Allow on-access pruning to set pages all-visible Many queries do not modify the underlying relation. For such queries, if on-access pruning occurs during the scan, we can check whether the page has become all-visible and update the visibility map accordingly. Previously, only vacuum and COPY FREEZE marked pages as all-visible or all-frozen.
This commit implements on-access VM setting for sequential scans, tid range scans, sample scans, bitmap heap scans, and the underlying heap relation in index scans. Setting the visibility map on-access can avoid write amplification caused by vacuum later needing to set the page all-visible, which could trigger a write and potentially an FPI. It also allows more frequent index-only scans, since they require pages to be marked all-visible in the VM. Author: Melanie Plageman <[email protected]> Reviewed-by: Andres Freund <[email protected]> Reviewed-by: Kirill Reshke <[email protected]> Reviewed-by: Chao Li <[email protected]> Discussion: https://postgr.es/m/flat/CAAKRu_ZMw6Npd_qm2KM%2BFwQ3cMOMx1Dh3VMhp8-V7SOLxdK9-g%40mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/b46e1e54d078def33b840ae1fa6c5236a7b12ec2 Modified Files -------------- src/backend/access/heap/heapam.c | 3 +- src/backend/access/heap/heapam_handler.c | 6 ++- src/backend/access/heap/pruneheap.c | 66 ++++++++++++++++++++++++-------- src/backend/access/heap/vacuumlazy.c | 2 +- src/include/access/heapam.h | 3 +- 5 files changed, 59 insertions(+), 21 deletions(-)
