Treat nil []byte in query parameters as nil/NULL rather than ""

Co-authored-by: Martin Tournoij <[email protected]>

Author: epelc

CHANGELOG.md

@@ -53,8 +53,11 @@ newer. Previously PostgreSQL 8.4 and newer were supported.
 
 - Handle ErrorResponse in readReadyForQuery and return proper error ([#1136]).
 
+- Treat nil []byte in query parameters as nil/NULL rather than `""` ([#838]).
+
 [#595]: https://github.com/lib/pq/pull/595
 [#745]: https://github.com/lib/pq/pull/745
+[#838]: https://github.com/lib/pq/pull/838
 [#949]: https://github.com/lib/pq/pull/949
 [#1125]: https://github.com/lib/pq/pull/1125
 [#1129]: https://github.com/lib/pq/pull/1129

conn.go

@@ -1479,8 +1479,12 @@ func (st *stmt) exec(v []driver.NamedValue) {
 				w.int32(-1)
 			} else {
 				b := encode(&cn.parameterStatus, x.Value, st.paramTyps[i])
-				w.int32(len(b))
-				w.bytes(b)
+				if b == nil {
+					w.int32(-1)
+				} else {
+					w.int32(len(b))
+					w.bytes(b)
+				}
 			}
 		}
 	}
@@ -1746,9 +1750,8 @@ func md5s(s string) string {
 }
 
 func (cn *conn) sendBinaryParameters(b *writeBuf, args []driver.NamedValue) {
-	// Do one pass over the parameters to see if we're going to send any of
-	// them over in binary.  If we are, create a paramFormats array at the
-	// same time.
+	// Do one pass over the parameters to see if we're going to send any of them
+	// over in binary.  If we are, create a paramFormats array at the same time.
 	var paramFormats []int
 	for i, x := range args {
 		_, ok := x.Value.([]byte)
@@ -1772,6 +1775,8 @@ func (cn *conn) sendBinaryParameters(b *writeBuf, args []driver.NamedValue) {
 	for _, x := range args {
 		if x.Value == nil {
 			b.int32(-1)
+		} else if xx, ok := x.Value.([]byte); ok && xx == nil {
+			b.int32(-1)
 		} else {
 			datum := binaryEncode(&cn.parameterStatus, x.Value)
 			b.int32(len(datum))

conn_test.go

@@ -192,6 +192,54 @@ localhost:*:*:*:pass_C
 	assertPassword(values{"host": "server", "passfile": pgpassFile, "dbname": "some_db", "user": "some_user"}, "pass_A")
 }
 
+func TestExecNilSlice(t *testing.T) {
+	db := pqtest.MustDB(t)
+	defer db.Close()
+
+	_, err := db.Exec("create temp table x (b1 text, b2 text, b3 text)")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var (
+		b1 []byte
+		b2 []string
+		b3 = []byte{}
+	)
+	_, err = db.Exec("insert into x (b1, b2, b3) values ($1, $2, $3)", b1, b2, b3)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rows, err := db.Query(`select * from x`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rows.Close()
+	for rows.Next() {
+		if rows.Err() != nil {
+			t.Fatal(rows.Err())
+		}
+		var b1, b2, b3 *string
+		err = rows.Scan(&b1, &b2, &b3)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		deref := func(s *string) string {
+			if s == nil {
+				return "<nil>"
+			}
+			return fmt.Sprintf("%q", *s)
+		}
+
+		want := `b1=<nil>; b2=<nil>; b3=""`
+		have := fmt.Sprintf("b1=%s; b2=%s; b3=%s", deref(b1), deref(b2), deref(b3))
+		if want != have {
+			t.Errorf("\nwant: %s\nhave: %s", want, have)
+		}
+	}
+}
+
 func TestExec(t *testing.T) {
 	db := pqtest.MustDB(t)
 	defer db.Close()
@@ -205,7 +253,6 @@ func TestExec(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-
 	if n, _ := r.RowsAffected(); n != 1 {
 		t.Fatalf("expected 1 row affected, not %d", n)
 	}
@@ -214,29 +261,24 @@ func TestExec(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-
 	if n, _ := r.RowsAffected(); n != 3 {
 		t.Fatalf("expected 3 rows affected, not %d", n)
 	}
 
-	// SELECT doesn't send the number of returned rows in the command tag
-	// before 9.0
-	if getServerVersion(t, db) >= 90000 {
-		r, err = db.Exec("SELECT g FROM generate_series(1, 2) g")
-		if err != nil {
-			t.Fatal(err)
-		}
-		if n, _ := r.RowsAffected(); n != 2 {
-			t.Fatalf("expected 2 rows affected, not %d", n)
-		}
+	r, err = db.Exec("SELECT g FROM generate_series(1, 2) g")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n, _ := r.RowsAffected(); n != 2 {
+		t.Fatalf("expected 2 rows affected, not %d", n)
+	}
 
-		r, err = db.Exec("SELECT g FROM generate_series(1, $1) g", 3)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if n, _ := r.RowsAffected(); n != 3 {
-			t.Fatalf("expected 3 rows affected, not %d", n)
-		}
+	r, err = db.Exec("SELECT g FROM generate_series(1, $1) g", 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n, _ := r.RowsAffected(); n != 3 {
+		t.Fatalf("expected 3 rows affected, not %d", n)
 	}
 }
 

encode.go

@@ -35,26 +35,25 @@ func encode(parameterStatus *parameterStatus, x any, pgtypOid oid.Oid) []byte {
 	case float64:
 		return strconv.AppendFloat(nil, v, 'f', -1, 64)
 	case []byte:
+		if v == nil {
+			return nil
+		}
 		if pgtypOid == oid.T_bytea {
 			return encodeBytea(parameterStatus.serverVersion, v)
 		}
-
 		return v
 	case string:
 		if pgtypOid == oid.T_bytea {
 			return encodeBytea(parameterStatus.serverVersion, []byte(v))
 		}
-
 		return []byte(v)
 	case bool:
 		return strconv.AppendBool(nil, v)
 	case time.Time:
 		return formatTs(v)
-
 	default:
 		errorf("encode: unknown type for %T", v)
 	}
-
 	panic("not reached")
 }