BitmapHeapScan: Push skip_fetch optimization into table AM
Commit 7c70996ebf0949b142 introduced an optimization to allow bitmap
scans to operate like index-only scans by not fetching a block from the
heap if none of the underlying data is needed and the block is marked
all visible in the visibility map.
With the introduction of table AMs, a FIXME was added to this code
indicating that the skip_fetch logic should be pushed into the table
AM-specific code, as not all table AMs may use a visibility map in the
same way.
This commit resolves this FIXME for the current block. The layering
violation is still present in BitmapHeapScans's prefetching code, which
uses the visibility map to decide whether or not to prefetch a block.
However, this can be addressed independently.
Author: Melanie Plageman
Reviewed-by: Andres Freund, Heikki Linnakangas, Tomas Vondra, Mark Dilger
Discussion: https://postgr.es/m/CAAKRu_ZwCwWFeL_H3ia26bP2e7HiKLWt0ZmGXPVwPO6uXq0vaA%40mail.gmail.com
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/04e72ed617be354a53a076b76c6644e364ed80a3
Modified Files
--------------
src/backend/access/heap/heapam.c | 15 ++++
src/backend/access/heap/heapam_handler.c | 29 +++++++
src/backend/executor/nodeBitmapHeapscan.c | 124 ++++++++++--------------------
src/include/access/heapam.h | 10 +++
src/include/access/tableam.h | 12 ++-
src/include/nodes/execnodes.h | 8 +-
6 files changed, 105 insertions(+), 93 deletions(-)