From 222baec639676912407a1c5dd81f0aea07cc5352 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Wed, 30 Nov 2022 17:06:43 -0500 Subject: [PATCH v4 2/6] Add heapgettup_initial_page() helper --- src/backend/access/heap/heapam.c | 215 ++++++++++++------------------- 1 file changed, 82 insertions(+), 133 deletions(-) diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index 36f14a0a9e..37795eab67 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -523,6 +523,58 @@ heapgettup_no_movement(HeapScanDesc scan) return; } +static inline BlockNumber +heapgettup_initial_page(HeapScanDesc scan, ScanDirection dir) +{ + Assert(!ScanDirectionIsNoMovement(dir)); + Assert(!scan->rs_inited); + + /* return null immediately if relation is empty */ + if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0) + return InvalidBlockNumber; + + scan->rs_inited = true; + + /* forward and serial */ + if (ScanDirectionIsForward(dir) && scan->rs_base.rs_parallel == NULL) + return scan->rs_startblock; + + /* forward and parallel */ + if (ScanDirectionIsForward(dir)) + { + table_block_parallelscan_startblock_init(scan->rs_base.rs_rd, + scan->rs_parallelworkerdata, + (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel); + + return table_block_parallelscan_nextpage(scan->rs_base.rs_rd, + scan->rs_parallelworkerdata, + (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel); + } + + /* backward parallel scan not supported */ + Assert(scan->rs_base.rs_parallel == NULL); + + /* + * Disable reporting to syncscan logic in a backwards scan; it's + * not very likely anyone else is doing the same thing at the same + * time, and much more likely that we'll just bollix things for + * forward scanners. + */ + scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC; + + /* + * Start from last page of the scan. Ensure we take into account + * rs_numblocks if it's been adjusted by heap_setscanlimits(). + */ + if (scan->rs_numblocks != InvalidBlockNumber) + return (scan->rs_startblock + scan->rs_numblocks - 1) % scan->rs_nblocks; + + if (scan->rs_startblock > 0) + return scan->rs_startblock - 1; + + return scan->rs_nblocks - 1; +} + /* ---------------- * heapgettup - fetch next heap tuple * @@ -569,48 +621,20 @@ heapgettup(HeapScanDesc scan, return; } - /* - * calculate next starting lineoff, given scan direction - */ if (ScanDirectionIsForward(dir)) { if (!scan->rs_inited) { - /* - * return null immediately if relation is empty - */ - if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0) + block = heapgettup_initial_page(scan, dir); + + if (block == InvalidBlockNumber) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } - if (scan->rs_base.rs_parallel != NULL) - { - ParallelBlockTableScanDesc pbscan = - (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel; - ParallelBlockTableScanWorker pbscanwork = - scan->rs_parallelworkerdata; - - table_block_parallelscan_startblock_init(scan->rs_base.rs_rd, - pbscanwork, pbscan); - - block = table_block_parallelscan_nextpage(scan->rs_base.rs_rd, - pbscanwork, pbscan); - - /* Other processes might have already finished the scan. */ - if (block == InvalidBlockNumber) - { - Assert(!BufferIsValid(scan->rs_cbuf)); - tuple->t_data = NULL; - return; - } - } - else - block = scan->rs_startblock; /* first page */ heapgetpage((TableScanDesc) scan, block); - lineoff = FirstOffsetNumber; /* first offnum */ - scan->rs_inited = true; + lineoff = FirstOffsetNumber; } else { @@ -632,60 +656,36 @@ heapgettup(HeapScanDesc scan, else { Assert(backward); - /* backward parallel scan not supported */ - Assert(scan->rs_base.rs_parallel == NULL); if (!scan->rs_inited) { - /* - * return null immediately if relation is empty - */ - if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0) + block = heapgettup_initial_page(scan, dir); + + if (block == InvalidBlockNumber) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } - /* - * Disable reporting to syncscan logic in a backwards scan; it's - * not very likely anyone else is doing the same thing at the same - * time, and much more likely that we'll just bollix things for - * forward scanners. - */ - scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC; - - /* - * Start from last page of the scan. Ensure we take into account - * rs_numblocks if