feat: add support for NewDecimalFromApdDecimal (#119)

expr/decimal_util.go

@@ -17,11 +17,7 @@ var decimalPattern = regexp.MustCompile(`^[+-]?\d*(\.\d*)?([eE][+-]?\d*)?$`)
 // The precision is the total number of digits in the decimal value. The precision is limited to 38 digits.
 // The scale is the number of digits to the right of the decimal point. The scale is limited to the precision.
 func DecimalStringToBytes(decimalStr string) ([16]byte, int32, int32, error) {
-	var (
-		result    [16]byte
-		precision int32
-		scale     int32
-	)
+	var result [16]byte
 
 	strings.Trim(decimalStr, " ")
 	if !decimalPattern.MatchString(decimalStr) {
@@ -34,6 +30,19 @@ func DecimalStringToBytes(decimalStr string) ([16]byte, int32, int32, error) {
 		return result, 0, 0, fmt.Errorf("invalid decimal string %s: %v", decimalStr, err)
 	}
 
+	return DecimalToBytes(dec)
+}
+
+// DecimalToBytes converts apd.Decimal to a 16-byte byte array.
+// 16-byte bytes represents a little-endian 128-bit integer, to be divided by 10^Scale to get the decimal value.
+// This function also returns the precision and scale of the decimal value.
+func DecimalToBytes(dec *apd.Decimal) ([16]byte, int32, int32, error) {
+	var (
+		result    [16]byte
+		precision int32
+		scale     int32
+	)
+
 	if dec.Exponent > 0 {
 		precision = int32(apd.NumDigits(&dec.Coeff)) + dec.Exponent
 		scale = 0
@@ -42,7 +51,7 @@ func DecimalStringToBytes(decimalStr string) ([16]byte, int32, int32, error) {
 		precision = max(int32(apd.NumDigits(&dec.Coeff)), scale+1)
 	}
 	if precision > 38 {
-		return result, precision, scale, fmt.Errorf("number %s exceeds maximum precision of 38 (%d)", decimalStr, precision)
+		return result, precision, scale, fmt.Errorf("number %s exceeds maximum precision of 38 (%d)", dec.String(), precision)
 	}
 
 	coefficient := dec.Coeff

expr/literals.go

@@ -909,6 +909,9 @@ func NewLiteral[T allLiteralTypes](val T, nullable bool) (Literal, error) {
 			},
 		}, nil
 	case *types.Decimal:
+		if len(v.Value) != 16 {
+			return nil, fmt.Errorf("decimal value must be 16 bytes")
+		}
 		return &ProtoLiteral{
 			Value: v.Value,
 			Type: &types.DecimalType{

expr/literals_test.go

@@ -41,6 +41,33 @@ func TestNewDecimalWithType(t *testing.T) {
 	}
 }
 
+func TestNewLiteralWithDecimalBytes(t *testing.T) {
+	tests := []struct {
+		name           string
+		value          []byte
+		precision      int32
+		scale          int32
+		expectedToFail bool
+	}{
+		{"[0]byte", []byte{}, 2, 0, true},
+		{"[2]byte", []byte{0x1, 0x0}, 2, 0, true},
+		{"[3]byte", []byte{0x1, 0x2, 0x0}, 3, 0, true},
+		{"[17]byte", []byte{0x1, 0x0, 0x0, 0x0, 0x5, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, 16, 0, true},
+
+		{"[16]byte", []byte{0x1, 0x0, 0x0, 0x0, 0x5, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, 16, 0, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := expr.NewLiteral[*types.Decimal](&types.Decimal{Value: tt.value, Precision: tt.precision, Scale: tt.scale}, false)
+			if tt.expectedToFail {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
 func TestNewFixedLenWithType(t *testing.T) {
 	tests := []struct {
 		name      string

literal/utils.go

@@ -7,6 +7,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/cockroachdb/apd/v3"
 	"github.com/google/uuid"
 	"github.com/substrait-io/substrait-go/v3/expr"
 	"github.com/substrait-io/substrait-go/v3/proto"
@@ -321,6 +322,14 @@ func NewDecimalFromString(value string) (expr.Literal, error) {
 	return expr.NewLiteral[*types.Decimal](&types.Decimal{Value: v[:16], Precision: precision, Scale: scale}, false)
 }
 
