refactor(dwh): adapt direct and REST transports

harness/tht/adapters/dwh/postgres.py

@@ -0,0 +1,41 @@
+"""Direct PostgreSQL implementation of the DWH port."""
+
+from tht.config import DatabaseConfig
+from tht.db import execute
+from tht.db.connection import make_engine, ping
+from tht.db.introspect import introspect
+from tht.execute import ExecResult, PlanSummary
+from tht.mschema.models import PhysicalSchema
+from tht.ports.dwh import DwhCapabilities, DwhHealth
+
+
+class PostgresDwhAdapter:
+    capabilities = DwhCapabilities()
+
+    def __init__(self, config: DatabaseConfig):
+        self._config = config
+        self._engine = make_engine(config)
+
+    def health(self) -> DwhHealth:
+        try:
+            ping(self._engine)
+        except Exception as exc:
+            return DwhHealth(ok=False, detail=str(exc))
+        return DwhHealth(ok=True)
+
+    def introspect(self) -> PhysicalSchema:
+        return introspect(self._engine, self._config.database, self._config.db_schema)
+
+    def run_query(self, sql: str, *, limit: int | None = None) -> ExecResult:
+        return execute.run_query(self._engine, sql, limit=limit)
+
+    def explain(self, sql: str) -> PlanSummary:
+        return execute.explain(self._engine, sql)
+
+    def sample_column(self, table: str, column: str, *, limit: int) -> list[object]:
+        return execute.sample_column(
+            self._engine, self._config.db_schema, table, column, limit=limit
+        )
+
+    def distinct_values(self, table: str, column: str) -> list[object]:
+        return execute.distinct_values(self._engine, self._config.db_schema, table, column)