github.com/apache/arrow/go/v14@v14.0.1/arrow/example_test.go

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package arrow_test

import (
	"fmt"
	"log"

	"github.com/apache/arrow/go/v14/arrow"
	"github.com/apache/arrow/go/v14/arrow/array"
	"github.com/apache/arrow/go/v14/arrow/memory"
	"github.com/apache/arrow/go/v14/arrow/tensor"
)

// This example demonstrates how to build an array of int64 values using a builder and Append.
// Whilst convenient for small arrays,
func Example_minimal() {
	// Create an allocator.
	pool := memory.NewGoAllocator()

	// Create an int64 array builder.
	builder := array.NewInt64Builder(pool)
	defer builder.Release()

	builder.Append(1)
	builder.Append(2)
	builder.Append(3)
	builder.AppendNull()
	builder.Append(5)
	builder.Append(6)
	builder.Append(7)
	builder.Append(8)

	// Finish building the int64 array and reset the builder.
	ints := builder.NewInt64Array()
	defer ints.Release()

	// Enumerate the values.
	for i, v := range ints.Int64Values() {
		fmt.Printf("ints[%d] = ", i)
		if ints.IsNull(i) {
			fmt.Println(array.NullValueStr)
		} else {
			fmt.Println(v)
		}
	}
	fmt.Printf("ints = %v\n", ints)

	// Output:
	// ints[0] = 1
	// ints[1] = 2
	// ints[2] = 3
	// ints[3] = (null)
	// ints[4] = 5
	// ints[5] = 6
	// ints[6] = 7
	// ints[7] = 8
	// ints = [1 2 3 (null) 5 6 7 8]
}

// This example demonstrates creating an array, sourcing the values and
// null bitmaps directly from byte slices. The null count is set to
// UnknownNullCount, instructing the array to calculate the
// null count from the bitmap when NullN is called.
func Example_fromMemory() {
	// create LSB packed bits with the following pattern:
	// 01010011 11000101
	data := memory.NewBufferBytes([]byte{0xca, 0xa3})

	// create LSB packed validity (null) bitmap, where every 4th element is null:
	// 11101110 11101110
	nullBitmap := memory.NewBufferBytes([]byte{0x77, 0x77})

	// Create a boolean array and lazily determine NullN using UnknownNullCount
	bools := array.NewBoolean(16, data, nullBitmap, array.UnknownNullCount)
	defer bools.Release()

	// Show the null count
	fmt.Printf("NullN()  = %d\n", bools.NullN())

	// Enumerate the values.
	n := bools.Len()
	for i := 0; i < n; i++ {
		fmt.Printf("bools[%d] = ", i)
		if bools.IsNull(i) {
			fmt.Println(array.NullValueStr)
		} else {
			fmt.Printf("%t\n", bools.Value(i))
		}
	}

	// Output:
	// NullN()  = 4
	// bools[0] = false
	// bools[1] = true
	// bools[2] = false
	// bools[3] = (null)
	// bools[4] = false
	// bools[5] = false
	// bools[6] = true
	// bools[7] = (null)
	// bools[8] = true
	// bools[9] = true
	// bools[10] = false
	// bools[11] = (null)
	// bools[12] = false
	// bools[13] = true
	// bools[14] = false
	// bools[15] = (null)
}

// This example shows how to create a List array.
// The resulting array should be:
//
//	[[0, 1, 2], [], [3], [4, 5], [6, 7, 8], [], [9]]
func Example_listArray() {
	pool := memory.NewGoAllocator()

	lb := array.NewListBuilder(pool, arrow.PrimitiveTypes.Int64)
	defer lb.Release()

	vb := lb.ValueBuilder().(*array.Int64Builder)
	vb.Reserve(10)

	lb.Append(true)
	vb.Append(0)
	vb.Append(1)
	vb.Append(2)

	lb.AppendNull()

	lb.Append(true)
	vb.Append(3)

	lb.Append(true)
	vb.Append(4)
	vb.Append(5)

	lb.Append(true)
	vb.Append(6)
	vb.Append(7)
	vb.Append(8)

	lb.AppendNull()

	lb.Append(true)
	vb.Append(9)

	arr := lb.NewArray().(*array.List)
	defer arr.Release()

	arr.DataType().(*arrow.ListType).SetElemNullable(false)
	fmt.Printf("NullN()   = %d\n", arr.NullN())
	fmt.Printf("Len()     = %d\n", arr.Len())
	fmt.Printf("Offsets() = %v\n", arr.Offsets())
	fmt.Printf("Type()    = %v\n", arr.DataType())

