On Mon, Feb 24, 2025 at 11:18 AM Melanie Plageman <melanieplage...@gmail.com> wrote: > > I changed my mind. I think since the struct I added was only used for > tbm_extract_page_tuple(), it was a bit weird. I also think it is okay > for callers to use TBM_MAX_TUPLES_PER_PAGE. I ended up revising this > to use the same API you implemented for TIDStore in > TidStoreGetBlockOffsets(). The caller passes an array and the size of > the array and tbm_extract_page_tuple() fills in that many offsets and > returns the total number of offsets. It avoids adding a new struct and > means callers could pass a different value than > TBM_MAX_TUPLES_PER_PAGE. Overall, I like it.
Okay, I've pushed those patches. All that remains in attached v34 are the patches to implement using the read stream API. I'll wait to push until the patches to modify the read stream API sequential detection are in. I was thinking about what the default value should be for effective_io_concurrency, and I looked back at Tomas' results. It definitely should be > 1. But, there are cases where 16 is a regression. So, perhaps it would be good to run some tests trying out 4 and 8 once we have a fixed up sequential detection algorithm. - Melanie
From 6cf32ed8b43492e6b47a6470ccdea7d09e2db481 Mon Sep 17 00:00:00 2001 From: Melanie Plageman <melanieplage...@gmail.com> Date: Fri, 21 Feb 2025 15:15:47 -0500 Subject: [PATCH v34 2/3] BitmapHeapScan uses the read stream API Make Bitmap Heap Scan use the read stream API instead of invoking ReadBuffer() for each block indicated by the bitmap. The read stream API handles prefetching, so remove all of the explicit prefetching from bitmap heap scan code. Now, heap table AM implements a read stream callback which uses the bitmap iterator to return the next required block to the read stream code. Reviewed-by: Tomas Vondra <to...@vondra.me> Discussion: https://postgr.es/m/d4bb26c9-fe07-439e-ac53-c0e244387e01%40vondra.me --- src/backend/access/heap/heapam.c | 80 +++++ src/backend/access/heap/heapam_handler.c | 90 +++--- src/backend/executor/nodeBitmapHeapscan.c | 341 +--------------------- src/include/access/tableam.h | 25 +- src/include/nodes/execnodes.h | 23 +- 5 files changed, 124 insertions(+), 435 deletions(-) diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index fa7935a0ed3..65e44b25b74 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -279,6 +279,72 @@ heap_scan_stream_read_next_serial(ReadStream *stream, return scan->rs_prefetch_block; } +/* + * Read stream API callback for bitmap heap scans. + * Returns the next block the caller wants from the read stream or + * InvalidBlockNumber when done. + */ +static BlockNumber +bitmapheap_stream_read_next(ReadStream *pgsr, void *private_data, + void *per_buffer_data) +{ + TBMIterateResult *tbmres = per_buffer_data; + BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) private_data; + HeapScanDesc hscan = (HeapScanDesc) bscan; + TableScanDesc sscan = &hscan->rs_base; + + for (;;) + { + CHECK_FOR_INTERRUPTS(); + + /* no more entries in the bitmap */ + if (!tbm_iterate(&sscan->st.rs_tbmiterator, tbmres)) + return InvalidBlockNumber; + + /* + * Ignore any claimed entries past what we think is the end of the + * relation. It may have been extended after the start of our scan (we + * only hold an AccessShareLock, and it could be inserts from this + * backend). We don't take this optimization in SERIALIZABLE + * isolation though, as we need to examine all invisible tuples + * reachable by the index. + */ + if (!IsolationIsSerializable() && + tbmres->blockno >= hscan->rs_nblocks) + continue; + + /* + * We can skip fetching the heap page if we don't need any fields from + * the heap, the bitmap entries don't need rechecking, and all tuples + * on the page are visible to our transaction. + */ + if (!(sscan->rs_flags & SO_NEED_TUPLES) && + !tbmres->recheck && + VM_ALL_VISIBLE(sscan->rs_rd, tbmres->blockno, &bscan->rs_vmbuffer)) + { + OffsetNumber offsets[TBM_MAX_TUPLES_PER_PAGE]; + int noffsets; + + /* can't be lossy in the skip_fetch case */ + Assert(!tbmres->lossy); + Assert(bscan->rs_empty_tuples_pending >= 0); + + /* + * We throw away the offsets, but this is the easiest way to get a + * count of tuples. + */ + noffsets = tbm_extract_page_tuple(tbmres, offsets, TBM_MAX_TUPLES_PER_PAGE); + bscan->rs_empty_tuples_pending += noffsets; + continue; + } + + return tbmres->blockno; + } + + /* not reachable */ + Assert(false); +} + /* ---------------- * initscan - scan code common to heap_beginscan and heap_rescan * ---------------- @@ -1067,6 +1133,7 @@ heap_beginscan(Relation relation, Snapshot snapshot, scan->rs_base.rs_flags = flags; scan->rs_base.rs_parallel = parallel_scan; scan->rs_strategy = NULL; /* set in initscan */ + scan->rs_cbuf = InvalidBuffer; /* * Disable page-at-a-time mode if it's not a MVCC-safe snapshot. @@ -1146,6 +1213,16 @@ heap_beginscan(Relation relation, Snapshot snapshot, scan, 0); } + else if (scan->rs_base.rs_flags & SO_TYPE_BITMAPSCAN) + { + scan->rs_read_stream = read_stream_begin_relation(READ_STREAM_DEFAULT, + scan->rs_strategy, + scan->rs_base.rs_rd, + MAIN_FORKNUM, + bitmapheap_stream_read_next, + scan, + sizeof(TBMIterateResult)); + } return (TableScanDesc) scan; @@ -1180,7 +1257,10 @@ heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params, * unpin scan buffers */ if (BufferIsValid(scan->rs_cbuf)) + { ReleaseBuffer(scan->rs_cbuf); + scan->rs_cbuf = InvalidBuffer; + } if (scan->rs_base.rs_flags & SO_TYPE_BITMAPSCAN) { diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c index ff1d8085883..0f7dd79f28e 100644 --- a/src/backend/access/heap/heapam_handler.c +++ b/src/backend/access/heap/heapam_handler.c @@ -2117,82 +2117,72 @@ heapam_estimate_rel_size(Relation rel, int32 *attr_widths, static bool heapam_scan_bitmap_next_block(TableScanDesc scan, - BlockNumber *blockno, bool *recheck, + bool *recheck, uint64 *lossy_pages, uint64 *exact_pages) { BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan; HeapScanDesc hscan = (HeapScanDesc) bscan; BlockNumber block; + void *per_buffer_data; Buffer buffer; Snapshot snapshot; int ntup; - TBMIterateResult tbmres; + TBMIterateResult *tbmres; OffsetNumber offsets[TBM_MAX_TUPLES_PER_PAGE]; int noffsets = -1; Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN); + Assert(hscan->rs_read_stream); hscan->rs_cindex = 0; hscan->rs_ntuples = 0; - *blockno = InvalidBlockNumber; - *recheck = true; - - do + /* Release buffer containing previous block. */ + if (BufferIsValid(hscan->rs_cbuf)) { - CHECK_FOR_INTERRUPTS(); + ReleaseBuffer(hscan->rs_cbuf); + hscan->rs_cbuf = InvalidBuffer; + } - if (!tbm_iterate(&scan->st.rs_tbmiterator, &tbmres)) - return false; + hscan->rs_cbuf = read_stream_next_buffer(hscan->rs_read_stream, + &per_buffer_data); - /* Exact pages need their tuple offsets extracted. */ - if (!tbmres.lossy) - noffsets = tbm_extract_page_tuple(&tbmres, offsets, - TBM_MAX_TUPLES_PER_PAGE); + if (BufferIsInvalid(hscan->rs_cbuf)) + { + if (BufferIsValid(bscan->rs_vmbuffer)) + { + ReleaseBuffer(bscan->rs_vmbuffer); + bscan->rs_vmbuffer = InvalidBuffer; + } /* - * Ignore any claimed entries past what we think is the end of the - * relation. It may have been extended after the start of our scan (we - * only hold an AccessShareLock, and it could be inserts from this - * backend). We don't take this optimization in SERIALIZABLE - * isolation though, as we need to examine all invisible tuples - * reachable by the index. + * Bitmap is exhausted. Time to emit empty tuples if relevant. We emit + * all empty tuples at the end instead of emitting them per block we + * skip fetching. This is necessary because the streaming read API + * will only return TBMIterateResults for blocks actually fetched. + * When we skip fetching a block, we keep track of how many empty + * tuples to emit at the end of the BitmapHeapScan. We do not recheck + * all NULL tuples. */ - } while (!IsolationIsSerializable() && - tbmres.blockno >= hscan->rs_nblocks); + *recheck = false; + return bscan->rs_empty_tuples_pending > 0; + } - /* Got a valid block */ - *blockno = tbmres.blockno; - *recheck = tbmres.recheck; + Assert(per_buffer_data); - /* - * We can skip fetching the heap page if we don't need any fields from the - * heap, the bitmap entries don't need rechecking, and all tuples on the - * page are visible to our transaction. - */ - if (!