Make trigger period optional in all dialects

Author: takluyver

src/parser/mod.rs

@@ -5592,20 +5592,7 @@ impl<'a> Parser<'a> {
         }
 
         let name = self.parse_object_name(false)?;
-        let period = if dialect_of!(self is SQLiteDialect)
-            && self
-                .peek_one_of_keywords(&[
-                    Keyword::INSERT,
-                    Keyword::UPDATE,
-                    Keyword::DELETE,
-                    Keyword::TRUNCATE,
-                ])
-                .is_some()
-        {
-            None // SQLite: period can be skipped (equivalent to BEFORE)
-        } else {
-            Some(self.parse_trigger_period()?)
-        };
+        let period = self.maybe_parse(|parser| parser.parse_trigger_period())?;
 
         let events = self.parse_keyword_separated(Keyword::OR, Parser::parse_trigger_event)?;
         self.expect_keyword_is(Keyword::ON)?;

tests/sqlparser_postgres.rs

@@ -5830,7 +5830,7 @@ fn parse_create_trigger_invalid_cases() {
         ),
         (
             "CREATE TRIGGER check_update TOMORROW UPDATE ON accounts EXECUTE FUNCTION check_account_update",
-            "Expected: one of FOR or BEFORE or AFTER or INSTEAD, found: TOMORROW"
+            "Expected: one of INSERT or UPDATE or DELETE or TRUNCATE, found: TOMORROW"
         ),
         (
             "CREATE TRIGGER check_update BEFORE SAVE ON accounts EXECUTE FUNCTION check_account_update",