Add test for DirectQueryDriver with PostgreSQL.

This has some failures that I've marked as expected until we try to fix
them again on DM-43697.

tests/test_query_direct_postgresql.py

@@ -0,0 +1,117 @@
+# This file is part of daf_butler.
+#
+# Developed for the LSST Data Management System.
+# This product includes software developed by the LSST Project
+# (https://www.lsst.org).
+# See the COPYRIGHT file at the top-level directory of this distribution
+# for details of code ownership.
+#
+# This software is dual licensed under the GNU General Public License and also
+# under a 3-clause BSD license. Recipients may choose which of these licenses
+# to use; please see the files gpl-3.0.txt and/or bsd_license.txt,
+# respectively.  If you choose the GPL option then the following text applies
+# (but note that there is still no warranty even if you opt for BSD instead):
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+"""Tests for DirectButler._query with PostgreSQL.
+"""
+
+from __future__ import annotations
+
+import gc
+import os
+import secrets
+import unittest
+
+try:
+    # It's possible but silly to have testing.postgresql installed without
+    # having the postgresql server installed (because then nothing in
+    # testing.postgresql would work), so we use the presence of that module
+    # to test whether we can expect the server to be available.
+    import testing.postgresql
+except ImportError:
+    testing = None
+import sqlalchemy
+from lsst.daf.butler import Butler, ButlerConfig, StorageClassFactory
+from lsst.daf.butler.datastore import NullDatastore
+from lsst.daf.butler.direct_butler import DirectButler
+from lsst.daf.butler.registry.sql_registry import SqlRegistry
+from lsst.daf.butler.tests.butler_queries import ButlerQueryTests
+from lsst.daf.butler.tests.utils import makeTestTempDir, removeTestTempDir
+
+TESTDIR = os.path.abspath(os.path.dirname(__file__))
+
+
+def _start_server(root):
+    """Start a PostgreSQL server and create a database within it, returning
+    an object encapsulating both.
+    """
+    server = testing.postgresql.Postgresql(base_dir=root)
+    engine = sqlalchemy.create_engine(server.url())
+    with engine.begin() as connection:
+        connection.execute(sqlalchemy.text("CREATE EXTENSION btree_gist;"))
+    return server
+
+
+@unittest.skipUnless(testing is not None, "testing.postgresql module not found")
+class DirectButlerPostgreSQLTests(ButlerQueryTests, unittest.TestCase):
+    """Tests for DirectButler._query with PostgreSQL."""
+
+    data_dir = os.path.join(TESTDIR, "data/registry")
+
+    @classmethod
+    def setUpClass(cls):
+        cls.root = makeTestTempDir(TESTDIR)
+        cls.server = _start_server(cls.root)
+
+    @classmethod
+    def tearDownClass(cls):
+        # Clean up any lingering SQLAlchemy engines/connections
+        # so they're closed before we shut down the server.
+        gc.collect()
+        cls.server.stop()
+        removeTestTempDir(cls.root)
+
+    def make_butler(self, *args: str) -> Butler:
+        config = ButlerConfig()
+        config[".registry.db"] = self.server.url()
+        config[".registry.namespace"] = f"namespace_{secrets.token_hex(8).lower()}"
+        registry = SqlRegistry.createFromConfig(config)
+        for arg in args:
+            self.load_data(registry, arg)
+        return DirectButler(
+            config=config,
+            registry=registry,
+            datastore=NullDatastore(None, None),
+            storageClasses=StorageClassFactory(),
+        )
+
+    # TODO (DM-43697): these tests fail due to something going awry with cursor
+    # and temporary table lifetime management; PostgreSQL says we can't drop
+    # temp tables because there are still active queries against them.  The
+    # logic looks fine but is obfuscated by the many levels of competing
+    # context managers in the Database class, so we'll punt this to DM-43697.
+
+    @unittest.expectedFailure
+    def test_data_coordinate_upload_force_temp_table(self) -> None:
+        super().test_data_coordinate_upload_force_temp_table()
+
+    @unittest.expectedFailure
+    def test_materialization(self) -> None:
+        return super().test_materialization()
+
+
+if __name__ == "__main__":
+    unittest.main()