fix: use fetchone() instead of rowcount and quote job metadata columns

Three additional backend-agnostic fixes:

- table.py: is_declared uses fetchone() instead of rowcount — DBAPI2
  does not guarantee rowcount for non-DML statements, breaking on
  some PostgreSQL drivers.

- schemas.py: Schema.exists uses fetchone() instead of rowcount —
  same DBAPI2 portability issue.

- autopopulate.py: _update_job_metadata uses adapter.quote_identifier()
  for _job_start_time, _job_duration, _job_version columns — these
  were hardcoded with MySQL backticks, broken on PostgreSQL.

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

Author: 3 people

src/datajoint/autopopulate.py

@@ -776,9 +776,10 @@ 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 "
-            "`_job_start_time`=%s, `_job_duration`=%s, `_job_version`=%s "
+            f"{q('_job_start_time')}=%s, {q('_job_duration')}=%s, {q('_job_version')}=%s "
             f"WHERE {pk_condition}",
             args=(start_time, duration, version[:64] if version else ""),
         )

src/datajoint/schemas.py

@@ -427,7 +427,7 @@ def exists(self) -> bool:
         """
         if self.database is None:
             raise DataJointError("Schema must be activated first.")
-        return bool(self.connection.query(self.connection.adapter.schema_exists_sql(self.database)).rowcount)
+        return self.connection.query(self.connection.adapter.schema_exists_sql(self.database)).fetchone() is not None
 
     @property
     def lineage_table_exists(self) -> bool:

src/datajoint/table.py

@@ -457,7 +457,7 @@ def is_declared(self):
             True if the table is declared in the schema.
         """
         query = self.connection.adapter.get_table_info_sql(self.database, self.table_name)
-        return self.connection.query(query).rowcount > 0
+        return self.connection.query(query).fetchone() is not None
 
     @property
     def full_table_name(self):