fix: parse VALIDATE CONSTRAINT as a structured action in every dialect

ALTER TABLE t VALIDATE CONSTRAINT ck was a structured RelationAlterAction
only with the PostgreSQL dialect. Elsewhere the remaining text became
an UNSPECIFIC expression, so the constraint name could not be read and
the action could not follow an ADD that now parses in every dialect.

VALIDATE CONSTRAINT starts no other ALTER TABLE action, so recognise it
in every dialect. Its output is unchanged.

Signed-off-by: minleejae <mmj9808@gmail.com>

Author: minleejae

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -3050,6 +3050,8 @@ public class CCJSqlParser extends AbstractJSqlParser<CCJSqlParser> {
                 && "EXPRESSION".equalsIgnoreCase(getToken(columnActionOffset + 1).image)) {
             return true;
         }
+        // VALIDATE CONSTRAINT starts no other ALTER TABLE action in any dialect.
+        if (first.kind == K_VALIDATE && getToken(2).kind == K_CONSTRAINT) { return true; }
         if (!Dialect.POSTGRESQL.name().equals(getAsString(Feature.dialect))) { return false; }
         if (first.kind == K_VALIDATE || first.kind == K_RESET || isKeywordAhead("INHERIT")
                 || isKeywordAhead("REPLICA") || isKeywordAhead("OWNER") || isKeywordAhead("CLUSTER")

src/test/java/net/sf/jsqlparser/statement/alter/PostgreSqlRelationAlterTest.java

@@ -229,6 +229,23 @@ void bulkTablespaceMovesShareOneModel(String objectType) throws JSQLParserExcept
         assertEquals(2, CCJSqlParserUtil.parseStatements(statement + "; SELECT 1").size());
     }
 
+    @Test
+    void validateConstraintIsStructuredWithoutThePostgreSqlDialect() throws JSQLParserException {
+        for (Dialect dialect : new Dialect[] {null, Dialect.ANSI_SQL, Dialect.MYSQL}) {
+            Alter alter = (Alter) assertSqlCanBeParsedAndDeparsed(
+                    "ALTER TABLE t ADD CHECK (c > 0) NOT VALID, VALIDATE CONSTRAINT ck", true,
+                    p -> {
+                        if (dialect != null) {
+                            p.withDialect(dialect);
+                        }
+                    });
+            RelationAlterAction validate = assertInstanceOf(RelationAlterAction.class,
+                    alter.getAlterExpressions().get(1));
+            assertEquals(RelationAlterAction.Kind.VALIDATE_CONSTRAINT, validate.getKind());
+            assertEquals("ck", validate.getConstraintName());
+        }
+    }
+
     private static Statement parse(String sql) throws JSQLParserException {
         return CCJSqlParserUtil.parse(sql, p -> p.withDialect(Dialect.POSTGRESQL));
     }