From 64db84204c690f279d55f8a66424764b1792ae1a Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Wed, 30 Nov 2022 14:18:08 -0500 Subject: [PATCH v4 4/6] Add heapgettup() helpers Add heapgettup_start_page() and heapgettup_continue_page(), helper functions for heapgettup(). --- src/backend/access/heap/heapam.c | 93 +++++++++++++++++++++----------- 1 file changed, 61 insertions(+), 32 deletions(-) diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index ed1980dffa..e586dda5aa 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -575,6 +575,65 @@ heapgettup_initial_page(HeapScanDesc scan, ScanDirection dir) return scan->rs_nblocks - 1; } +static inline Page +heapgettup_start_page(HeapScanDesc scan, BlockNumber block, ScanDirection dir, + int *linesleft, OffsetNumber *lineoff) +{ + Page page; + + Assert(scan->rs_inited); + Assert(BufferIsValid(scan->rs_cbuf)); + + /* Caller is responsible for ensuring buffer is locked if needed */ + page = BufferGetPage(scan->rs_cbuf); + + TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, page); + + *linesleft = PageGetMaxOffsetNumber((Page) page) - FirstOffsetNumber + 1; + + if (ScanDirectionIsForward(dir)) + *lineoff = FirstOffsetNumber; + else + *lineoff = (OffsetNumber) (*linesleft); + + /* lineoff now references the physically previous or next tid */ + return page; +} + +static inline Page +heapgettup_continue_page(HeapScanDesc scan, BlockNumber block, ScanDirection + dir, int *linesleft, OffsetNumber *lineoff) +{ + Page page; + + Assert(scan->rs_inited); + Assert(BufferIsValid(scan->rs_cbuf)); + + /* Caller is responsible for ensuring buffer is locked if needed */ + page = BufferGetPage(scan->rs_cbuf); + + TestForOldSnapshot(scan->rs_base.rs_snapshot, scan->rs_base.rs_rd, page); + + if (ScanDirectionIsForward(dir)) + { + *lineoff = OffsetNumberNext(scan->rs_cindex); + *linesleft = PageGetMaxOffsetNumber(page) - (*lineoff) + 1; + } + else + { + /* + * The previous returned tuple may have been vacuumed since the + * previous scan when we use a non-MVCC snapshot, so we must + * re-establish the lineoff <= PageGetMaxOffsetNumber(page) + * invariant + */ + *lineoff = Min(PageGetMaxOffsetNumber(page), OffsetNumberPrev(scan->rs_cindex)); + *linesleft = *lineoff; + } + /* block and lineoff now reference the physically next tid */ + return page; +} + /* ---------------- * heapgettup - fetch next heap tuple * @@ -632,45 +691,15 @@ heapgettup(HeapScanDesc scan, } heapgetpage((TableScanDesc) scan, block); - LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); - page = BufferGetPage(scan->rs_cbuf); - TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, page); - - linesleft = PageGetMaxOffsetNumber((Page) page) - FirstOffsetNumber + 1; - - if (ScanDirectionIsForward(dir)) - lineoff = FirstOffsetNumber; - else - lineoff = (OffsetNumber) linesleft; + page = heapgettup_start_page(scan, block, dir, &linesleft, &lineoff); } else { block = scan->rs_cblock; /* current page */ LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); - - page = BufferGetPage(scan->rs_cbuf); - TestForOldSnapshot(snapshot, scan->rs_base.rs_rd, page); - - if (ScanDirectionIsForward(dir)) - { - lineoff = OffsetNumberNext(scan->rs_cindex); - /* block and lineoff now reference the physically next tid */ - linesleft = PageGetMaxOffsetNumber(page) - lineoff + 1; - } - else - { - /* - * The previous returned tuple may have been vacuumed since the - * previous scan when we use a non-MVCC snapshot, so we must - * re-establish the lineoff <= PageGetMaxOffsetNumber(page) - * invariant - */ - lineoff = Min(PageGetMaxOffsetNumber(page), OffsetNumberPrev(scan->rs_cindex)); - /* block and lineoff now reference the physically previous tid */ - linesleft = lineoff; - } + page = heapgettup_continue_page(scan, block, dir, &linesleft, &lineoff); } /* -- 2.38.1