	offsets := arr.Offsets()[1:]

	varr := arr.ListValues().(*array.Int64)

	pos := 0
	for i := 0; i < arr.Len(); i++ {
		if !arr.IsValid(i) {
			fmt.Printf("List[%d]   = (null)\n", i)
			continue
		}
		fmt.Printf("List[%d]   = [", i)
		for j := pos; j < int(offsets[i]); j++ {
			if j != pos {
				fmt.Printf(", ")
			}
			fmt.Printf("%v", varr.Value(j))
		}
		pos = int(offsets[i])
		fmt.Printf("]\n")
	}
	fmt.Printf("List      = %v\n", arr)

	// Output:
	// NullN()   = 2
	// Len()     = 7
	// Offsets() = [0 3 3 4 6 9 9 10]
	// Type()    = list<item: int64>
	// List[0]   = [0, 1, 2]
	// List[1]   = (null)
	// List[2]   = [3]
	// List[3]   = [4, 5]
	// List[4]   = [6, 7, 8]
	// List[5]   = (null)
	// List[6]   = [9]
	// List      = [[0 1 2] (null) [3] [4 5] [6 7 8] (null) [9]]
}

// This example shows how to create a FixedSizeList array.
// The resulting array should be:
//
//	[[0, 1, 2], (null), [3, 4, 5], [6, 7, 8], (null)]
func Example_fixedSizeListArray() {
	pool := memory.NewGoAllocator()

	lb := array.NewFixedSizeListBuilder(pool, 3, arrow.PrimitiveTypes.Int64)
	defer lb.Release()

	vb := lb.ValueBuilder().(*array.Int64Builder)
	vb.Reserve(10)

	lb.Append(true)
	vb.Append(0)
	vb.Append(1)
	vb.Append(2)

	lb.AppendNull()

	lb.Append(true)
	vb.Append(3)
	vb.Append(4)
	vb.Append(5)

	lb.Append(true)
	vb.Append(6)
	vb.Append(7)
	vb.Append(8)

	lb.AppendNull()

	arr := lb.NewArray().(*array.FixedSizeList)
	arr.DataType().(*arrow.FixedSizeListType).SetElemNullable(false)
	defer arr.Release()

	fmt.Printf("NullN()   = %d\n", arr.NullN())
	fmt.Printf("Len()     = %d\n", arr.Len())
	fmt.Printf("Type()    = %v\n", arr.DataType())
	fmt.Printf("List      = %v\n", arr)

	// Output:
	// NullN()   = 2
	// Len()     = 5
	// Type()    = fixed_size_list<item: int64>[3]
	// List      = [[0 1 2] (null) [3 4 5] [6 7 8] (null)]
}

// This example shows how to create a Struct array.
// The resulting array should be:
//
//	[{‘joe’, 1}, {null, 2}, null, {‘mark’, 4}]
func Example_structArray() {
	pool := memory.NewGoAllocator()

	dtype := arrow.StructOf([]arrow.Field{
		{Name: "f1", Type: arrow.ListOf(arrow.PrimitiveTypes.Uint8)},
		{Name: "f2", Type: arrow.PrimitiveTypes.Int32},
	}...)

	sb := array.NewStructBuilder(pool, dtype)
	defer sb.Release()

	f1b := sb.FieldBuilder(0).(*array.ListBuilder)
	f1vb := f1b.ValueBuilder().(*array.Uint8Builder)
	f2b := sb.FieldBuilder(1).(*array.Int32Builder)

	sb.Reserve(4)
	f1vb.Reserve(7)
	f2b.Reserve(3)

	sb.Append(true)
	f1b.Append(true)
	f1vb.AppendValues([]byte("joe"), nil)
	f2b.Append(1)

	sb.Append(true)
	f1b.AppendNull()
	f2b.Append(2)

	sb.AppendNull()

	sb.Append(true)
	f1b.Append(true)
	f1vb.AppendValues([]byte("mark"), nil)
	f2b.Append(4)

	arr := sb.NewArray().(*array.Struct)
	defer arr.Release()

	fmt.Printf("NullN() = %d\n", arr.NullN())
	fmt.Printf("Len()   = %d\n", arr.Len())
	fmt.Printf("Type()    = %v\n", arr.DataType())

	list := arr.Field(0).(*array.List)
	offsets := list.Offsets()

	varr := list.ListValues().(*array.Uint8)
	ints := arr.Field(1).(*array.Int32)

