code: func copyOuterRows(innerColOffset, outerColOffset int, src *Chunk, numRows int, dst *Chunk) {
  	if numRows <= 0 {
  		return
  	}
  	row := src.GetRow(0)
  	var srcCols []*column
  	if innerColOffset == 0 {
  		srcCols = src.columns[outerColOffset:]
  	} else {
  		srcCols = src.columns[:innerColOffset]
  	}
  	for i, srcCol := range srcCols {
  		dstCol := dst.columns[outerColOffset+i]
  		dstCol.appendMultiSameNullBitmap(!srcCol.isNull(row.idx), numRows)
  		dstCol.length += numRows
  		if srcCol.isFixed() {
  			elemLen := len(srcCol.elemBuf)
  			start := row.idx * elemLen
  			end := start + numRows*elemLen
  			dstCol.data = append(dstCol.data, srcCol.data[start:end]...)
  		} else {
  			start, end := srcCol.offsets[row.idx], srcCol.offsets[row.idx+numRows]
  			dstCol.data = append(dstCol.data, srcCol.data[start:end]...)
  			offsets := dstCol.offsets
  			elemLen := srcCol.offsets[row.idx+1] - srcCol.offsets[row.idx]
  			for j := 0; j < numRows; j++ {
  				offsets = append(offsets, int32(offsets[len(offsets)-1]+elemLen))
  			}
  			dstCol.offsets = offsets
  		}
  	}
  }
docs: // copyOuterRows copies the continuous 'numRows' outer rows in the source Chunk
  // to the destination Chunk.