(scan->rs_flags & SO_NEED_TUPLES) && - !tbmres.recheck && - VM_ALL_VISIBLE(scan->rs_rd, tbmres.blockno, &bscan->rs_vmbuffer)) - { - /* can't be lossy in the skip_fetch case */ - Assert(!tbmres.lossy); - Assert(bscan->rs_empty_tuples_pending >= 0); - Assert(noffsets > -1); + tbmres = per_buffer_data; - bscan->rs_empty_tuples_pending += noffsets; + Assert(BlockNumberIsValid(tbmres->blockno)); + Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno); - return true; - } + /* Exact pages need their tuple offsets extracted. */ + if (!tbmres->lossy) + noffsets = tbm_extract_page_tuple(tbmres, offsets, + TBM_MAX_TUPLES_PER_PAGE); - block = tbmres.blockno; + *recheck = tbmres->recheck; - /* - * Acquire pin on the target heap page, trading in any pin we held before. - */ - hscan->rs_cbuf = ReleaseAndReadBuffer(hscan->rs_cbuf, - scan->rs_rd, - block); - hscan->rs_cblock = block; + block = hscan->rs_cblock = tbmres->blockno; buffer = hscan->rs_cbuf; snapshot = scan->rs_snapshot; @@ -2213,7 +2203,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, /* * We need two separate strategies for lossy and non-lossy cases. */ - if (!tbmres.lossy) + if (!tbmres->lossy) { /* * Bitmap is non-lossy, so we just look through the offsets listed in @@ -2277,7 +2267,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, Assert(ntup <= MaxHeapTuplesPerPage); hscan->rs_ntuples = ntup; - if (tbmres.lossy) + if (tbmres->lossy) (*lossy_pages)++; else (*exact_pages)++; diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c index 3b4ea0f6144..6df34094a13 100644 --- a/src/backend/executor/nodeBitmapHeapscan.c +++ b/src/backend/executor/nodeBitmapHeapscan.c @@ -51,10 +51,6 @@ static void BitmapTableScanSetup(BitmapHeapScanState *node); static TupleTableSlot *BitmapHeapNext(BitmapHeapScanState *node); static inline void BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate); -static inline void BitmapAdjustPrefetchIterator(BitmapHeapScanState *node); -static inline void BitmapAdjustPrefetchTarget(BitmapHeapScanState *node); -static inline void BitmapPrefetch(BitmapHeapScanState *node, - TableScanDesc scan); static bool BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate); @@ -62,14 +58,6 @@ static bool BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate); * Do the underlying index scan, build the bitmap, set up the parallel state * needed for parallel workers to iterate through the bitmap, and set up the * underlying table scan descriptor. - * - * For prefetching, we use *two* iterators, one for the pages we are actually - * scanning and another that runs ahead of the first for prefetching. - * node->prefetch_pages tracks exactly how many pages ahead the prefetch - * iterator is. Also, node->prefetch_target tracks the desired prefetch - * distance, which starts small and increases up to the - * node->prefetch_maximum. This is to avoid doing a lot of prefetching in a - * scan that stops after a few tuples because of a LIMIT. */ static void BitmapTableScanSetup(BitmapHeapScanState *node) @@ -102,14 +90,6 @@ BitmapTableScanSetup(BitmapHeapScanState *node) */ pstate->tbmiterator = tbm_prepare_shared_iterate(node->tbm); -#ifdef USE_PREFETCH - if (node->prefetch_maximum > 0) - { - pstate->prefetch_iterator = - tbm_prepare_shared_iterate(node->tbm); - } -#endif /* USE_PREFETCH */ - /* We have initialized the shared state so wake up others. */ BitmapDoneInitializingSharedState(pstate); } @@ -119,15 +99,6 @@ BitmapTableScanSetup(BitmapHeapScanState *node) pstate->tbmiterator : InvalidDsaPointer); -#ifdef USE_PREFETCH - if (node->prefetch_maximum > 0) - node->prefetch_iterator = - tbm_begin_iterate(node->tbm, dsa, - pstate ? - pstate->prefetch_iterator : - InvalidDsaPointer); -#endif /* USE_PREFETCH */ - /* * If this is the first scan of the underlying table, create the table * scan descriptor and begin the scan. @@ -158,7 +129,6 @@ BitmapTableScanSetup(BitmapHeapScanState *node) node->initialized = true; } - /* ---------------------------------------------------------------- * BitmapHeapNext * @@ -172,10 +142,6 @@ BitmapHeapNext(BitmapHeapScanState *node) TableScanDesc scan; TupleTableSlot *slot; -#ifdef USE_PREFETCH - ParallelBitmapHeapState *pstate = node->pstate; -#endif - /* * extract necessary information from index scan node */ @@ -204,37 +170,6 @@ BitmapHeapNext(BitmapHeapScanState *node) CHECK_FOR_INTERRUPTS(); -#ifdef USE_PREFETCH - - /* - * Try to prefetch at least a few pages even before we get to the - * second page if we don't stop reading after the first tuple. - */ - if (!pstate) - { - if (node->prefetch_target < node->prefetch_maximum) - node->prefetch_target++; - } - else if (pstate->prefetch_target < node->prefetch_maximum) - { - /* take spinlock while updating shared state */ - SpinLockAcquire(&pstate->mutex); - if (pstate->prefetch_target < node->prefetch_maximum) - pstate->prefetch_target++; - SpinLockRelease(&pstate->mutex); - } -#endif /* USE_PREFETCH */ - - /* - * We issue prefetch requests *after* fetching the current page to - * try to avoid having prefetching interfere with the main I/O. - * Also, this should happen only when we have determined there is - * still something to do on the current page, else we may - * uselessly prefetch the same page we are just about to request - * for real. - */ - BitmapPrefetch(node, scan); - /* * If we are using lossy info, we have to recheck the qual * conditions at every tuple. @@ -257,31 +192,15 @@ BitmapHeapNext(BitmapHeapScanState *node) new_page: - BitmapAdjustPrefetchIterator(node); - /* * Returns false if the bitmap is exhausted and there are no further * blocks we need to scan. */ - if (!table_scan_bitmap_next_block(scan, &node->blockno, + if (!table_scan_bitmap_next_block(scan, &node->recheck, &node->stats.lossy_pages, &node->stats.exact_pages)) break; - - /* - * If serial, we can error out if the prefetch block doesn't stay - * ahead of the current block. - */ - if (node->pstate == NULL && - !tbm_exhausted(&node->prefetch_iterator) && - node->prefetch_blockno < node->blockno) - elog(ERROR, - "prefetch and main iterators are out of sync. pfblockno: %d. blockno: %d", - node->prefetch_blockno, node->blockno); - - /* Adjust the prefetch target */ - BitmapAdjustPrefetchTarget(node); } /* @@ -305,225 +224,6 @@ BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate) ConditionVariableBroadcast(&pstate->cv); } -/* - * BitmapAdjustPrefetchIterator - Adjust the prefetch iterator - * - * We keep track of how far the prefetch iterator is ahead of the main - * iterator in prefetch_pages. For each block the main iterator returns, we - * decrement prefetch_pages. - */ -static inline void -BitmapAdjustPrefetchIterator(BitmapHeapScanState *node) -{ -#ifdef USE_PREFETCH - ParallelBitmapHeapState *pstate = node->pstate; - TBMIterateResult tbmpre; - - 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 (!tbm_exhausted(prefetch_iterator)) - { - tbm_iterate(prefetch_iterator, &tbmpre); - node->prefetch_blockno = tbmpre.blockno; - } - return; - } - - /* - * XXX: There is a known issue with keeping the prefetch and current block - * iterators in sync for parallel bitmap table scans. This can lead to - * prefetching blocks that have already been read. See the discussion - * here: - * https://postgr.es/m/20240315211449.en2jcmdqxv5o6tlz%40alap3.anarazel.de - * Note that moving the call site of BitmapAdjustPrefetchIterator() - * exacerbates the effects of this bug. - */ - if (node->prefetch_maximum > 0) - { - TBMIterator *prefetch_iterator = &node->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 (!tbm_exhausted(prefetch_iterator)) - { - tbm_iterate(prefetch_iterator, &tbmpre); - node->prefetch_blockno = tbmpre.blockno; - } - } - } -#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 (!tbm_exhausted(prefetch_iterator)) - { - while (node->prefetch_pages < node->prefetch_target) - { - TBMIterateResult tbmpre; - bool skip_fetch; - - if (!tbm_iterate(prefetch_iterator, &tbmpre)) - { - /* No more pages to prefetch */ - Assert(!BlockNumberIsValid(tbmpre.blockno)); - tbm_end_iterate(prefetch_iterator); - break; - } - node->prefetch_pages++; - node->prefetch_blockno = tbmpre.blockno; - - /* - * 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?) - */ - skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) && - !tbmpre.recheck && - 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) - { - TBMIterator *prefetch_iterator = &node->prefetch_iterator; - - if (!tbm_exhausted(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; - - if (!tbm_iterate(prefetch_iterator, &tbmpre)) - { - Assert(!BlockNumberIsValid(tbmpre.blockno)); - /* No more pages to prefetch */ - tbm_end_iterate(prefetch_iterator); - break; - } - - node->prefetch_blockno = tbmpre.blockno; - - /* As above, skip prefetch if we expect not to need page */ - skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) && - !tbmpre.recheck && - 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 */ @@ -580,24 +280,12 @@ ExecReScanBitmapHeapScan(BitmapHeapScanState *node) table_rescan(node->ss.ss_currentScanDesc, NULL); } - /* If we did not already clean up the prefetch iterator, do so now. */ - if (!tbm_exhausted(&node->prefetch_iterator)) - tbm_end_iterate(&node->prefetch_iterator); - /* release bitmaps and buffers if any */ if (node->tbm) tbm_free(node->tbm); - if (node->pvmbuffer != InvalidBuffer) - ReleaseBuffer(node->pvmbuffer); node->tbm = NULL; node->initialized = false; - node->pvmbuffer = InvalidBuffer; node->recheck = true; - /* Only used for serial BHS */ - node->blockno = InvalidBlockNumber; - node->prefetch_blockno = InvalidBlockNumber; - node->prefetch_pages = 0; - node->prefetch_target = -1; ExecScanReScan(&node->ss); @@ -666,17 +354,11 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node) table_endscan(scanDesc); } - /* If we did not already clean up the prefetch iterator, do so now. */ - if (!tbm_exhausted(&node->prefetch_iterator)) - tbm_end_iterate(&node->prefetch_iterator); - /* * release bitmaps and buffers if any */ if (node->tbm) tbm_free(node->tbm); - if (node->pvmbuffer != InvalidBuffer) - ReleaseBuffer(node->pvmbuffer); } /* ---------------------------------------------------------------- @@ -709,18 +391,13 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags) scanstate->ss.ps.ExecProcNode = ExecBitmapHeapScan; scanstate->tbm = NULL; - scanstate->pvmbuffer = InvalidBuffer; /* Zero the statistics counters */ memset(&scanstate->stats, 0, sizeof(BitmapHeapScanInstrumentation)); - scanstate->prefetch_pages = 0; - scanstate->prefetch_target = -1; scanstate->initialized = false; scanstate->pstate = NULL; scanstate->recheck = true; - scanstate->blockno = InvalidBlockNumber; - scanstate->prefetch_blockno = InvalidBlockNumber; /* * Miscellaneous initialization @@ -760,13 +437,6 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags) scanstate->bitmapqualorig = ExecInitQual(node->bitmapqualorig, (PlanState *) scanstate); - /* - * Maximum number of prefetches for the tablespace if configured, - * otherwise the current value of the effective_io_concurrency GUC. - */ - scanstate->prefetch_maximum = - get_tablespace_io_concurrency(currentRelation->rd_rel->reltablespace); - scanstate->ss.ss_currentRelation = currentRelation; /* @@ -870,12 +540,9 @@ ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node, sinstrument = (SharedBitmapHeapInstrumentation *) ptr; pstate->tbmiterator = 0; - pstate->prefetch_iterator = 0; /* Initialize the mutex */ SpinLockInit(&pstate->mutex); - pstate->prefetch_pages = 0; - pstate->prefetch_target = -1; pstate->state = BM_INITIAL; ConditionVariableInit(&pstate->cv); @@ -912,17 +579,11 @@ ExecBitmapHeapReInitializeDSM(BitmapHeapScanState *node, return; pstate->state = BM_INITIAL; - pstate->prefetch_pages = 0; - pstate->prefetch_target = -1; 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; } /* ---------------------------------------------------------------- diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h index 131c050c15f..507d4ebe68f 100644 --- a/src/include/access/tableam.h +++ b/src/include/access/tableam.h @@ -797,28 +797,12 @@ typedef struct TableAmRoutine * always need to be rechecked, but some non-lossy pages' tuples may also * require recheck. * - * `blockno` is the current block and is set by the table AM. The table AM - * is responsible for advancing the main iterator, but the bitmap table - * scan code still advances the prefetch iterator. `blockno` is used by - * bitmap table scan code to validate that the prefetch block stays ahead - * of the current block. - * - * XXX: Currently this may only be implemented if the AM uses md.c as its - * storage manager, and uses ItemPointer->ip_blkid in a manner that maps - * blockids directly to the underlying storage. nodeBitmapHeapscan.c - * performs prefetching directly using that interface. This probably - * needs to be rectified at a later point. - * - * XXX: Currently this may only be implemented if the AM uses the - * visibilitymap, as nodeBitmapHeapscan.c unconditionally accesses it to - * perform prefetching. This probably needs to be rectified at a later - * point. + * Prefetching additional data from the bitmap is left to the table AM. * * Optional callback, but either both scan_bitmap_next_block and * scan_bitmap_next_tuple need to exist, or neither. */ bool (*scan_bitmap_next_block) (TableScanDesc scan, - BlockNumber *blockno, bool *recheck, uint64 *lossy_pages, uint64 *exact_pages); @@ -1966,16 +1950,11 @@ table_relation_estimate_size(Relation rel, int32 *attr_widths, * `recheck` is set by the table AM to indicate whether or not the tuples * from this block should be rechecked. * - * `blockno` is the current block and is set by the table AM and is used by - * bitmap table scan code to validate that the prefetch block stays ahead of - * the current block. - * * Note, this is an optionally implemented function, therefore should only be * used after verifying the presence (at plan time or such). */ static inline bool table_scan_bitmap_next_block(TableScanDesc scan, - BlockNumber *blockno, bool *recheck, uint64 *lossy_pages, uint64 *exact_pages) @@ -1989,7 +1968,7 @@ table_scan_bitmap_next_block(TableScanDesc scan, elog(ERROR, "unexpected table_scan_bitmap_next_block call during logical decoding"); return scan->rs_rd->rd_tableam->scan_bitmap_next_block(scan, - blockno, recheck, + recheck, lossy_pages, exact_pages); } diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index a323fa98bbb..5f743d6699c 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -1828,11 +1828,7 @@ typedef enum /* ---------------- * ParallelBitmapHeapState information * tbmiterator iterator for scanning current pages - * prefetch_iterator iterator for prefetching ahead of current page - * mutex mutual exclusion for the prefetching variable - * and state - * prefetch_pages # pages prefetch iterator is ahead of current - * prefetch_target current target prefetch distance + * mutex mutual exclusion for state * state current state of the TIDBitmap * cv conditional wait variable * ---------------- @@ -1840,10 +1836,7 @@ typedef enum typedef struct ParallelBitmapHeapState { dsa_pointer tbmiterator; - dsa_pointer prefetch_iterator; slock_t mutex; - int prefetch_pages; - int prefetch_target; SharedBitmapState state; ConditionVariable cv; } ParallelBitmapHeapState; @@ -1867,18 +1860,11 @@ typedef struct SharedBitmapHeapInstrumentation * * bitmapqualorig execution state for bitmapqualorig expressions * tbm bitmap obtained from child index scan(s) - * pvmbuffer buffer for visibility-map lookups of prefetched pages * stats execution statistics - * prefetch_iterator iterator for prefetching ahead of current page - * prefetch_pages # pages prefetch iterator is ahead of current - * prefetch_target current target prefetch distance - * prefetch_maximum maximum value for prefetch_target * initialized is node is ready to iterate * pstate shared state for parallel bitmap scan * sinstrument statistics for parallel workers * recheck do current page's tuples need recheck - * blockno used to validate pf and current block stay in sync - * prefetch_blockno used to validate pf stays ahead of current block * ---------------- */ typedef struct BitmapHeapScanState @@ -1886,18 +1872,11 @@ typedef struct BitmapHeapScanState ScanState ss; /* its first field is NodeTag */ ExprState *bitmapqualorig; TIDBitmap *tbm; - Buffer pvmbuffer; BitmapHeapScanInstrumentation stats; - TBMIterator prefetch_iterator; - int prefetch_pages; - int prefetch_target; - int prefetch_maximum; bool initialized; ParallelBitmapHeapState *pstate; SharedBitmapHeapInstrumentation *sinstrument; bool recheck; - BlockNumber blockno; - BlockNumber prefetch_blockno; } BitmapHeapScanState; /* ---------------- -- 2.34.1