	for i := 0; i < arr.Len(); i++ {
		if !arr.IsValid(i) {
			fmt.Printf("Struct[%d] = (null)\n", i)
			continue
		}
		fmt.Printf("Struct[%d] = [", i)
		pos := int(offsets[i])
		switch {
		case list.IsValid(pos):
			fmt.Printf("[")
			for j := offsets[i]; j < offsets[i+1]; j++ {
				if j != offsets[i] {
					fmt.Printf(", ")
				}
				fmt.Printf("%v", string(varr.Value(int(j))))
			}
			fmt.Printf("], ")
		default:
			fmt.Printf("(null), ")
		}
		fmt.Printf("%d]\n", ints.Value(i))
	}

	// Output:
	// NullN() = 1
	// Len()   = 4
	// Type()    = struct<f1: list<item: uint8, nullable>, f2: int32>
	// Struct[0] = [[j, o, e], 1]
	// Struct[1] = [[], 2]
	// Struct[2] = (null)
	// Struct[3] = [[m, a, r, k], 4]
}

// This example shows how one can slice an array.
// The initial (float64) array is:
//
//	[1, 2, 3, (null), 4, 5]
//
// and the sub-slice is:
//
//	[3, (null), 4]
func Example_float64Slice() {
	pool := memory.NewGoAllocator()

	b := array.NewFloat64Builder(pool)
	defer b.Release()

	b.AppendValues(
		[]float64{1, 2, 3, -1, 4, 5},
		[]bool{true, true, true, false, true, true},
	)

	arr := b.NewFloat64Array()
	defer arr.Release()

	fmt.Printf("array = %v\n", arr)

	sli := array.NewSlice(arr, 2, 5).(*array.Float64)
	defer sli.Release()

	fmt.Printf("slice = %v\n", sli)

	// Output:
	// array = [1 2 3 (null) 4 5]
	// slice = [3 (null) 4]
}

func Example_float64Tensor2x5() {
	pool := memory.NewGoAllocator()

	b := array.NewFloat64Builder(pool)
	defer b.Release()

	raw := []float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
	b.AppendValues(raw, nil)

	arr := b.NewFloat64Array()
	defer arr.Release()

	f64 := tensor.NewFloat64(arr.Data(), []int64{2, 5}, nil, []string{"x", "y"})
	defer f64.Release()

	for _, i := range [][]int64{
		{0, 0},
		{0, 1},
		{0, 2},
		{0, 3},
		{0, 4},
		{1, 0},
		{1, 1},
		{1, 2},
		{1, 3},
		{1, 4},
	} {
		fmt.Printf("arr%v = %v\n", i, f64.Value(i))
	}

	// Output:
	// arr[0 0] = 1
	// arr[0 1] = 2
	// arr[0 2] = 3
	// arr[0 3] = 4
	// arr[0 4] = 5
	// arr[1 0] = 6
	// arr[1 1] = 7
	// arr[1 2] = 8
	// arr[1 3] = 9
	// arr[1 4] = 10
}

func Example_float64Tensor2x5ColMajor() {
	pool := memory.NewGoAllocator()

	b := array.NewFloat64Builder(pool)
	defer b.Release()

	raw := []float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
	b.AppendValues(raw, nil)

	arr := b.NewFloat64Array()
	defer arr.Release()

	f64 := tensor.NewFloat64(arr.Data(), []int64{2, 5}, []int64{8, 16}, []string{"x", "y"})
	defer f64.Release()

	for _, i := range [][]int64{
		{0, 0},
		{0, 1},
		{0, 2},
		{0, 3},
		{0, 4},
		{1, 0},
		{1, 1},
		{1, 2},
		{1, 3},
		{1, 4},
	} {
		fmt.Printf("arr%v = %v\n", i, f64.Value(i))
	}

	// Output:
	// arr[0 0] = 1
	// arr[0 1] = 3
	// arr[0 2] = 5
	// arr[0 3] = 7
	// arr[0 4] = 9
	// arr[1 0] = 2
	// arr[1 1] = 4
	// arr[1 2] = 6
	// arr[1 3] = 8
	// arr[1 4] = 10
}

func Example_record() {
	pool := memory.NewGoAllocator()

	schema := arrow.NewSchema(
		[]arrow.Field{
			{Name: "f1-i32", Type: arrow.PrimitiveTypes.Int32},
			{Name: "f2-f64", Type: arrow.PrimitiveTypes.Float64},
		},
		nil,
	)

	b := array.NewRecordBuilder(pool, schema)
	defer b.Release()

	b.Field(0).(*array.Int32Builder).AppendValues([]int32{1, 2, 3, 4, 5, 6}, nil)
	b.Field(0).(*array.Int32Builder).AppendValues([]int32{7, 8, 9, 10}, []bool{true, true, false, true})
	b.Field(1).(*array.Float64Builder).AppendValues([]float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, nil)

	rec := b.NewRecord()
	defer rec.Release()

	for i, col := range rec.Columns() {
		fmt.Printf("column[%d] %q: %v\n", i, rec.ColumnName(i), col)
	}

