Add Postgres table adapter with TableRepositoryInterface.

Introduce PostgresAdapter for dict-based row CRUD via psycopg3, including config, lazy exports, unit/integration tests with testcontainers, and an example UserTableRepository.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/connection_aware_adapter_test.py

@@ -6,10 +6,12 @@ from typing import cast
 from unittest.mock import MagicMock, patch
 
 import redis
+import psycopg
 
 from python_repositories.adapters.minio_adapter import MinioAdapter
+from python_repositories.adapters.postgres_adapter import PostgresAdapter
 from python_repositories.adapters.redis_adapter import RedisAdapter
-from tests.conftest import TEST_MINIO_CONFIG, TEST_REDIS_CONFIG
+from tests.conftest import TEST_MINIO_CONFIG, TEST_POSTGRES_CONFIG, TEST_REDIS_CONFIG
 
 
 class TestRedisConnectionHealth:
@@ -161,3 +163,74 @@ class TestMinioConnectionHealth:
             assert reinjected.is_connected()
 
         assert mock_client.bucket_exists.call_count == 2
+
+
+class TestPostgresConnectionHealth:
+    def test_not_connected_when_no_client(self) -> None:
+        adapter = PostgresAdapter(config=TEST_POSTGRES_CONFIG)
+        assert not adapter.is_connected()
+
+    def test_connected_when_probe_succeeds(
+        self, postgres_adapter: PostgresAdapter
+    ) -> None:
+        assert postgres_adapter.is_connected()
+        cast(MagicMock, postgres_adapter._client).cursor.assert_called()
+
+    def test_stale_connection_when_probe_fails(
+        self, postgres_adapter: PostgresAdapter
+    ) -> None:
+        mock_cursor = cast(MagicMock, postgres_adapter._client).cursor.return_value
+        mock_cursor.execute.side_effect = psycopg.OperationalError("connection lost")
+
+        assert not postgres_adapter.is_connected()
+
+    def test_cache_hit_avoids_second_probe(
+        self, postgres_adapter: PostgresAdapter
+    ) -> None:
+        mock_client = cast(MagicMock, postgres_adapter._client)
+
+        with patch(
+            "python_repositories.adapters.connection_aware_adapter.time.monotonic",
+            return_value=100.0,
+        ):
+            assert postgres_adapter.is_connected()
+            assert postgres_adapter.is_connected()
+
+        assert mock_client.cursor.call_count == 1
+
+    def test_cache_miss_runs_probe_again(
+        self, postgres_adapter: PostgresAdapter
+    ) -> None:
+        mock_client = cast(MagicMock, postgres_adapter._client)
+
+        with patch(
+            "python_repositories.adapters.connection_aware_adapter.time.monotonic",
+            side_effect=[100.0, 102.0],
+        ):
+            assert postgres_adapter.is_connected()
+            assert postgres_adapter.is_connected()
+
+        assert mock_client.cursor.call_count == 2
+
+    def test_disconnect_clears_cache(self, postgres_adapter: PostgresAdapter) -> None:
+        mock_client = cast(MagicMock, postgres_adapter._client)
+
+        with patch(
+            "python_repositories.adapters.connection_aware_adapter.time.monotonic",
+            return_value=100.0,
+        ):
+            assert postgres_adapter.is_connected()
+
+        postgres_adapter.disconnect()
+        reinjected = PostgresAdapter(
+            config=postgres_adapter._config,
+            client=mock_client,
+        )
+
+        with patch(
+            "python_repositories.adapters.connection_aware_adapter.time.monotonic",
+            return_value=100.0,
+        ):
+            assert reinjected.is_connected()
+
+        assert mock_client.cursor.call_count == 2