From 4965e11fedbd22cc05643b72acb4325a0a1b1654 Mon Sep 17 00:00:00 2001 From: Melanie Plageman <melanieplage...@gmail.com> Date: Thu, 20 Feb 2025 12:30:26 -0500 Subject: [PATCH v34 1/3] Separate TBM[Shared|Private]Iterator and TBMIterateResult Remove the TBMIterateResult member from the TBMPrivateIterator and TBMSharedIterator and make tbm_[shared|private_]iterate() take a TBMIterateResult as a parameter. This allows tidbitmap API users to manage multiple TBMIterateResults per scan. This is required for bitmap heap scan to use the read stream API, with which there may be multiple I/Os in flight at once, each one with a TBMIterateResult. Reviewed-by: Tomas Vondra <to...@vondra.me> Discussion: https://postgr.es/m/d4bb26c9-fe07-439e-ac53-c0e244387e01%40vondra.me --- src/backend/access/gin/ginget.c | 33 ++++---- src/backend/access/gin/ginscan.c | 2 +- src/backend/access/heap/heapam_handler.c | 28 +++---- src/backend/executor/nodeBitmapHeapscan.c | 39 +++++---- src/backend/nodes/tidbitmap.c | 96 ++++++++++++----------- src/include/access/gin_private.h | 7 +- src/include/nodes/tidbitmap.h | 6 +- 7 files changed, 110 insertions(+), 101 deletions(-) diff --git a/src/backend/access/gin/ginget.c b/src/backend/access/gin/ginget.c index f3b19d280c3..791bc70ec26 100644 --- a/src/backend/access/gin/ginget.c +++ b/src/backend/access/gin/ginget.c @@ -332,8 +332,8 @@ restartScanEntry: entry->list = NULL; entry->nlist = 0; entry->matchBitmap = NULL; - entry->matchResult = NULL; entry->matchNtuples = -1; + entry->matchResult.blockno = InvalidBlockNumber; entry->reduceResult = false; entry->predictNumberResult = 0; @@ -825,20 +825,19 @@ entryGetItem(GinState *ginstate, GinScanEntry entry, { /* * If we've exhausted all items on this block, move to next block - * in the bitmap. + * in the bitmap. tbm_private_iterate() sets matchResult.blockno + * to InvalidBlockNumber when the bitmap is exhausted. */ - while (entry->matchResult == NULL || - (!entry->matchResult->lossy && + while ((!BlockNumberIsValid(entry->matchResult.blockno)) || + (!entry->matchResult.lossy && entry->offset >= entry->matchNtuples) || - entry->matchResult->blockno < advancePastBlk || + entry->matchResult.blockno < advancePastBlk || (ItemPointerIsLossyPage(&advancePast) && - entry->matchResult->blockno == advancePastBlk)) + entry->matchResult.blockno == advancePastBlk)) { - entry->matchResult = - tbm_private_iterate(entry->matchIterator); - - if (entry->matchResult == NULL) + if (!tbm_private_iterate(entry->matchIterator, &entry->matchResult)) { + Assert(!BlockNumberIsValid(entry->matchResult.blockno)); ItemPointerSetInvalid(&entry->curItem); tbm_end_private_iterate(entry->matchIterator); entry->matchIterator = NULL; @@ -847,14 +846,14 @@ entryGetItem(GinState *ginstate, GinScanEntry entry, } /* Exact pages need their tuple offsets extracted. */ - if (!entry->matchResult->lossy) - entry->matchNtuples = tbm_extract_page_tuple(entry->matchResult, + if (!entry->matchResult.lossy) + entry->matchNtuples = tbm_extract_page_tuple(&entry->matchResult, entry->matchOffsets, TBM_MAX_TUPLES_PER_PAGE); /* * Reset counter to the beginning of entry->matchResult. Note: - * entry->offset is still greater than entry->matchNtuples if + * entry->offset is still greater than matchResult.ntuples if * matchResult is lossy. So, on next call we will get next * result from TIDBitmap. */ @@ -867,10 +866,10 @@ entryGetItem(GinState *ginstate, GinScanEntry entry, * We're now on the first page after advancePast which has any * items on it. If it's a lossy result, return that. */ - if (entry->matchResult->lossy) + if (entry->matchResult.lossy) { ItemPointerSetLossyPage(&entry->curItem, - entry->matchResult->blockno); + entry->matchResult.blockno); /* * We might as well fall out of the loop; we could not @@ -887,7 +886,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry, Assert(entry->matchNtuples > -1); /* Skip over any offsets <= advancePast, and return that. */ - if (entry->matchResult->blockno == advancePastBlk) + if (entry->matchResult.blockno == advancePastBlk) { Assert(entry->matchNtuples > 0); @@ -908,7 +907,7 @@ entryGetItem(GinState *ginstate, GinScanEntry entry, } ItemPointerSet(&entry->curItem, - entry->matchResult->blockno, + entry->matchResult.blockno, entry->matchOffsets[entry->offset]); entry->offset++; diff --git a/src/backend/access/gin/ginscan.c b/src/backend/access/gin/ginscan.c index 63ded6301e2..f033417e5a8 100644 --- a/src/backend/access/gin/ginscan.c +++ b/src/backend/access/gin/ginscan.c @@ -106,7 +106,7 @@ ginFillScanEntry(GinScanOpaque so, OffsetNumber attnum, ItemPointerSetMin(&scanEntry->curItem); scanEntry->matchBitmap = NULL; scanEntry->matchIterator = NULL; - scanEntry->matchResult = NULL; + scanEntry->matchResult.blockno = InvalidBlockNumber; scanEntry->matchNtuples = -1; scanEntry->list = NULL; scanEntry->nlist = 0; diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c index e78682c3cef..ff1d8085883 100644 --- a/src/backend/access/heap/heapam_handler.c +++ b/src/backend/access/heap/heapam_handler.c @@ -2126,7 +2126,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, Buffer buffer; Snapshot snapshot; int ntup; - TBMIterateResult *tbmres; + TBMIterateResult tbmres; OffsetNumber offsets[TBM_MAX_TUPLES_PER_PAGE]; int noffsets = -1; @@ -2142,14 +2142,12 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, { CHECK_FOR_INTERRUPTS(); - tbmres = tbm_iterate(&scan->st.rs_tbmiterator); - - if (tbmres == NULL) + if (!tbm_iterate(&scan->st.rs_tbmiterator, &tbmres)) return false; /* Exact pages need their tuple offsets extracted. */ - if (!tbmres->lossy) - noffsets = tbm_extract_page_tuple(tbmres, offsets, + if (!tbmres.lossy) + noffsets = tbm_extract_page_tuple(&tbmres, offsets, TBM_MAX_TUPLES_PER_PAGE); /* @@ -2161,11 +2159,11 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, * reachable by the index. */ } while (!IsolationIsSerializable() && - tbmres->blockno >= hscan->rs_nblocks); + tbmres.blockno >= hscan->rs_nblocks); /* Got a valid block */ - *blockno = tbmres->blockno; - *recheck = tbmres->recheck; + *blockno = tbmres.blockno; + *recheck = tbmres.recheck; /* * We can skip fetching the heap page if we don't need any fields from the @@ -2173,11 +2171,11 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, * page are visible to our transaction. */ if (!(scan->rs_flags & SO_NEED_TUPLES) && - !tbmres->recheck && - VM_ALL_VISIBLE(scan->rs_rd, tbmres->blockno, &bscan->rs_vmbuffer)) + !tbmres.recheck && + VM_ALL_VISIBLE(scan->rs_rd, tbmres.blockno, &bscan->rs_vmbuffer)) { /* can't be lossy in the skip_fetch case */ - Assert(!tbmres->lossy); + Assert(!tbmres.lossy); Assert(bscan->rs_empty_tuples_pending >= 0); Assert(noffsets > -1); @@ -2186,7 +2184,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, return true; } - block = tbmres->blockno; + block = tbmres.blockno; /* * Acquire pin on the target heap page, trading in any pin we held before. @@ -2215,7 +2213,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, /* * We need two separate strategies for lossy and non-lossy cases. */ - if (!tbmres->lossy) + if (!tbmres.lossy) { /* * Bitmap is non-lossy, so we just look through the offsets listed in @@ -2279,7 +2277,7 @@ heapam_scan_bitmap_next_block(TableScanDesc scan, Assert(ntup <= MaxHeapTuplesPerPage); hscan->rs_ntuples = ntup; - if (tbmres->lossy) + if (tbmres.lossy) (*lossy_pages)++; else (*exact_pages)++; diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c index be0d24d901b..3b4ea0f6144 100644 --- a/src/backend/executor/nodeBitmapHeapscan.c +++ b/src/backend/executor/nodeBitmapHeapscan.c @@ -317,7 +317,7 