public void setDistributionBitCount(int distributionBitCount,
                                            ProgressToken progress)
        {
            // Setting distribution bits for explicit bucket source is essentially
            // a no-op, since its buckets already are fixed at 32 used bits.
            progress.setDistributionBitCount(distributionBitCount);
            this.distributionBitCount = distributionBitCount;
            if (log.isLoggable(Level.FINE)) {
                log.log(Level.FINE, "Set distribution bit count to "
                        + distributionBitCount + " for explicit bucket source (no-op)");
            }
        }
Provides an explicit set of bucket IDs to iterate over. Will immediately
set these as pending in the {@link ProgressToken}, as it is presumed this set is
rather small. Changing the distribution bit count for this source is
effectively a no-op, as explicit bucket IDs should not be implicitly
changed.
documentapi/src/main/java/com/yahoo/documentapi/VisitorIterator.java