From a74ebc9e51fe210504c63a13220390bbc8b1cef6 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 5 Feb 2022 08:39:53 -0600
Subject: [PATCH] pgtype.Numeric implements Float64Valuer

---
 pgtype/numeric.go      | 55 ++++++++++++++++++++++++------------------
 pgtype/numeric_test.go | 25 +++++++++++++++++++
 2 files changed, 56 insertions(+), 24 deletions(-)

diff --git a/pgtype/numeric.go b/pgtype/numeric.go
index 5bdbd4d5..d2311f3a 100644
--- a/pgtype/numeric.go
+++ b/pgtype/numeric.go
@@ -80,6 +80,35 @@ func (n Numeric) NumericValue() (Numeric, error) {
 	return n, nil
 }
 
+func (n Numeric) Float64Value() (Float8, error) {
+	if !n.Valid {
+		return Float8{}, nil
+	} else if n.NaN {
+		return Float8{Float: math.NaN(), Valid: true}, nil
+	} else if n.InfinityModifier == Infinity {
+		return Float8{Float: math.Inf(1), Valid: true}, nil
+	} else if n.InfinityModifier == NegativeInfinity {
+		return Float8{Float: math.Inf(-1), Valid: true}, nil
+	}
+
+	buf := make([]byte, 0, 32)
+
+	if n.Int == nil {
+		buf = append(buf, '0')
+	} else {
+		buf = append(buf, n.Int.String()...)
+	}
+	buf = append(buf, 'e')
+	buf = append(buf, strconv.FormatInt(int64(n.Exp), 10)...)
+
+	f, err := strconv.ParseFloat(string(buf), 64)
+	if err != nil {
+		return Float8{}, err
+	}
+
+	return Float8{Float: f, Valid: true}, nil
+}
+
 func (n *Numeric) toBigInt() (*big.Int, error) {
 	if n.Exp == 0 {
 		return n.Int, nil
@@ -104,28 +133,6 @@ func (n *Numeric) toBigInt() (*big.Int, error) {
 	return num, nil
 }
 
-func (n *Numeric) toFloat64() (float64, error) {
-	if n.NaN {
-		return math.NaN(), nil
-	} else if n.InfinityModifier == Infinity {
-		return math.Inf(1), nil
-	} else if n.InfinityModifier == NegativeInfinity {
-		return math.Inf(-1), nil
-	}
-
-	buf := make([]byte, 0, 32)
-
-	buf = append(buf, n.Int.String()...)
-	buf = append(buf, 'e')
-	buf = append(buf, strconv.FormatInt(int64(n.Exp), 10)...)
-
-	f, err := strconv.ParseFloat(string(buf), 64)
-	if err != nil {
-		return 0, err
-	}
-	return f, nil
-}
-
 func parseNumericString(str string) (n *big.Int, exp int32, err error) {
 	parts := strings.SplitN(str, ".", 2)
 	digits := strings.Join(parts, "")
@@ -642,12 +649,12 @@ func (scanPlanBinaryNumericToFloat64Scanner) Scan(src []byte, dst interface{}) e
 		return err
 	}
 
-	f64, err := n.toFloat64()
+	f8, err := n.Float64Value()
 	if err != nil {
 		return err
 	}
 
-	return scanner.ScanFloat64(Float8{Float: f64, Valid: true})
+	return scanner.ScanFloat64(f8)
 }
 
 type scanPlanBinaryNumericToInt64Scanner struct{}
diff --git a/pgtype/numeric_test.go b/pgtype/numeric_test.go
index c74fb9a3..0449059e 100644
--- a/pgtype/numeric_test.go
+++ b/pgtype/numeric_test.go
@@ -11,6 +11,7 @@ import (
 
 	"github.com/jackc/pgx/v5/pgtype"
 	"github.com/jackc/pgx/v5/pgtype/testutil"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -117,6 +118,30 @@ func TestNumericCodec(t *testing.T) {
 	})
 }
 
+func TestNumericFloat64Valuer(t *testing.T) {
+	for i, tt := range []struct {
+		n pgtype.Numeric
+		f pgtype.Float8
+	}{
+		{mustParseNumeric(t, "1"), pgtype.Float8{Float: 1, Valid: true}},
+		{mustParseNumeric(t, "0.0000000000000000001"), pgtype.Float8{Float: 0.0000000000000000001, Valid: true}},
+		{mustParseNumeric(t, "-99999999999"), pgtype.Float8{Float: -99999999999, Valid: true}},
+		{pgtype.Numeric{InfinityModifier: pgtype.Infinity, Valid: true}, pgtype.Float8{Float: math.Inf(1), Valid: true}},
+		{pgtype.Numeric{InfinityModifier: pgtype.NegativeInfinity, Valid: true}, pgtype.Float8{Float: math.Inf(-1), Valid: true}},
+		{pgtype.Numeric{Valid: true}, pgtype.Float8{Valid: true}},
+		{pgtype.Numeric{}, pgtype.Float8{}},
+	} {
+		f, err := tt.n.Float64Value()
+		assert.NoErrorf(t, err, "%d", i)
+		assert.Equalf(t, tt.f, f, "%d", i)
+	}
+
+	f, err := pgtype.Numeric{NaN: true, Valid: true}.Float64Value()
+	assert.NoError(t, err)
+	assert.True(t, math.IsNaN(f.Float))
+	assert.True(t, f.Valid)
+}
+
 func TestNumericCodecFuzz(t *testing.T) {
 	r := rand.New(rand.NewSource(0))
 	max := &big.Int{}