fix ParserImpl reuse bug

src/main/java/com/wn/dbml/compiler/parser/ParserImpl.java

@@ -18,12 +18,13 @@
  * The default parser implementation.
  */
 public class ParserImpl implements Parser {
-	private final List<RelationshipDefinition> relationshipDefinitions = new ArrayList<>();
+	private List<RelationshipDefinition> relationshipDefinitions;
 	private TokenAccess tokenAccess;
 	private Database database;
 
 	@Override
 	public Database parse(final Lexer lexer) {
+		relationshipDefinitions = new ArrayList<>();
 		tokenAccess = new TokenAccess(lexer);
 		database = new Database();
 		loop:

src/test/java/com/wn/dbml/compiler/ParserTest.java

@@ -18,7 +18,32 @@ private Database parse(final String dbml) {
 	private Schema getDefaultSchema(final Database database) {
 		return database.getSchema(Schema.DEFAULT_NAME);
 	}
-
+
+	@Test
+	void testParseTwice() {
+		var dbml = """
+				Table schema1.table1 {
+				  id integer
+				  column1 integer
+				}
+				
+				Table schema2.table2 {
+				  id integer
+				  column2 integer
+				}
+				
+				Ref r1: schema2.table2.column2 - schema1.table1.column1""";
+        var parser = new ParserImpl();
+
+		var database = parser.parse(new LexerImpl(dbml));
+		var relationships = database.getRelationships();
+		assertEquals(1, relationships.size());
+
+		database = parser.parse(new LexerImpl(dbml));
+		relationships = database.getRelationships();
+		assertEquals(1, relationships.size());
+	}
+
 	@Test
 	void testParseProject() {
 		var dbml = """