Fix documentation for Rows.RawValues and test new behavior

conn.go

@@ -864,8 +864,8 @@ func (c *Conn) QueryRow(ctx context.Context, sql string, args ...any) Row {
 type QueryFuncRow interface {
 	FieldDescriptions() []pgproto3.FieldDescription
 
-	// RawValues returns the unparsed bytes of the row values. The returned [][]byte is only valid during the current
-	// function call. However, the underlying byte data is safe to retain a reference to and mutate.
+	// RawValues returns the unparsed bytes of the row values. The returned data is only valid during the current
+	// function call.
 	RawValues() [][]byte
 }
 

conn_test.go

@@ -1,6 +1,7 @@
 package pgx_test
 
 import (
+	"bytes"
 	"context"
 	"os"
 	"strings"
@@ -1053,3 +1054,34 @@ func TestInsertDurationInterval(t *testing.T) {
 		require.EqualValues(t, 1, n)
 	})
 }
+
+func TestRawValuesUnderlyingMemoryReused(t *testing.T) {
+	defaultConnTestRunner.RunTest(context.Background(), t, func(ctx context.Context, t testing.TB, conn *pgx.Conn) {
+		var buf []byte
+
+		rows, err := conn.Query(ctx, `select 1::int`)
+		require.NoError(t, err)
+
+		for rows.Next() {
+			buf = rows.RawValues()[0]
+		}
+
+		require.NoError(t, rows.Err())
+
+		original := make([]byte, len(buf))
+		copy(original, buf)
+
+		for i := 0; i < 1_000_000; i++ {
+			rows, err := conn.Query(ctx, `select $1::int`, i)
+			require.NoError(t, err)
+			rows.Close()
+			require.NoError(t, rows.Err())
+
+			if bytes.Compare(original, buf) != 0 {
+				return
+			}
+		}
+
+		t.Fatal("expected buffer from RawValues to be overwritten by subsequent queries but it was not")
+	})
+}

rows.go

@@ -51,8 +51,8 @@ type Rows interface {
 	// true.
 	Values() ([]any, error)
 
-	// RawValues returns the unparsed bytes of the row values. The returned [][]byte is only valid until the next Next
-	// call or the Rows is closed. However, the underlying byte data is safe to retain a reference to and mutate.
+	// RawValues returns the unparsed bytes of the row values. The returned data is only valid until the next Next
+	// call or the Rows is closed.
 	RawValues() [][]byte
 }