VectorizedOrcAcidRowBatchReader will not be used for original files. This will likely look like a perf regression when converting a table from non-acid to acid until it runs through a major compaction.
With Load Data support, if large files are added via Load Data, the read ops will not vectorize until major compaction.
There is no reason why this should be the case. Just like OrcRawRecordMerger, VectorizedOrcAcidRowBatchReader can look at the other files in the logical tranche/bucket and calculate the offset for the RowBatch of the split. (Presumably getRecordReader().getRowNumber() works the same in vector mode).
In this case we don't even need OrcSplit.isOriginal() - the reader can infer it from file path... which in particular simplifies OrcInputFormat.determineSplitStrategies()