From f607a4b9994e622d2c5f15054dce24f2f99ca255 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Tue, 21 Jan 2025 17:36:50 -0500 Subject: [PATCH v27 1/5] Move BitmapTableScan per-scan setup into a helper Add BitmapTableScanSetup(), a helper which contains all of the code that must be done on every scan of the table in a bitmap table scan. This includes scanning the index, building the bitmap, and setting up the scan descriptors. Much of BitmapHeapNext() code was this setup, so it made sense to put it in a helper function. --- src/backend/executor/nodeBitmapHeapscan.c | 203 +++++++++++----------- 1 file changed, 104 insertions(+), 99 deletions(-) diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c index be616683f98..7b1fd24b419 100644 --- a/src/backend/executor/nodeBitmapHeapscan.c +++ b/src/backend/executor/nodeBitmapHeapscan.c @@ -48,6 +48,7 @@ #include "utils/rel.h" #include "utils/spccache.h" +static void BitmapTableScanSetup(BitmapHeapScanState *node); static TupleTableSlot *BitmapHeapNext(BitmapHeapScanState *node); static inline void BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate); static inline void BitmapAdjustPrefetchIterator(BitmapHeapScanState *node); @@ -57,6 +58,107 @@ static inline void BitmapPrefetch(BitmapHeapScanState *node, 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) +{ + TBMIterator tbmiterator = {0}; + ParallelBitmapHeapState *pstate = node->pstate; + dsa_area *dsa = node->ss.ps.state->es_query_dsa; + + if (!pstate) + { + node->tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node)); + + if (!node->tbm || !IsA(node->tbm, TIDBitmap)) + elog(ERROR, "unrecognized result from subplan"); + } + else if (BitmapShouldInitializeSharedState(pstate)) + { + /* + * The leader will immediately come out of the function, but others + * will be blocked until leader populates the TBM and wakes them up. + */ + node->tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node)); + if (!node->tbm || !IsA(node->tbm, TIDBitmap)) + elog(ERROR, "unrecognized result from subplan"); + + /* + * Prepare to iterate over the TBM. This will return the dsa_pointer + * of the iterator state which will be used by multiple processes to + * iterate jointly. + */ + 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); + } + + tbmiterator = tbm_begin_iterate(node->tbm, dsa, + pstate ? + 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. + */ + if (!node->ss.ss_currentScanDesc) + { + bool need_tuples = false; + + /* + * 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. + */ + need_tuples = (node->ss.ps.plan->qual != NIL || + node->ss.ps.plan->targetlist != NIL); + + node->ss.ss_currentScanDesc = + table_beginscan_bm(node->ss.ss_currentRelation, + node->ss.ps.state->es_snapshot, + 0, + NULL, + need_tuples); + } + + node->ss.ss_currentScanDesc->st.rs_tbmiterator = tbmiterator; + node->initialized = true; +} + + /* ---------------------------------------------------------------- * BitmapHeapNext * @@ -68,10 +170,8 @@ BitmapHeapNext(BitmapHeapScanState *node) { ExprContext *econtext; TableScanDesc scan; - TIDBitmap *tbm; TupleTableSlot *slot; ParallelBitmapHeapState *pstate = node->pstate; - dsa_area *dsa = node->ss.ps.state->es_query_dsa; /* * extract necessary information from index scan node @@ -79,110 +179,15 @@ BitmapHeapNext(BitmapHeapScanState *node) econtext = node->ss.ps.ps_ExprContext; slot = node->ss.ss_ScanTupleSlot; scan = node->ss.ss_currentScanDesc; - tbm = node->tbm; /* * If we haven't yet performed the underlying index scan, do it, and begin * the iteration over the bitmap. - * - * 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. */ if (!node->initialized) { - TBMIterator tbmiterator; - - if (!pstate) - { - tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node)); - - if (!tbm || !IsA(tbm, TIDBitmap)) - elog(ERROR, "unrecognized result from subplan"); - - node->tbm = tbm; - } - else if (BitmapShouldInitializeSharedState(pstate)) - { - /* - * The leader will immediately come out of the function, but - * others will be blocked until leader populates the TBM and wakes - * them up. - */ - tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node)); - if (!tbm || !IsA(tbm, TIDBitmap)) - elog(ERROR, "unrecognized result from subplan"); - - node->tbm = tbm; - - /* - * Prepare to iterate over the TBM. This will return the - * dsa_pointer of the iterator state which will be used by - * multiple processes to iterate jointly. - */ - pstate->tbmiterator = tbm_prepare_shared_iterate(tbm); - -#ifdef USE_PREFETCH - if (node->prefetch_maximum > 0) - { - pstate->prefetch_iterator = - tbm_prepare_shared_iterate(tbm); - } -#endif /* USE_PREFETCH */ - - /* We have initialized the shared state so wake up others. */ - BitmapDoneInitializingSharedState(pstate); - } - - tbmiterator = tbm_begin_iterate(tbm, dsa, - pstate ? - pstate->tbmiterator : - InvalidDsaPointer); - -#ifdef USE_PREFETCH - if (node->prefetch_maximum > 0) - node->prefetch_iterator = - tbm_begin_iterate(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. - */ - if (!scan) - { - bool need_tuples = false; - - /* - * 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. - */ - need_tuples = (node->ss.ps.plan->qual != NIL || - node->ss.ps.plan->targetlist != NIL); - - scan = table_beginscan_bm(node->ss.ss_currentRelation, - node->ss.ps.state->es_snapshot, - 0, - NULL, - need_tuples); - - node->ss.ss_currentScanDesc = scan; - } - - scan->st.rs_tbmiterator = tbmiterator; - node->initialized = true; - + BitmapTableScanSetup(node); + scan = node->ss.ss_currentScanDesc; goto new_page; } -- 2.45.2