Thread: pgsql: Remove HeapBitmapScan's skip_fetch optimization
Remove HeapBitmapScan's skip_fetch optimization The optimization does not take the removal of TIDs by a concurrent vacuum into account. The concurrent vacuum can remove dead TIDs and make pages ALL_VISIBLE while those dead TIDs are referenced in the bitmap. This can lead to a skip_fetch scan returning too many tuples. It likely would be possible to implement this optimization safely, but we don't have the necessary infrastructure in place. Nor is it clear that it's worth building that infrastructure, given how limited the skip_fetch optimization is. In the backbranches we just disable the optimization by always passing need_tuples=true to table_beginscan_bm(). We can't perform API/ABI changes in the backbranches and we want to make the change as minimal as possible. Author: Matthias van de Meent <boekewurm+postgres@gmail.com> Reported-By: Konstantin Knizhnik <knizhnik@garret.ru> Discussion: https://postgr.es/m/CAEze2Wg3gXXZTr6_rwC+s4-o2ZVFB5F985uUSgJTsECx6AmGcQ@mail.gmail.com Backpatch-through: 13 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/459e7bf8e2f8ab894dc613fa8555b74c4eef6969 Modified Files -------------- src/backend/access/heap/heapam.c | 61 ++++--------------------------- src/backend/access/heap/heapam_handler.c | 46 +---------------------- src/backend/executor/nodeBitmapHeapscan.c | 15 +------- src/include/access/heapam.h | 12 +----- src/include/access/tableam.h | 12 +----- 5 files changed, 13 insertions(+), 133 deletions(-)