[#46] Make SELECT attribute optional

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/policy/grammar.ebnf

@@ -15,7 +15,7 @@ CbtStmt ::= 'CBF', Number1 (* container backup factor *)
 
 SelectStmt ::=
     'SELECT', Number1,    (* number of nodes to select without container backup factor *)
-    'IN', Clause?, Ident, (* bucket name *)
+    ('IN', Clause?, Ident)?, (* bucket name *)
     FROM, (Ident | '*'),  (* filter reference or whole netmap *)
     ('AS', Ident)?        (* optional selector name *)
 ;

pkg/policy/grammar.go

@@ -28,8 +28,7 @@ type replicaStmt struct {
 
 type selectorStmt struct {
 	Count  uint32   `"SELECT" @Int`
-	Clause string `"IN" @("SAME" | "DISTINCT")?`
+	Bucket []string `("IN" @(("SAME" | "DISTINCT")? Ident))?`
-	Bucket string `@Ident`
 	Filter string   `"FROM" @(Ident | "*")`
 	Name   string   `("AS" @Ident)?`
 }

pkg/policy/query.go

@@ -52,18 +52,16 @@ func Parse(s string) (*netmap.PlacementPolicy, error) {
 			return nil, fmt.Errorf("%w: '%s'", ErrUnknownFilter, qs.Filter)
 		}
 		s := new(netmap.Selector)
-		switch qs.Clause {
+		switch len(qs.Bucket) {
-		case "SAME":
+		case 1: // only bucket
-			s.SetClause(netmap.Same)
+			s.SetAttribute(qs.Bucket[0])
-		case "DISTINCT":
+		case 2: // clause + bucket
-			s.SetClause(netmap.Distinct)
+			s.SetClause(clauseFromString(qs.Bucket[0]))
-		default:
+			s.SetAttribute(qs.Bucket[1])
-			s.SetClause(netmap.UnspecifiedClause)
 		}
 		s.SetName(qs.Name)
 		seenSelectors[qs.Name] = true
 		s.SetFilter(qs.Filter)
-		s.SetAttribute(qs.Bucket)
 		if qs.Count == 0 {
 			return nil, fmt.Errorf("%w: SELECT", ErrInvalidNumber)
 		}
@@ -95,6 +93,17 @@ func Parse(s string) (*netmap.PlacementPolicy, error) {
 	return p, nil
 }
 
+func clauseFromString(s string) netmap.Clause {
+	switch strings.ToUpper(s) {
+	case "SAME":
+		return netmap.Same
+	case "DISTINCT":
+		return netmap.Distinct
+	default:
+		return netmap.UnspecifiedClause
+	}
+}
+
 func filterFromOrChain(expr *orChain, seen map[string]bool) (*netmap.Filter, error) {
 	var fs []*netmap.Filter
 	for _, ac := range expr.Clauses {

pkg/policy/query_test.go

@@ -48,6 +48,39 @@ SELECT 1 IN City FROM * AS SPB`
 	require.Equal(t, expected, r)
 }
 
+// https://github.com/nspcc-dev/neofs-node/issues/46
+func TestFromSelectNoAttribute(t *testing.T) {
+	t.Run("Simple", func(t *testing.T) {
+		q := `REP 2
+		SELECT 6 FROM *`
+
+		expected := new(netmap.PlacementPolicy)
+		expected.SetFilters([]*netmap.Filter{})
+		expected.SetSelectors([]*netmap.Selector{newSelector(6, netmap.UnspecifiedClause, "", "*", "")})
+		expected.SetReplicas([]*netmap.Replica{newReplica("", 2)})
+
+		r, err := Parse(q)
+		require.NoError(t, err)
+		require.Equal(t, expected, r)
+
+	})
+
+	t.Run("with filter", func(t *testing.T) {
+		q := `REP 2
+		SELECT 6 FROM F
+		FILTER StorageType EQ SSD AS F`
+
+		expected := new(netmap.PlacementPolicy)
+		expected.SetFilters([]*netmap.Filter{newFilter("F", "StorageType", "SSD", netmap.EQ)})
+		expected.SetSelectors([]*netmap.Selector{newSelector(6, netmap.UnspecifiedClause, "", "F", "")})
+		expected.SetReplicas([]*netmap.Replica{newReplica("", 2)})
+
+		r, err := Parse(q)
+		require.NoError(t, err)
+		require.Equal(t, expected, r)
+	})
+}
+
 func TestFromSelectClause(t *testing.T) {
 	q := `REP 4
 SELECT 3 IN Country FROM *