the c'tor of VectorizedOrcAcidRowBatchReader has
This is suboptimal since base and deltas are sorted by ROW__ID. So for each split if base we can find min/max ROW_ID and only load events from delta that are in [min,max] range. This will reduce the number of delete events we load in memory (to no more than there in the split).
When we support sorting on PK, the same should apply but we'd need to make sure to store PKs in ORC index
hive.acid.key.index in Orc footer has an index of ROW__IDs so we should know min/max easily for any file written by OrcRecordUpdater