	// Output:
	// column[0] "f1-i32": [1 2 3 4 5 6 7 8 (null) 10]
	// column[1] "f2-f64": [1 2 3 4 5 6 7 8 9 10]
}

func Example_recordReader() {
	pool := memory.NewGoAllocator()

	schema := arrow.NewSchema(
		[]arrow.Field{
			{Name: "f1-i32", Type: arrow.PrimitiveTypes.Int32},
			{Name: "f2-f64", Type: arrow.PrimitiveTypes.Float64},
		},
		nil,
	)

	b := array.NewRecordBuilder(pool, schema)
	defer b.Release()

	b.Field(0).(*array.Int32Builder).AppendValues([]int32{1, 2, 3, 4, 5, 6}, nil)
	b.Field(0).(*array.Int32Builder).AppendValues([]int32{7, 8, 9, 10}, []bool{true, true, false, true})
	b.Field(1).(*array.Float64Builder).AppendValues([]float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, nil)

	rec1 := b.NewRecord()
	defer rec1.Release()

	b.Field(0).(*array.Int32Builder).AppendValues([]int32{11, 12, 13, 14, 15, 16, 17, 18, 19, 20}, nil)
	b.Field(1).(*array.Float64Builder).AppendValues([]float64{11, 12, 13, 14, 15, 16, 17, 18, 19, 20}, nil)

	rec2 := b.NewRecord()
	defer rec2.Release()

	itr, err := array.NewRecordReader(schema, []arrow.Record{rec1, rec2})
	if err != nil {
		log.Fatal(err)
	}
	defer itr.Release()

	n := 0
	for itr.Next() {
		rec := itr.Record()
		for i, col := range rec.Columns() {
			fmt.Printf("rec[%d][%q]: %v\n", n, rec.ColumnName(i), col)
		}
		n++
	}

	// Output:
	// rec[0]["f1-i32"]: [1 2 3 4 5 6 7 8 (null) 10]
	// rec[0]["f2-f64"]: [1 2 3 4 5 6 7 8 9 10]
	// rec[1]["f1-i32"]: [11 12 13 14 15 16 17 18 19 20]
	// rec[1]["f2-f64"]: [11 12 13 14 15 16 17 18 19 20]
}

func Example_table() {
	pool := memory.NewGoAllocator()

	schema := arrow.NewSchema(
		[]arrow.Field{
			{Name: "f1-i32", Type: arrow.PrimitiveTypes.Int32},
			{Name: "f2-f64", Type: arrow.PrimitiveTypes.Float64},
		},
		nil,
	)

	b := array.NewRecordBuilder(pool, schema)
	defer b.Release()

	b.Field(0).(*array.Int32Builder).AppendValues([]int32{1, 2, 3, 4, 5, 6}, nil)
	b.Field(0).(*array.Int32Builder).AppendValues([]int32{7, 8, 9, 10}, []bool{true, true, false, true})
	b.Field(1).(*array.Float64Builder).AppendValues([]float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, nil)

	rec1 := b.NewRecord()
	defer rec1.Release()

	b.Field(0).(*array.Int32Builder).AppendValues([]int32{11, 12, 13, 14, 15, 16, 17, 18, 19, 20}, nil)
	b.Field(1).(*array.Float64Builder).AppendValues([]float64{11, 12, 13, 14, 15, 16, 17, 18, 19, 20}, nil)

	rec2 := b.NewRecord()
	defer rec2.Release()

	tbl := array.NewTableFromRecords(schema, []arrow.Record{rec1, rec2})
	defer tbl.Release()

	tr := array.NewTableReader(tbl, 5)
	defer tr.Release()

	n := 0
	for tr.Next() {
		rec := tr.Record()
		for i, col := range rec.Columns() {
			fmt.Printf("rec[%d][%q]: %v\n", n, rec.ColumnName(i), col)
		}
		n++
	}

