TieredMergePolicy中的为什么当hitTooLarge为true时，skew设为最优值

// Roughly measure "skew" of the merge, i.e. how

    // "balanced" the merge is (whether the segments are

    // about the same size), which can range from

    // 1.0/numSegsBeingMerged (good) to 1.0 (poor). Heavily

    // lopsided merges (skew near 1.0) is no good; it means

    // O(N^2) merge cost over time:

    final double skew;

    if (hitTooLarge) {

      // Pretend the merge has perfect skew; skew doesn't

      // matter in this case because this merge will not

      // "cascade" and so it cannot lead to N^2 merge cost

      // over time:

      final int mergeFactor = (int) Math.min(maxMergeAtOnce, segsPerTier);

      skew = 1.0 / mergeFactor; 

    } else {

      skew =

          ((double) floorSize(segmentsSizes.get(candidate.get(0)).sizeInBytes))

              / totAfterMergeBytesFloored; 

    }