code: func BuildColumn(ctx sessionctx.Context, numBuckets, id int64, collector *SampleCollector, tp *types.FieldType) (*Histogram, error) {
  	return BuildColumnHist(ctx, numBuckets, id, collector, tp, collector.Count, collector.FMSketch.NDV(), collector.NullCount)
  }
docs: // BuildColumn builds histogram from samples for column.