	// Output:
	// rec[0]["f1-i32"]: [1 2 3 4 5]
	// rec[0]["f2-f64"]: [1 2 3 4 5]
	// rec[1]["f1-i32"]: [6 7 8 (null) 10]
	// rec[1]["f2-f64"]: [6 7 8 9 10]
	// rec[2]["f1-i32"]: [11 12 13 14 15]
	// rec[2]["f2-f64"]: [11 12 13 14 15]
	// rec[3]["f1-i32"]: [16 17 18 19 20]
	// rec[3]["f2-f64"]: [16 17 18 19 20]
}

// This example demonstrates how to create a Map Array.
// The resulting array should be:
//
//	[{["ab" "cd" "ef" "gh"] [1 2 3 4]} (null) {["ab" "cd" "ef" "gh"] [(null) 2 5 1]}]
func Example_mapArray() {
	pool := memory.NewGoAllocator()
	mb := array.NewMapBuilder(pool, arrow.BinaryTypes.String, arrow.PrimitiveTypes.Int16, false)
	defer mb.Release()

	kb := mb.KeyBuilder().(*array.StringBuilder)
	ib := mb.ItemBuilder().(*array.Int16Builder)

	keys := []string{"ab", "cd", "ef", "gh"}

	mb.Append(true)
	kb.AppendValues(keys, nil)
	ib.AppendValues([]int16{1, 2, 3, 4}, nil)

	mb.AppendNull()

	mb.Append(true)
	kb.AppendValues(keys, nil)
	ib.AppendValues([]int16{-1, 2, 5, 1}, []bool{false, true, true, true})

	arr := mb.NewMapArray()
	defer arr.Release()

	fmt.Printf("NullN() = %d\n", arr.NullN())
	fmt.Printf("Len()   = %d\n", arr.Len())

	offsets := arr.Offsets()
	keyArr := arr.Keys().(*array.String)
	itemArr := arr.Items().(*array.Int16)

	for i := 0; i < arr.Len(); i++ {
		if arr.IsNull(i) {
			fmt.Printf("Map[%d] = (null)\n", i)
			continue
		}

		fmt.Printf("Map[%d] = {", i)
		for j := offsets[i]; j < offsets[i+1]; j++ {
			if j != offsets[i] {
				fmt.Printf(", ")
			}
			fmt.Printf("%v => ", keyArr.Value(int(j)))
			if itemArr.IsValid(int(j)) {
				fmt.Printf("%v", itemArr.Value(int(j)))
			} else {
				fmt.Printf(array.NullValueStr)
			}
		}
		fmt.Printf("}\n")
	}
	fmt.Printf("Map    = %v\n", arr)

	// Output:
	// NullN() = 1
	// Len()   = 3
	// Map[0] = {ab => 1, cd => 2, ef => 3, gh => 4}
	// Map[1] = (null)
	// Map[2] = {ab => (null), cd => 2, ef => 5, gh => 1}
	// Map    = [{["ab" "cd" "ef" "gh"] [1 2 3 4]} (null) {["ab" "cd" "ef" "gh"] [(null) 2 5 1]}]
}

func Example_sparseUnionArray() {
	pool := memory.NewGoAllocator()

	sparseBuilder := array.NewEmptySparseUnionBuilder(pool)
	defer sparseBuilder.Release()

	i8Builder := array.NewInt8Builder(pool)
	defer i8Builder.Release()
	i8Code := sparseBuilder.AppendChild(i8Builder, "i8")

	strBuilder := array.NewStringBuilder(pool)
	defer strBuilder.Release()
	strCode := sparseBuilder.AppendChild(strBuilder, "str")

	f64Builder := array.NewFloat64Builder(pool)
	defer f64Builder.Release()
	f64Code := sparseBuilder.AppendChild(f64Builder, "f64")

	values := []interface{}{int8(33), "abc", float64(1.0), float64(-1.0), nil,
		"", int8(10), "def", int8(-10), float64(0.5)}

	for _, v := range values {
		switch v := v.(type) {
		case int8:
			sparseBuilder.Append(i8Code)
			i8Builder.Append(v)
			strBuilder.AppendEmptyValue()
			f64Builder.AppendEmptyValue()
		case string:
			sparseBuilder.Append(strCode)
			i8Builder.AppendEmptyValue()
			strBuilder.Append(v)
			f64Builder.AppendEmptyValue()
		case float64:
			sparseBuilder.Append(f64Code)
			i8Builder.AppendEmptyValue()
			strBuilder.AppendEmptyValue()
			f64Builder.Append(v)
		case nil:
			sparseBuilder.AppendNull()
		}
	}