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node) { #ifdef USE_PREFETCH ParallelBitmapHeapState *pstate = node->pstate; - TBMIterateResult *tbmpre; + TBMIterateResult tbmpre; if (pstate == NULL) { @@ -330,9 +330,8 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node) } else if (!tbm_exhausted(prefetch_iterator)) { - tbmpre = tbm_iterate(prefetch_iterator); - node->prefetch_blockno = tbmpre ? tbmpre->blockno : - InvalidBlockNumber; + tbm_iterate(prefetch_iterator, &tbmpre); + node->prefetch_blockno = tbmpre.blockno; } return; } @@ -371,9 +370,8 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node) */ if (!tbm_exhausted(prefetch_iterator)) { - tbmpre = tbm_iterate(prefetch_iterator); - node->prefetch_blockno = tbmpre ? tbmpre->blockno : - InvalidBlockNumber; + tbm_iterate(prefetch_iterator, &tbmpre); + node->prefetch_blockno = tbmpre.blockno; } } } @@ -441,17 +439,18 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan) { while (node->prefetch_pages < node->prefetch_target) { - TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator); + TBMIterateResult tbmpre; bool skip_fetch; - if (tbmpre == NULL) + if (!tbm_iterate(prefetch_iterator, &tbmpre)) { /* No more pages to prefetch */ + Assert(!BlockNumberIsValid(tbmpre.blockno)); tbm_end_iterate(prefetch_iterator); break; } node->prefetch_pages++; - node->prefetch_blockno = tbmpre->blockno; + node->prefetch_blockno = tbmpre.blockno; /* * If we expect not to have to actually read this heap page, @@ -460,13 +459,13 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan) * prefetch_pages?) */ skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) && - !tbmpre->recheck && + !tbmpre.recheck && VM_ALL_VISIBLE(node->ss.ss_currentRelation, - tbmpre->blockno, + tbmpre.blockno, &node->pvmbuffer)); if (!skip_fetch) - PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno); + PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno); } } @@ -481,7 +480,7 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan) { while (1) { - TBMIterateResult *tbmpre; + TBMIterateResult tbmpre; bool do_prefetch = false; bool skip_fetch; @@ -500,25 +499,25 @@ BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan) if (!do_prefetch) return; - tbmpre = tbm_iterate(prefetch_iterator); - if (tbmpre == NULL) + if (!tbm_iterate(prefetch_iterator, &tbmpre)) { + Assert(!BlockNumberIsValid(tbmpre.blockno)); /* No more pages to prefetch */ tbm_end_iterate(prefetch_iterator); break; } - node->prefetch_blockno = tbmpre->blockno; + node->prefetch_blockno = tbmpre.blockno; /* As above, skip prefetch if we expect not to need page */ skip_fetch = (!(scan->rs_flags & SO_NEED_TUPLES) && - !tbmpre->recheck && + !tbmpre.recheck && VM_ALL_VISIBLE(node->ss.ss_currentRelation, - tbmpre->blockno, + tbmpre.blockno, &node->pvmbuffer)); if (!skip_fetch) - PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno); + PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre.blockno); } } } diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c index 3d835024caa..41031aa8f2f 100644 --- a/src/backend/nodes/tidbitmap.c +++ b/src/backend/nodes/tidbitmap.c @@ -172,7 +172,6 @@ struct TBMPrivateIterator int spageptr; /* next spages index */ int schunkptr; /* next schunks index */ int schunkbit; /* next bit to check in current schunk */ - TBMIterateResult output; }; /* @@ -213,7 +212,6 @@ struct TBMSharedIterator PTEntryArray *ptbase; /* pagetable element array */ PTIterationArray *ptpages; /* sorted exact page index list */ PTIterationArray *ptchunks; /* sorted lossy page index list */ - TBMIterateResult output; }; /* Local function prototypes */ @@ -957,21 +955,28 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp) /* * tbm_private_iterate - scan through next page of a TIDBitmap * - * Returns a TBMIterateResult representing one page, or NULL if there are - * no more pages to scan. Pages are guaranteed to be delivered in numerical - * order. If lossy is true, then the bitmap is "lossy" and failed to - * remember the exact tuples to look at on this page --- the caller must - * examine all tuples on the page and check if they meet the intended - * condition. result->ntuples is set to -1 when the bitmap is lossy. - * If result->recheck is true, only the indicated tuples need - * be examined, but the condition must be rechecked anyway. (For ease of - * testing, recheck is always set true when lossy is true.) + * Caller must pass in a TBMIterateResult to be filled. + * + * Pages are guaranteed to be delivered in numerical order. + * + * Returns false when there are no more pages to scan and true otherwise. When + * there are no more pages to scan, tbmres->blockno is set to + * InvalidBlockNumber. + * + * If lossy is true, then the bitmap is "lossy" and failed to remember + * the exact tuples to look at on this page --- the caller must examine all + * tuples on the page and check if they meet the intended condition. If lossy + * is false, the caller must later extract the tuple offsets from the page + * pointed to by internal_page with tbm_extract_page_tuple. + * + * If tbmres->recheck is true, only the indicated tuples need be examined, but + * the condition must be rechecked anyway. (For ease of testing, recheck is + * always set true when lossy is true.) */ -TBMIterateResult * -tbm_private_iterate(TBMPrivateIterator *iterator) +bool +tbm_private_iterate(TBMPrivateIterator *iterator, TBMIterateResult *tbmres) { TIDBitmap *tbm = iterator->tbm; - TBMIterateResult *output = &(iterator->output); Assert(tbm->iterating == TBM_ITERATING_PRIVATE); @@ -1009,12 +1014,12 @@ tbm_private_iterate(TBMPrivateIterator *iterator) chunk_blockno < tbm->spages[iterator->spageptr]->blockno) { /* Return a lossy page indicator from the chunk */ - output->blockno = chunk_blockno; - output->lossy = true; - output->recheck = true; - output->internal_page = NULL; + tbmres->blockno = chunk_blockno; + tbmres->lossy = true; + tbmres->recheck = true; + tbmres->internal_page = NULL; iterator->schunkbit++; - return output; + return true; } } @@ -1028,16 +1033,17 @@ tbm_private_iterate(TBMPrivateIterator *iterator) else page = tbm->spages[iterator->spageptr]; - output->internal_page = page; - output->blockno = page->blockno; - output->lossy = false; - output->recheck = page->recheck; + tbmres->internal_page = page; + tbmres->blockno = page->blockno; + tbmres->lossy = false; + tbmres->recheck = page->recheck; iterator->spageptr++; - return output; + return true; } /* Nothing more in the bitmap */ - return NULL; + tbmres->blockno = InvalidBlockNumber; + return false; } /* @@ -1047,10 +1053,9 @@ tbm_private_iterate(TBMPrivateIterator *iterator) * across multiple processes. We need to acquire the iterator LWLock, * before accessing the shared members. */ -TBMIterateResult * -tbm_shared_iterate(TBMSharedIterator *iterator) +bool +tbm_shared_iterate(TBMSharedIterator *iterator, TBMIterateResult *tbmres) { - TBMIterateResult *output = &iterator->output; TBMSharedIteratorState *istate = iterator->state; PagetableEntry *ptbase = NULL; int *idxpages = NULL; @@ -1101,14 +1106,14 @@ tbm_shared_iterate(TBMSharedIterator *iterator) chunk_blockno < ptbase[idxpages[istate->spageptr]].blockno) { /* Return a lossy page indicator from the chunk */ - output->blockno = chunk_blockno; - output->lossy = true; - output->recheck = true; - output->internal_page = NULL; + tbmres->blockno = chunk_blockno; + tbmres->lossy = true; + tbmres->recheck = true; + tbmres->internal_page = NULL; istate->schunkbit++; LWLockRelease(&istate->lock); - return output; + return true; } } @@ -1116,21 +1121,22 @@ tbm_shared_iterate(TBMSharedIterator *iterator) { PagetableEntry *page = &ptbase[idxpages[istate->spageptr]]; - output->internal_page = page; - output->blockno = page->blockno; - output->lossy = false; - output->recheck = page->recheck; + tbmres->internal_page = page; + tbmres->blockno = page->blockno; + tbmres->lossy = false; + tbmres->recheck = page->recheck; istate->spageptr++; LWLockRelease(&istate->lock); - return output; + return true; } LWLockRelease(&istate->lock); /* Nothing more in the bitmap */ - return NULL; + tbmres->blockno = InvalidBlockNumber; + return false; } /* @@ -1604,15 +1610,17 @@ tbm_end_iterate(TBMIterator *iterator) } /* - * Get the next TBMIterateResult from the shared or private bitmap iterator. + * Populate the next TBMIterateResult using the shared or private bitmap + * iterator. Returns false when there is nothing more to scan. */ -TBMIterateResult * -tbm_iterate(TBMIterator *iterator) +bool +tbm_iterate(TBMIterator *iterator, TBMIterateResult *tbmres) { Assert(iterator); + Assert(tbmres); if (iterator->shared) - return tbm_shared_iterate(iterator->i.shared_iterator); + return tbm_shared_iterate(iterator->i.shared_iterator, tbmres); else - return tbm_private_iterate(iterator->i.private_iterator); + return tbm_private_iterate(iterator->i.private_iterator, tbmres); } diff --git a/src/include/access/gin_private.h b/src/include/access/gin_private.h index 50478db9820..82d2c28583e 100644 --- a/src/include/access/gin_private.h +++ b/src/include/access/gin_private.h @@ -353,7 +353,12 @@ typedef struct GinScanEntryData /* for a partial-match or full-scan query, we accumulate all TIDs here */ TIDBitmap *matchBitmap; TBMPrivateIterator *matchIterator; - TBMIterateResult *matchResult; + + /* + * If blockno is InvalidBlockNumber, all of the other fields in the + * matchResult are meaningless. + */ + TBMIterateResult matchResult; OffsetNumber matchOffsets[TBM_MAX_TUPLES_PER_PAGE]; int matchNtuples; diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h index e185635c10b..99f795ceab5 100644 --- a/src/include/nodes/tidbitmap.h +++ b/src/include/nodes/tidbitmap.h @@ -101,8 +101,8 @@ extern bool tbm_is_empty(const TIDBitmap *tbm); extern TBMPrivateIterator *tbm_begin_private_iterate(TIDBitmap *tbm); extern dsa_pointer tbm_prepare_shared_iterate(TIDBitmap *tbm); -extern TBMIterateResult *tbm_private_iterate(TBMPrivateIterator *iterator); -extern TBMIterateResult *tbm_shared_iterate(TBMSharedIterator *iterator); +extern bool tbm_private_iterate(TBMPrivateIterator *iterator, TBMIterateResult *tbmres); +extern bool tbm_shared_iterate(TBMSharedIterator *iterator, TBMIterateResult *tbmres); extern void tbm_end_private_iterate(TBMPrivateIterator *iterator); extern void tbm_end_shared_iterate(TBMSharedIterator *iterator); extern TBMSharedIterator *tbm_attach_shared_iterate(dsa_area *dsa, @@ -113,7 +113,7 @@ extern TBMIterator tbm_begin_iterate(TIDBitmap *tbm, dsa_area *dsa, dsa_pointer dsp); extern void tbm_end_iterate(TBMIterator *iterator); -extern TBMIterateResult *tbm_iterate(TBMIterator *iterator); +extern bool tbm_iterate(TBMIterator *iterator, TBMIterateResult *tbmres); static inline bool tbm_exhausted(TBMIterator *iterator) -- 2.34.1
From e0f329e09c12dc24902f0562e91f93e19dbee4fe Mon Sep 17 00:00:00 2001 From: Melanie Plageman <melanieplage...@gmail.com> Date: Fri, 21 Feb 2025 15:32:33 -0500 Subject: [PATCH v34 3/3] Remove table AM callback scan_bitmap_next_block After pushing the bitmap iterator into table-AM specific code (as part of making bitmap heap scan use the read stream API), scan_bitmap_next_block() no longer returns the current block number. Since scan_bitmap_next_block() isn't returning any relevant information to bitmap table scan code, it makes more sense to get rid of it. Now, bitmap table scan code only calls table_scan_bitmap_next_tuple(), and the heap AM implementation of scan_bitmap_next_block() is a local helper in heapam_handler.c. Reviewed-by: Tomas Vondra <to...@vondra.me> Discussion: https://postgr.es/m/d4bb26c9-fe07-439e-ac53-c0e244387e01%40vondra.me --- src/backend/access/heap/heapam_handler.c | 372 ++++++++++++---------- src/backend/access/table/tableamapi.c | 3 - src/backend/executor/nodeBitmapHeapscan.c | 73 ++--- src/backend/optimizer/util/plancat.c | 2 +- src/include/access/tableam.h | 90 ++---- 5 files changed, 244 insertions(+), 296 deletions(-) diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c index 0f7dd79f28e..c4f5d7307b4 100644 --- a/src/backend/access/heap/heapam_handler.c +++ b/src/backend/access/heap/heapam_handler.c @@ -56,6 +56,10 @@ static bool SampleHeapTupleVisible(TableScanDesc scan, Buffer buffer, static BlockNumber heapam_scan_get_blocks_done(HeapScanDesc hscan); +static bool BitmapHeapScanNextBlock(TableScanDesc scan, + bool *recheck, + uint64 *lossy_pages, uint64 *exact_pages); + /* ------------------------------------------------------------------------ * Slot related callbacks for heap AM @@ -2116,198 +2120,44 @@ heapam_estimate_rel_size(Relation rel, int32 *attr_widths, */ static bool -heapam_scan_bitmap_next_block(TableScanDesc scan, +heapam_scan_bitmap_next_tuple(TableScanDesc scan, + TupleTableSlot *slot, bool *recheck, - uint64 *lossy_pages, uint64 *exact_pages) + uint64 *lossy_pages, + uint64 *exact_pages) { BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan; HeapScanDesc hscan = (HeapScanDesc) bscan; - BlockNumber block; - void *per_buffer_data; - Buffer buffer; - Snapshot snapshot; - int ntup; - TBMIterateResult *tbmres; - OffsetNumber offsets[TBM_MAX_TUPLES_PER_PAGE]; - int noffsets = -1; - - Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN); - Assert(hscan->rs_read_stream); - - hscan->rs_cindex = 0; - hscan->rs_ntuples = 0; - - /* Release buffer containing previous block. */ - if (BufferIsValid(hscan->rs_cbuf)) - { - ReleaseBuffer(hscan->rs_cbuf); - hscan->rs_cbuf = InvalidBuffer; - } - - hscan->rs_cbuf = read_stream_next_buffer(hscan->rs_read_stream, - &per_buffer_data); - - if (BufferIsInvalid(hscan->rs_cbuf)) - { - if (BufferIsValid(bscan->rs_vmbuffer)) - { - ReleaseBuffer(bscan->rs_vmbuffer); - bscan->rs_vmbuffer = InvalidBuffer; - } - - /* - * Bitmap is exhausted. Time to emit empty tuples if relevant. We emit - * all empty tuples at the end instead of emitting them per block we - * skip fetching. This is necessary because the streaming read API - * will only return TBMIterateResults for blocks actually fetched. - * When we skip fetching a block, we keep track of how many empty - * tuples to emit at the end of the BitmapHeapScan. We do not recheck - * all NULL tuples. - */ - *recheck = false; - return bscan->rs_empty_tuples_pending > 0; - } - - Assert(per_buffer_data); - - tbmres = per_buffer_data; - - Assert(BlockNumberIsValid(tbmres->blockno)); - Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno); - - /* Exact pages need their tuple offsets extracted. */ - if (!tbmres->lossy) - noffsets = tbm_extract_page_tuple(tbmres, offsets, - TBM_MAX_TUPLES_PER_PAGE); - - *recheck = tbmres->recheck; - - block = hscan->rs_cblock = tbmres->blockno; - buffer = hscan->rs_cbuf; - snapshot = scan->rs_snapshot; - - ntup = 0; - - /* - * Prune and repair fragmentation for the whole page, if possible. - */ - heap_page_prune_opt(scan->rs_rd, buffer); - - /* - * We must hold share lock on the buffer content while examining tuple - * visibility. Afterwards, however, the tuples we have found to be - * visible are guaranteed good as long as we hold the buffer pin. - */ - LockBuffer(buffer, BUFFER_LOCK_SHARE); + OffsetNumber targoffset; + Page page; + ItemId lp; /* - * We need two separate strategies for lossy and non-lossy cases. + * Out of range? If so, nothing more to look at on this page */ - if (!tbmres->lossy) - { - /* - * Bitmap is non-lossy, so we just look through the offsets listed in - * tbmres; but we have to follow any HOT chain starting at each such - * offset. - */ - int curslot; - - /* We must have extracted the tuple offsets by now */ - Assert(noffsets > -1); - - for (curslot = 0; curslot < noffsets; curslot++) - { - OffsetNumber offnum = offsets[curslot]; - ItemPointerData tid; - HeapTupleData heapTuple; - - ItemPointerSet(&tid, block, offnum); - if (heap_hot_search_buffer(&tid, scan->rs_rd, buffer, snapshot, - &heapTuple, NULL, true)) - hscan->rs_vistuples[ntup++] = ItemPointerGetOffsetNumber(&tid); - } - } - else + while (hscan->rs_cindex >= hscan->rs_ntuples) { /* - * Bitmap is lossy, so we must examine each line pointer on the page. - * But we can ignore HOT chains, since we'll check each tuple anyway. + * Emit empty tuples before advancing to the next block */ - Page page = BufferGetPage(buffer); - OffsetNumber maxoff = PageGetMaxOffsetNumber(page); - OffsetNumber offnum; - - for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum)) + if (bscan->rs_empty_tuples_pending > 0) { - ItemId lp; - HeapTupleData loctup; - bool valid; - - lp = PageGetItemId(page, offnum); - if (!ItemIdIsNormal(lp)) - continue; - loctup.t_data = (HeapTupleHeader) PageGetItem(page, lp); - loctup.t_len = ItemIdGetLength(lp); - loctup.t_tableOid = scan->rs_rd->rd_id; - ItemPointerSet(&loctup.t_self, block, offnum); - valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer); - if (valid) - { - hscan->rs_vistuples[ntup++] = offnum; - PredicateLockTID(scan->rs_rd, &loctup.t_self, snapshot, - HeapTupleHeaderGetXmin(loctup.t_data)); - } - HeapCheckForSerializableConflictOut(valid, scan->rs_rd, &loctup, - buffer, snapshot); + /* + * If we don't have to fetch the tuple, just return nulls. + */ + ExecStoreAllNullTuple(slot); + bscan->rs_empty_tuples_pending--; + return true; } - } - LockBuffer(buffer, BUFFER_LOCK_UNLOCK); - - Assert(ntup <= MaxHeapTuplesPerPage); - hscan->rs_ntuples = ntup; - - if (tbmres->lossy) - (*lossy_pages)++; - else - (*exact_pages)++; - - /* - * Return true to indicate that a valid block was found and the bitmap is - * not exhausted. If there are no visible tuples on this page, - * hscan->rs_ntuples will be 0 and heapam_scan_bitmap_next_tuple() will - * return false returning control to this function to advance to the next - * block in the bitmap. - */ - return true; -} - -static bool -heapam_scan_bitmap_next_tuple(TableScanDesc scan, - TupleTableSlot *slot) -{ - BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan; - HeapScanDesc hscan = (HeapScanDesc) bscan; - OffsetNumber targoffset; - Page page; - ItemId lp; - - if (bscan->rs_empty_tuples_pending > 0) - { /* - * If we don't have to fetch the tuple, just return nulls. + * Returns false if the bitmap is exhausted and there are no further + * blocks we need to scan. */ - ExecStoreAllNullTuple(slot); - bscan->rs_empty_tuples_pending--; - return true; + if (!BitmapHeapScanNextBlock(scan, recheck, lossy_pages, exact_pages)) + return false; } - /* - * Out of range? If so, nothing more to look at on this page - */ - if (hscan->rs_cindex >= hscan->rs_ntuples) - return false; - targoffset = hscan->rs_vistuples[hscan->rs_cindex]; page = BufferGetPage(hscan->rs_cbuf); lp = PageGetItemId(page, targoffset); @@ -2614,6 +2464,177 @@ SampleHeapTupleVisible(TableScanDesc scan, Buffer buffer, } } +/* + * Helper function get the next block of a bitmap heap scan. Returns true when + * it got the next block and saved it in the scan descriptor and false when + * the bitmap and or relation are exhausted. + */ +static bool +BitmapHeapScanNextBlock(TableScanDesc scan, + bool *recheck, + uint64 *lossy_pages, uint64 *exact_pages) +{ + BitmapHeapScanDesc bscan = (BitmapHeapScanDesc) scan; + HeapScanDesc hscan = (HeapScanDesc) bscan; + BlockNumber block; + void *per_buffer_data; + Buffer buffer; + Snapshot snapshot; + int ntup; + TBMIterateResult *tbmres; + OffsetNumber offsets[TBM_MAX_TUPLES_PER_PAGE]; + int noffsets = -1; + + Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN); + Assert(hscan->rs_read_stream); + + hscan->rs_cindex = 0; + hscan->rs_ntuples = 0; + + /* Release buffer containing previous block. */ + if (BufferIsValid(hscan->rs_cbuf)) + { + ReleaseBuffer(hscan->rs_cbuf); + hscan->rs_cbuf = InvalidBuffer; + } + + hscan->rs_cbuf = read_stream_next_buffer(hscan->rs_read_stream, + &per_buffer_data); + + if (BufferIsInvalid(hscan->rs_cbuf)) + { + if (BufferIsValid(bscan->rs_vmbuffer)) + { + ReleaseBuffer(bscan->rs_vmbuffer); + bscan->rs_vmbuffer = InvalidBuffer; + } + + /* + * Bitmap is exhausted. Time to emit empty tuples if relevant. We emit + * all empty tuples at the end instead of emitting them per block we + * skip fetching. This is necessary because the streaming read API + * will only return TBMIterateResults for blocks actually fetched. + * When we skip fetching a block, we keep track of how many empty + * tuples to emit at the end of the BitmapHeapScan. We do not recheck + * all NULL tuples. + */ + *recheck = false; + return bscan->rs_empty_tuples_pending > 0; + } + + Assert(per_buffer_data); + + tbmres = per_buffer_data; + + Assert(BlockNumberIsValid(tbmres->blockno)); + Assert(BufferGetBlockNumber(hscan->rs_cbuf) == tbmres->blockno); + + /* Exact pages need their tuple offsets extracted. */ + if (!tbmres->lossy) + noffsets = tbm_extract_page_tuple(tbmres, offsets, + TBM_MAX_TUPLES_PER_PAGE); + + *recheck = tbmres->recheck; + + block = hscan->rs_cblock = tbmres->blockno; + buffer = hscan->rs_cbuf; + snapshot = scan->rs_snapshot; + + ntup = 0; + + /* + * Prune and repair fragmentation for the whole page, if possible. + */ + heap_page_prune_opt(scan->rs_rd, buffer); + + /* + * We must hold share lock on the buffer content while examining tuple + * visibility. Afterwards, however, the tuples we have found to be + * visible are guaranteed good as long as we hold the buffer pin. + */ + LockBuffer(buffer, BUFFER_LOCK_SHARE); + + /* + * We need two separate strategies for lossy and non-lossy cases. + */ + if (!tbmres->lossy) + { + /* + * Bitmap is non-lossy, so we just look through the offsets listed in + * tbmres; but we have to follow any HOT chain starting at each such + * offset. + */ + int curslot; + + /* We must have extracted the tuple offsets by now */ + Assert(noffsets > -1); + + for (curslot = 0; curslot < noffsets; curslot++) + { + OffsetNumber offnum = offsets[curslot]; + ItemPointerData tid; + HeapTupleData heapTuple; + + ItemPointerSet(&tid, block, offnum); + if (heap_hot_search_buffer(&tid, scan->rs_rd, buffer, snapshot, + &heapTuple, NULL, true)) + hscan->rs_vistuples[ntup++] = ItemPointerGetOffsetNumber(&tid); + } + } + else + { + /* + * Bitmap is lossy, so we must examine each line pointer on the page. + * But we can ignore HOT chains, since we'll check each tuple anyway. + */ + Page page = BufferGetPage(buffer); + OffsetNumber maxoff = PageGetMaxOffsetNumber(page); + OffsetNumber offnum; + + for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum)) + { + ItemId lp; + HeapTupleData loctup; + bool valid; + + lp = PageGetItemId(page, offnum); + if (!ItemIdIsNormal(lp)) + continue; + loctup.t_data = (HeapTupleHeader) PageGetItem(page, lp); + loctup.t_len = ItemIdGetLength(lp); + loctup.t_tableOid = scan->rs_rd->rd_id; + ItemPointerSet(&loctup.t_self, block, offnum); + valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer); + if (valid) + { + hscan->rs_vistuples[ntup++] = offnum; + PredicateLockTID(scan->rs_rd, &loctup.t_self, snapshot, + HeapTupleHeaderGetXmin(loctup.t_data)); + } + HeapCheckForSerializableConflictOut(valid, scan->rs_rd, &loctup, + buffer, snapshot); + } + } + + LockBuffer(buffer, BUFFER_LOCK_UNLOCK); + + Assert(ntup <= MaxHeapTuplesPerPage); + hscan->rs_ntuples = ntup; + + if (tbmres->lossy) + (*lossy_pages)++; + else + (*exact_pages)++; + + /* + * Return true to indicate that a valid block was found and the bitmap is + * not exhausted. If there are no visible tuples on this page, + * hscan->rs_ntuples will be 0 and heapam_scan_bitmap_next_tuple() will + * return false returning control to this function to advance to the next + * block in the bitmap. + */ + return true; +} /* ------------------------------------------------------------------------ * Definition of the heap table access method. @@ -2673,7 +2694,6 @@ static const TableAmRoutine heapam_methods = { .relation_estimate_size = heapam_estimate_rel_size, - .scan_bitmap_next_block = heapam_scan_bitmap_next_block, .scan_bitmap_next_tuple = heapam_scan_bitmap_next_tuple, .scan_sample_next_block = heapam_scan_sample_next_block, .scan_sample_next_tuple = heapam_scan_sample_next_tuple diff --git a/src/backend/access/table/tableamapi.c b/src/backend/access/table/tableamapi.c index 760a36fd2a1..476663b66aa 100644 --- a/src/backend/access/table/tableamapi.c +++ b/src/backend/access/table/tableamapi.c @@ -91,9 +91,6 @@ GetTableAmRoutine(Oid amhandler) Assert(routine->relation_estimate_size != NULL); - /* optional, but one callback implies presence of the other */ - Assert((routine->scan_bitmap_next_block == NULL) == - (routine->scan_bitmap_next_tuple == NULL)); Assert(routine->scan_sample_next_block != NULL); Assert(routine->scan_sample_next_tuple != NULL); diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c index 6df34094a13..3e33360c0fc 100644 --- a/src/backend/executor/nodeBitmapHeapscan.c +++ b/src/backend/executor/nodeBitmapHeapscan.c @@ -138,69 +138,44 @@ BitmapTableScanSetup(BitmapHeapScanState *node) static TupleTableSlot * BitmapHeapNext(BitmapHeapScanState *node) { - ExprContext *econtext; - TableScanDesc scan; - TupleTableSlot *slot; - - /* - * extract necessary information from index scan node - */ - econtext = node->ss.ps.ps_ExprContext; - slot = node->ss.ss_ScanTupleSlot; - scan = node->ss.ss_currentScanDesc; + ExprContext *econtext = node->ss.ps.ps_ExprContext; + TupleTableSlot *slot = node->ss.ss_ScanTupleSlot; /* * If we haven't yet performed the underlying index scan, do it, and begin * the iteration over the bitmap. */ if (!node->initialized) - { BitmapTableScanSetup(node); - scan = node->ss.ss_currentScanDesc; - goto new_page; - } - for (;;) + while (table_scan_bitmap_next_tuple(node->ss.ss_currentScanDesc, + slot, &node->recheck, + &node->stats.lossy_pages, + &node->stats.exact_pages)) { - while (table_scan_bitmap_next_tuple(scan, slot)) - { - /* - * Continuing in previously obtained page. - */ - - CHECK_FOR_INTERRUPTS(); + /* + * Continuing in previously obtained page. + */ + CHECK_FOR_INTERRUPTS(); - /* - * If we are using lossy info, we have to recheck the qual - * conditions at every tuple. - */ - if (node->recheck) + /* + * If we are using lossy info, we have to recheck the qual conditions + * at every tuple. + */ + if (node->recheck) + { + econtext->ecxt_scantuple = slot; + if (!ExecQualAndReset(node->bitmapqualorig, econtext)) { - econtext->ecxt_scantuple = slot; - if (!ExecQualAndReset(node->bitmapqualorig, econtext)) - { - /* Fails recheck, so drop it and loop back for another */ - InstrCountFiltered2(node, 1); - ExecClearTuple(slot); - continue; - } + /* Fails recheck, so drop it and loop back for another */ + InstrCountFiltered2(node, 1); + ExecClearTuple(slot); + continue; } - - /* OK to return this tuple */ - return slot; } -new_page: - - /* - * Returns false if the bitmap is exhausted and there are no further - * blocks we need to scan. - */ - if (!table_scan_bitmap_next_block(scan, - &node->recheck, - &node->stats.lossy_pages, - &node->stats.exact_pages)) - break; + /* OK to return this tuple */ + return slot; } /* diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c index 71abb01f655..0489ad36644 100644 --- a/src/backend/optimizer/util/plancat.c +++ b/src/backend/optimizer/util/plancat.c @@ -325,7 +325,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent, info->amcanparallel = amroutine->amcanparallel; info->amhasgettuple = (amroutine->amgettuple != NULL); info->amhasgetbitmap = amroutine->amgetbitmap != NULL && - relation->rd_tableam->scan_bitmap_next_block != NULL; + relation->rd_tableam->scan_bitmap_next_tuple != NULL; info->amcanmarkpos = (amroutine->ammarkpos != NULL && amroutine->amrestrpos != NULL); info->amcostestimate = amroutine->amcostestimate; diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h index 507d4ebe68f..b8cb1e744ad 100644 --- a/src/include/access/tableam.h +++ b/src/include/access/tableam.h @@ -780,43 +780,23 @@ typedef struct TableAmRoutine */ /* - * Prepare to fetch / check / return tuples from `blockno` as part of a - * bitmap table scan. `scan` was started via table_beginscan_bm(). Return - * false if the bitmap is exhausted and true otherwise. - * - * This will typically read and pin the target block, and do the necessary - * work to allow scan_bitmap_next_tuple() to return tuples (e.g. it might - * make sense to perform tuple visibility checks at this time). - * - * `lossy_pages` and `exact_pages` are EXPLAIN counters that can be - * incremented by the table AM to indicate whether or not the block's - * representation in the bitmap is lossy. + * Fetch the next tuple of a bitmap table scan into `slot` and return true + * if a visible tuple was found, false otherwise. * - * `recheck` is set by the table AM to indicate whether or not the tuples - * from this block should be rechecked. Tuples from lossy pages will - * always need to be rechecked, but some non-lossy pages' tuples may also - * require recheck. + * `lossy_pages` is incremented if the bitmap is lossy for the selected + * page; otherwise, `exact_pages` is incremented. These are tracked for + * display in EXPLAIN ANALYZE output. * * Prefetching additional data from the bitmap is left to the table AM. * - * Optional callback, but either both scan_bitmap_next_block and - * scan_bitmap_next_tuple need to exist, or neither. + * This is an optional callback. */ - bool (*scan_bitmap_next_block) (TableScanDesc scan, + bool (*scan_bitmap_next_tuple) (TableScanDesc scan, + TupleTableSlot *slot, bool *recheck, uint64 *lossy_pages, uint64 *exact_pages); - /* - * Fetch the next tuple of a bitmap table scan into `slot` and return true - * if a visible tuple was found, false otherwise. - * - * Optional callback, but either both scan_bitmap_next_block and - * scan_bitmap_next_tuple need to exist, or neither. - */ - bool (*scan_bitmap_next_tuple) (TableScanDesc scan, - TupleTableSlot *slot); - /* * Prepare to fetch tuples from the next block in a sample scan. Return * false if the sample scan is finished, true otherwise. `scan` was @@ -1939,51 +1919,24 @@ table_relation_estimate_size(Relation rel, int32 *attr_widths, */ /* - * Prepare to fetch / check / return tuples as part of a bitmap table scan. - * `scan` needs to have been started via table_beginscan_bm(). Returns false - * if there are no more blocks in the bitmap, true otherwise. - * - * `lossy_pages` and `exact_pages` are EXPLAIN counters that can be - * incremented by the table AM to indicate whether or not the block's - * representation in the bitmap is lossy. + * Fetch / check / return tuples as part of a bitmap table scan. `scan` needs + * to have been started via table_beginscan_bm(). Fetch the next tuple of a + * bitmap table scan into `slot` and return true if a visible tuple was found, + * false otherwise. * - * `recheck` is set by the table AM to indicate whether or not the tuples - * from this block should be rechecked. + * `recheck` is set by the table AM to indicate whether or not the tuple in + * `slot` should be rechecked. Tuples from lossy pages will always need to be + * rechecked, but some non-lossy pages' tuples may also require recheck. * - * Note, this is an optionally implemented function, therefore should only be - * used after verifying the presence (at plan time or such). + * `lossy_pages` is incremented if the block's representation in the bitmap is + * lossy; otherwise, `exact_pages` is incremented. */ static inline bool -table_scan_bitmap_next_block(TableScanDesc scan, +table_scan_bitmap_next_tuple(TableScanDesc scan, + TupleTableSlot *slot, bool *recheck, uint64 *lossy_pages, uint64 *exact_pages) -{ - /* - * We don't expect direct calls to table_scan_bitmap_next_block with valid - * CheckXidAlive for catalog or regular tables. See detailed comments in - * xact.c where these variables are declared. - */ - if (unlikely(TransactionIdIsValid(CheckXidAlive) && !bsysscan)) - elog(ERROR, "unexpected table_scan_bitmap_next_block call during logical decoding"); - - return scan->rs_rd->rd_tableam->scan_bitmap_next_block(scan, - recheck, - lossy_pages, - exact_pages); -} - -/* - * Fetch the next tuple of a bitmap table scan into `slot` and return true if - * a visible tuple was found, false otherwise. - * table_scan_bitmap_next_block() needs to previously have selected a - * block (i.e. returned true), and no previous - * table_scan_bitmap_next_tuple() for the same block may have - * returned false. - */ -static inline bool -table_scan_bitmap_next_tuple(TableScanDesc scan, - TupleTableSlot *slot) { /* * We don't expect direct calls to table_scan_bitmap_next_tuple with valid @@ -1994,7 +1947,10 @@ table_scan_bitmap_next_tuple(TableScanDesc scan, elog(ERROR, "unexpected table_scan_bitmap_next_tuple call during logical decoding"); return scan->rs_rd->rd_tableam->scan_bitmap_next_tuple(scan, - slot); + slot, + recheck, + lossy_pages, + exact_pages); } /* -- 2.34.1
