fix: address review — drop unnecessary quoting and transaction guards

- autopopulate.py: remove quote_identifier() for _job_start_time,
  _job_duration, _job_version — these are plain identifiers that
  don't need quoting on any backend.

- connection.py: revert transaction SQL guards — both MySQL and
  PostgreSQL always return non-empty SQL. The guards were premature
  abstraction for hypothetical backends.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: dimitri-yatsenko

src/datajoint/autopopulate.py

@@ -776,10 +776,9 @@ def _update_job_metadata(self, key, start_time, duration, version):
         from .condition import make_condition
 
         pk_condition = make_condition(self, key, set())
-        q = self.connection.adapter.quote_identifier
         self.connection.query(
             f"UPDATE {self.full_table_name} SET "
-            f"{q('_job_start_time')}=%s, {q('_job_duration')}=%s, {q('_job_version')}=%s "
+            "_job_start_time=%s, _job_duration=%s, _job_version=%s "
             f"WHERE {pk_condition}",
             args=(start_time, duration, version[:64] if version else ""),
         )

src/datajoint/connection.py

@@ -486,25 +486,19 @@ def start_transaction(self) -> None:
         """
         if self.in_transaction:
             raise errors.DataJointError("Nested connections are not supported.")
-        sql = self.adapter.start_transaction_sql()
-        if sql:
-            self.query(sql)
+        self.query(self.adapter.start_transaction_sql())
         self._in_transaction = True
         logger.debug("Transaction started")
 
     def cancel_transaction(self) -> None:
         """Cancel the current transaction and roll back all changes."""
-        sql = self.adapter.rollback_sql()
-        if sql:
-            self.query(sql)
+        self.query(self.adapter.rollback_sql())
         self._in_transaction = False
         logger.debug("Transaction cancelled. Rolling back ...")
 
     def commit_transaction(self) -> None:
         """Commit all changes and close the transaction."""
-        sql = self.adapter.commit_sql()
-        if sql:
-            self.query(sql)
+        self.query(self.adapter.commit_sql())
         self._in_transaction = False
         logger.debug("Transaction committed and closed.")