	arr := sparseBuilder.NewSparseUnionArray()
	defer arr.Release()

	fmt.Printf("Len() = %d\n", arr.Len())
	fields := arr.UnionType().Fields()
	for i := 0; i < arr.Len(); i++ {
		child := arr.ChildID(i)
		data := arr.Field(child)
		field := fields[child]

		if data.IsNull(i) {
			fmt.Printf("[%d]   = (null)\n", i)
			continue
		}
		var v interface{}
		switch varr := data.(type) {
		case *array.Int8:
			v = varr.Value(i)
		case *array.String:
			v = varr.Value(i)
		case *array.Float64:
			v = varr.Value(i)
		}
		fmt.Printf("[%d]   = %#5v {%s}\n", i, v, field.Name)
	}

	fmt.Printf("i8:  %s\n", arr.Field(0))
	fmt.Printf("str: %s\n", arr.Field(1))
	fmt.Printf("f64: %s\n", arr.Field(2))

	// Output:
	// Len() = 10
	// [0]   =    33 {i8}
	// [1]   = "abc" {str}
	// [2]   =     1 {f64}
	// [3]   =    -1 {f64}
	// [4]   = (null)
	// [5]   =    "" {str}
	// [6]   =    10 {i8}
	// [7]   = "def" {str}
	// [8]   =   -10 {i8}
	// [9]   =   0.5 {f64}
	// i8:  [33 0 0 0 (null) 0 10 0 -10 0]
	// str: ["" "abc" "" "" "" "" "" "def" "" ""]
	// f64: [0 0 1 -1 0 0 0 0 0 0.5]
}

func Example_denseUnionArray() {
	pool := memory.NewGoAllocator()

	denseBuilder := array.NewEmptyDenseUnionBuilder(pool)
	defer denseBuilder.Release()

	i8Builder := array.NewInt8Builder(pool)
	defer i8Builder.Release()
	i8Code := denseBuilder.AppendChild(i8Builder, "i8")

	strBuilder := array.NewStringBuilder(pool)
	defer strBuilder.Release()
	strCode := denseBuilder.AppendChild(strBuilder, "str")

	f64Builder := array.NewFloat64Builder(pool)
	defer f64Builder.Release()
	f64Code := denseBuilder.AppendChild(f64Builder, "f64")

	values := []interface{}{int8(33), "abc", float64(1.0), float64(-1.0), nil,
		"", int8(10), "def", int8(-10), float64(0.5)}

	for _, v := range values {
		switch v := v.(type) {
		case int8:
			denseBuilder.Append(i8Code)
			i8Builder.Append(v)
		case string:
			denseBuilder.Append(strCode)
			strBuilder.Append(v)
		case float64:
			denseBuilder.Append(f64Code)
			f64Builder.Append(v)
		case nil:
			denseBuilder.AppendNull()
		}
	}

	arr := denseBuilder.NewDenseUnionArray()
	defer arr.Release()

	fmt.Printf("Len() = %d\n", arr.Len())
	fields := arr.UnionType().Fields()
	offsets := arr.RawValueOffsets()
	for i := 0; i < arr.Len(); i++ {
		child := arr.ChildID(i)
		data := arr.Field(child)
		field := fields[child]

		idx := int(offsets[i])
		if data.IsNull(idx) {
			fmt.Printf("[%d]   = (null)\n", i)
			continue
		}
		var v interface{}
		switch varr := data.(type) {
		case *array.Int8:
			v = varr.Value(idx)
		case *array.String:
			v = varr.Value(idx)
		case *array.Float64:
			v = varr.Value(idx)
		}
		fmt.Printf("[%d]   = %#5v {%s}\n", i, v, field.Name)
	}

	fmt.Printf("i8:  %s\n", arr.Field(0))
	fmt.Printf("str: %s\n", arr.Field(1))
	fmt.Printf("f64: %s\n", arr.Field(2))

	// Output:
	// Len() = 10
	// [0]   =    33 {i8}
	// [1]   = "abc" {str}
	// [2]   =     1 {f64}
	// [3]   =    -1 {f64}
	// [4]   = (null)
	// [5]   =    "" {str}
	// [6]   =    10 {i8}
	// [7]   = "def" {str}
	// [8]   =   -10 {i8}
	// [9]   =   0.5 {f64}
	// i8:  [33 (null) 10 -10]
	// str: ["abc" "" "def"]
	// f64: [1 -1 0.5]
}