it's been adjusted by heap_setscanlimits(). - */ - if (scan->rs_numblocks != InvalidBlockNumber) - block = (scan->rs_startblock + scan->rs_numblocks - 1) % scan->rs_nblocks; - else if (scan->rs_startblock > 0) - block = scan->rs_startblock - 1; - else - block = scan->rs_nblocks - 1; heapgetpage((TableScanDesc) scan, block); + LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); + + page = BufferGetPage(scan->rs_cbuf); + TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, page); + lines = PageGetMaxOffsetNumber(page); + lineoff = lines; /* final offnum */ } else { /* continue from previously returned page/tuple */ block = scan->rs_cblock; /* current page */ - } - - LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); + LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); - page = BufferGetPage(scan->rs_cbuf); - TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, page); - lines = PageGetMaxOffsetNumber(page); + page = BufferGetPage(scan->rs_cbuf); + TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, page); + lines = PageGetMaxOffsetNumber(page); - if (!scan->rs_inited) - { - lineoff = lines; /* final offnum */ - scan->rs_inited = true; - } - else - { /* * The previous returned tuple may have been vacuumed since the * previous scan when we use a non-MVCC snapshot, so we must @@ -893,41 +893,17 @@ heapgettup_pagemode(HeapScanDesc scan, { if (!scan->rs_inited) { - /* - * return null immediately if relation is empty - */ - if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0) + block = heapgettup_initial_page(scan, dir); + + if (block == InvalidBlockNumber) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } - if (scan->rs_base.rs_parallel != NULL) - { - ParallelBlockTableScanDesc pbscan = - (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel; - ParallelBlockTableScanWorker pbscanwork = - scan->rs_parallelworkerdata; - - table_block_parallelscan_startblock_init(scan->rs_base.rs_rd, - pbscanwork, pbscan); - - block = table_block_parallelscan_nextpage(scan->rs_base.rs_rd, - pbscanwork, pbscan); - /* Other processes might have already finished the scan. */ - if (block == InvalidBlockNumber) - { - Assert(!BufferIsValid(scan->rs_cbuf)); - tuple->t_data = NULL; - return; - } - } - else - block = scan->rs_startblock; /* first page */ heapgetpage((TableScanDesc) scan, block); lineindex = 0; - scan->rs_inited = true; } else { @@ -946,58 +922,31 @@ heapgettup_pagemode(HeapScanDesc scan, else { Assert(backward); - /* backward parallel scan not supported */ - Assert(scan->rs_base.rs_parallel == NULL); if (!scan->rs_inited) { - /* - * return null immediately if relation is empty - */ - if (scan->rs_nblocks == 0 || scan->rs_numblocks == 0) + block = heapgettup_initial_page(scan, dir); + + if (block == InvalidBlockNumber) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } - /* - * Disable reporting to syncscan logic in a backwards scan; it's - * not very likely anyone else is doing the same thing at the same - * time, and much more likely that we'll just bollix things for - * forward scanners. - */ - scan->rs_base.rs_flags &= ~SO_ALLOW_SYNC; - - /* - * Start from last page of the scan. Ensure we take into account - * rs_numblocks if it's been adjusted by heap_setscanlimits(). - */ - if (scan->rs_numblocks != InvalidBlockNumber) - block = (scan->rs_startblock + scan->rs_numblocks - 1) % scan->rs_nblocks; - else if (scan->rs_startblock > 0) - block = scan->rs_startblock - 1; - else - block = scan->rs_nblocks - 1; heapgetpage((TableScanDesc) scan, block); + page = BufferGetPage(scan->rs_cbuf); + TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, page); + lines = scan->rs_ntuples; + lineindex = lines - 1; } else { /* continue from previously returned page/tuple */ block = scan->rs_cblock; /* current page */ - } - - page = BufferGetPage(scan->rs_cbuf); - TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, page); - lines = scan->rs_ntuples; - - if (!scan->rs_inited) - { - lineindex = lines - 1; - scan->rs_inited = true; - } - else - { + page = BufferGetPage(scan->rs_cbuf); + TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, page); + lines = scan->rs_ntuples; lineindex = scan->rs_cindex - 1; } /* block and lineindex now reference the previous visible tid */ -- 2.38.1