+func NewDecimalFromApdDecimal(value *apd.Decimal, nullable bool) (expr.Literal, error) {
+	v, precision, scale, err := expr.DecimalToBytes(value)
+	if err != nil {
+		return nil, err
+	}
+	return expr.NewLiteral[*types.Decimal](&types.Decimal{Value: v[:16], Precision: precision, Scale: scale}, nullable)
+}
+
 // NewPrecisionTimestampFromTime creates a new PrecisionTimestamp literal from a time.Time timestamp value with given precision.
 func NewPrecisionTimestampFromTime(precision types.TimePrecision, tm time.Time) (expr.Literal, error) {
 	return NewPrecisionTimestamp(precision, types.GetTimeValueByPrecision(tm, precision))

literal/utils_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/cockroachdb/apd/v3"
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -58,22 +59,36 @@ func TestNewDecimalFromString(t *testing.T) {
 	tests := []struct {
 		value   string
 		want    expr.Literal
-		wantErr assert.ErrorAssertionFunc
+		wantErr bool
 	}{
-		{"0", createDecimalLiteral([]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 1, 0, false), assert.NoError},
-		{"111111.222222", createDecimalLiteral([]byte{0xce, 0xb3, 0xbe, 0xde, 0x19, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 12, 6, false), assert.NoError},
-		{"-111111.222222", createDecimalLiteral([]byte{0x32, 0x4c, 0x41, 0x21, 0xe6, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, 12, 6, false), assert.NoError},
-		{"+1", createDecimalLiteral([]byte{0x1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 1, 0, false), assert.NoError},
-		{"-1", createDecimalLiteral([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, 1, 0, false), assert.NoError},
-		{"not a decimal", nil, assert.Error},
+		{"0", createDecimalLiteral([]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 1, 0, false), false},
+		{"111111.222222", createDecimalLiteral([]byte{0xce, 0xb3, 0xbe, 0xde, 0x19, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 12, 6, false), false},
+		{"-111111.222222", createDecimalLiteral([]byte{0x32, 0x4c, 0x41, 0x21, 0xe6, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, 12, 6, false), false},
+		{"+1", createDecimalLiteral([]byte{0x1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 1, 0, false), false},
+		{"-1", createDecimalLiteral([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, 1, 0, false), false},
+		{"not a decimal", nil, true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.value, func(t *testing.T) {
 			got, err := NewDecimalFromString(tt.value)
-			if !tt.wantErr(t, err, fmt.Sprintf("NewDecimalFromString(%v)", tt.value)) {
+			if tt.wantErr {
+				require.Error(t, err, fmt.Sprintf("NewDecimalFromString(%v) expected error", tt.value))
 				return
 			}
+			require.NoError(t, err)
 			assert.Equalf(t, tt.want, got, "NewDecimalFromString(%v)", tt.value)
+
+			dec, _, err := apd.NewFromString(tt.value)
+			require.NoError(t, err)
+			got, err = NewDecimalFromApdDecimal(dec, false)
+			require.NoError(t, err)
+			assert.Equal(t, tt.want, got, "NewDecimalFromApdDecimal(%v)", tt.value)
+
+			got, err = NewDecimalFromApdDecimal(dec, true)
+			require.NoError(t, err)
+			expected, err := protoLiteralWithNullability(tt.want.(*expr.ProtoLiteral), true)
+			require.NoError(t, err)
+			assert.Equal(t, expected, got, "NewDecimalFromApdDecimal(%v)", tt.value)
 		})
 	}
 }
@@ -92,6 +107,17 @@ func createDecimalLiteral(value []byte, precision int32, scale int32, isNullable
 		},
 	}
 }
+
+func protoLiteralWithNullability(lit *expr.ProtoLiteral, nullable bool) (expr.Literal, error) {
+	nullability := proto.Type_NULLABILITY_REQUIRED
+	if nullable {
+		nullability = proto.Type_NULLABILITY_NULLABLE
+	}
+	decType := lit.GetType().WithNullability(nullability)
+
+	return lit.WithType(decType)
+}
+
 func TestNewDecimalFromTwosComplement(t *testing.T) {
 	type args struct {
 		twosComplement []byte