public synchronized void setNumBucketBits(int numBucketBits) {
        if (numBucketBits == this.numBucketBits) {
            return;
        }
        this.numBucketBits = numBucketBits;
        bucketToColumn = new int[getNumBuckets(numBucketBits)];
        int numColumns = this.numColumns;
        reset();
        setNumColumns(numColumns);
    }
Sets the number of buckets to use for this document distribution object. This will reset and setup this object
from scratch. The original number of columns is maintained.

@param numBucketBits The new number of bits to use for bucket id.
document/src/main/java/com/yahoo/document/BucketDistribution.java