INPROGRESS)
|
|
break;
|
|
|
|
/* Wait for the leader to wake us up. */
|
|
ConditionVariableSleep(&pstate->cv, WAIT_EVENT_PARALLEL_BITMAP_SCAN);
|
|
}
|
|
|
|
ConditionVariableCancelSleep();
|
|
|
|
return (state == BM_INITIAL);
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecBitmapHeapEstimate
|
|
*
|
|
* Compute the amount of space we'll need in the parallel
|
|
* query DSM, and inform pcxt->estimator about our needs.
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecBitmapHeapEstimate(BitmapHeapScanState *node,
|
|
ParallelContext *pcxt)
|
|
{
|
|
EState *estate = node->ss.ps.state;
|
|
|
|
node->pscan_len = add_size(offsetof(ParallelBitmapHeapState,
|
|
phs_snapshot_data),
|
|
EstimateSnapshotSpace(estate->es_snapshot));
|
|
|
|
shm_toc_estimate_chunk(&pcxt->estimator, node->pscan_len);
|
|
shm_toc_estimate_keys(&pcxt->estimator, 1);
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecBitmapHeapInitializeDSM
|
|
*
|
|
* Set up a parallel bitmap heap scan descriptor.
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
|
|
ParallelContext *pcxt)
|
|
{
|
|
ParallelBitmapHeapState *pstate;
|
|
EState *estate = node->ss.ps.state;
|
|
dsa_area *dsa = node->ss.ps.state->es_query_dsa;
|
|
|
|
/* If there's no DSA, there are no workers; initialize nothing. */
|
|
if (dsa == NULL)
|
|
return;
|
|
|
|
pstate = shm_toc_allocate(pcxt->toc, node->pscan_len);
|
|
|
|
pstate->tbmiterator = 0;
|
|
pstate->prefetch_iterator = 0;
|
|
|
|
/* Initialize the mutex */
|
|
SpinLockInit(&pstate->mutex);
|
|
pstate->prefetch_pages = 0;
|
|
pstate->prefetch_target = 0;
|
|
pstate->state = BM_INITIAL;
|
|
|
|
ConditionVariableInit(&pstate->cv);
|
|
SerializeSnapshot(estate->es_snapshot, pstate->phs_snapshot_data);
|
|
|
|
shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pstate);
|
|
node->pstate = pstate;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecBitmapHeapReInitializeDSM
|
|
*
|
|
* Reset shared state before beginning a fresh scan.
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecBitmapHeapReInitializeDSM(BitmapHeapScanState *node,
|
|
ParallelContext *pcxt)
|
|
{
|
|
ParallelBitmapHeapState *pstate = node->pstate;
|
|
dsa_area *dsa = node->ss.ps.state->es_query_dsa;
|
|
|
|
/* If there's no DSA, there are no workers; do nothing. */
|
|
if (dsa == NULL)
|
|
return;
|
|
|
|
pstate->state = BM_INITIAL;
|
|
|
|
if (DsaPointerIsValid(pstate->tbmiterator))
|
|
tbm_free_shared_area(dsa, pstate->tbmiterator);
|
|
|
|
if (DsaPointerIsValid(pstate->prefetch_iterator))
|
|
tbm_free_shared_area(dsa, pstate->prefetch_iterator);
|
|
|
|
pstate->tbmiterator = InvalidDsaPointer;
|
|
pstate->prefetch_iterator = InvalidDsaPointer;
|
|
}
|
|
|
|
/* ----------------------------------------------------------------
|
|
* ExecBitmapHeapInitializeWorker
|
|
*
|
|
* Copy relevant information from TOC into planstate.
|
|
* ----------------------------------------------------------------
|
|
*/
|
|
void
|
|
ExecBitmapHeapInitializeWorker(BitmapHeapScanState *node,
|
|
ParallelWorkerContext *pwcxt)
|
|
{
|
|
ParallelBitmapHeapState *pstate;
|
|
Snapshot snapshot;
|
|
|
|
Assert(node->ss.ps.state->es_query_dsa != NULL);
|
|
|
|
pstate = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
|
|
node->pstate = pstate;
|
|
|
|
snapshot = RestoreSnapshot(pstate->phs_snapshot_data);
|
|
table_scan_update_snapshot(node->ss.ss_currentScanDesc, snapshot);
|
|
}
|