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tableam: Avoid relying on relation size to determine validity of tids.

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Instead add a tableam callback to do so. To avoid adding per
validation overhead, pass a scan to tuple_tid_valid. In heap's case
we'd otherwise incurred a RelationGetNumberOfBlocks() call for each
tid - which'd have added noticable overhead to nodeTidscan.c.

Author: Andres Freund
Reviewed-By: Ashwin Agrawal
Discussion: https://postgr.es/m/20190515185447.gno2jtqxyktylyvs@alap3.anarazel.de
This commit is contained in:
Andres Freund
2019-05-17 18:52:01 -07:00
parent 7f44ede594
commit 147e3722f7
7 changed files with 129 additions and 57 deletions
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10
src/backend/access/heap/heapam_handler.c
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@ -204,6 +204,15 @@ heapam_fetch_row_version(Relation relation,
return false;
}
static bool
heapam_tuple_tid_valid(TableScanDesc scan, ItemPointer tid)
{
HeapScanDesc hscan = (HeapScanDesc) scan;
return ItemPointerIsValid(tid) &&
ItemPointerGetBlockNumber(tid) < hscan->rs_nblocks;
}
static bool
heapam_tuple_satisfies_snapshot(Relation rel, TupleTableSlot *slot,
Snapshot snapshot)
@ -2568,6 +2577,7 @@ static const TableAmRoutine heapam_methods = {
.tuple_fetch_row_version = heapam_fetch_row_version,
.tuple_get_latest_tid = heap_get_latest_tid,
.tuple_tid_valid = heapam_tuple_tid_valid,
.tuple_satisfies_snapshot = heapam_tuple_satisfies_snapshot,
.compute_xid_horizon_for_tuples = heap_compute_xid_horizon_for_tuples,