@Override
        public long count(final String childStreamType) throws IOException {
            final InputStream data = getChildInputStream(childStreamType);
            final InputStream boundaryIndex = getChildInputStream(InternalStreamTypeNames.BOUNDARY_INDEX);

            try (final SegmentInputStream segmentInputStream = new RASegmentInputStream(data, boundaryIndex)) {
                return segmentInputStream.count();
            }
        }
Gets the output stream for this stream target.
stroom-data/stroom-data-store-mock/src/main/java/stroom/data/store/mock/MockStore.java