code: @Override
  	public long blocksAccessed() {
  		return Index.searchCost(ii.indexType(), new SearchKeyType(schema(), ii.fieldNames()),
  				tp.recordsOutput(), recordsOutput()) + recordsOutput();
  	}
docs: Estimates the number of block accesses to compute the index selection,
  which is the same as the index traversal cost plus the number of matching
  data records.
  
  @see Plan#blocksAccessed()