protected static List generateRanges()

in dbeam-core/src/main/java/com/spotify/dbeam/args/ParallelQueryBuilder.java [145:174]

• 18 lines of code
• 4 McCabe index (conditional complexity)

  protected static List<QueryRange> generateRanges(
      final long min, final long max, final int parallelism) {
    // We try not to generate more than queryParallelism. Hence we don't want to loose number by
    // rounding down. Also when queryParallelism is higher than max - min, we don't want 0 ranges
    long bucketSize = (long) Math.ceil((double) (max - min) / (double) parallelism);
    bucketSize = bucketSize == 0 ? 1 : bucketSize; // If max and min is same, we export only 1 query
    final List<QueryRange> ranges = new ArrayList<>(parallelism);

    long i = min;
    while (i + bucketSize < max) {
      // Include lower bound and exclude the upper bound.
      ranges.add(new QueryRange(i, i + bucketSize, true));
      i = i + bucketSize;
    }

    // Add last query
    if (i + bucketSize >= max) {
      // If bucket size exceeds max, we must use max and the predicate
      // should include upper bound.
      ranges.add(new QueryRange(i, max, false));
    }

    // If queryParallelism is higher than max-min, this will generate less ranges.
    // But lets never generate more ranges.
    checkState(
        ranges.size() <= parallelism,
        "Unable to generate expected number of ranges for given min max.");

    return ranges;
  }