feat: add DuckDB as a supported query engine (closes #40)

backend/src/analytics_agent/api/settings.py

@@ -214,12 +214,36 @@ class UpdateDisplayRequest(BaseModel):
         {"name": "preview_table", "label": "Preview data"},
         {"name": "execute_sql", "label": "Execute SQL"},
     ],
+    "hive": [
+        {"name": "list_tables", "label": "List tables"},
+        {"name": "get_schema", "label": "Table schema"},
+        {"name": "preview_table", "label": "Preview data"},
+        {"name": "execute_sql", "label": "Execute SQL"},
+    ],
     "mysql": [
         {"name": "list_tables", "label": "List tables"},
         {"name": "get_schema", "label": "Table schema"},
         {"name": "preview_table", "label": "Preview data"},
         {"name": "execute_sql", "label": "Execute SQL"},
     ],
+    "postgresql": [
+        {"name": "list_tables", "label": "List tables"},
+        {"name": "get_schema", "label": "Table schema"},
+        {"name": "preview_table", "label": "Preview data"},
+        {"name": "execute_sql", "label": "Execute SQL"},
+    ],
+    "sqlite": [
+        {"name": "list_tables", "label": "List tables"},
+        {"name": "get_schema", "label": "Table schema"},
+        {"name": "preview_table", "label": "Preview data"},
+        {"name": "execute_sql", "label": "Execute SQL"},
+    ],
+    "duckdb": [
+        {"name": "list_tables", "label": "List tables"},
+        {"name": "get_schema", "label": "Table schema"},
+        {"name": "preview_table", "label": "Preview data"},
+        {"name": "execute_sql", "label": "Execute SQL"},
+    ],
     "sqlalchemy": [
         {"name": "list_tables", "label": "List tables"},
         {"name": "get_schema", "label": "Table schema"},
@@ -249,6 +273,30 @@ def _build_tool_toggles(
     return result
 
 
+def _compute_engine_status(engine_type: str, conn_cfg: dict, sso_connected: bool = False) -> str:
+    """Return 'connected' or 'unconfigured' for an engine connection."""
+    from analytics_agent.engines.factory import _CONNECTOR_MAP
+
+    spec = _CONNECTOR_MAP.get(engine_type)
+    if spec is not None:
+        return (
+            "connected"
+            if spec.is_configured(conn_cfg, sso_connected=sso_connected)
+            else "unconfigured"
+        )
+
+    if engine_type in ("mysql", "sqlalchemy", "postgresql", "sqlite", "duckdb"):
+        host = conn_cfg.get("host", "")
+        database = conn_cfg.get("database", conn_cfg.get("db", ""))
+        has_url = bool(conn_cfg.get("url"))
+        # File-based engines need only `database`; server engines need host too.
+        file_based = engine_type in ("sqlite", "duckdb")
+        if has_url or (file_based and bool(database)) or (host and database):
+            return "connected"
+
+    return "unconfigured"
+
+
 # --- Connection helpers ---
 
 
@@ -596,15 +644,9 @@ async def list_connections(session: AsyncSession = Depends(get_session)):
         is_sso_connected = cred is not None and cred.auth_type == "sso_externalbrowser"
 
         if intg.type == "snowflake":
-            from analytics_agent.engines.factory import _CONNECTOR_MAP as _CM
-
             account = conn_cfg.get("account", "")
             user = conn_cfg.get("user", "")
-            status_str = (
-                "connected"
-                if _CM["snowflake"].is_configured(conn_cfg, sso_connected=is_sso_connected)
-                else "unconfigured"
-            )
+            status_str = _compute_engine_status(intg.type, conn_cfg, sso_connected=is_sso_connected)
             # Detect active auth method so the frontend can pre-select the right tab.
             if is_sso_connected:
                 active_auth_method = "sso"
@@ -667,7 +709,7 @@ async def list_connections(session: AsyncSession = Depends(get_session)):
                 conn_cfg.get(k) or os.environ.get(_CM["bigquery"].env_map.get(k, ""), "")
                 for k in _CM["bigquery"].credential_keys
             )
-            status_str = "connected" if _CM["bigquery"].is_configured(conn_cfg) else "unconfigured"
+            status_str = _compute_engine_status(intg.type, conn_cfg)
             fields = [
                 ConnectionField(
                     key="project",
@@ -690,13 +732,13 @@ async def list_connections(session: AsyncSession = Depends(get_session)):
                     placeholder='{"type":"service_account",...}',
                 ),
             ]
-        elif intg.type in ("mysql", "sqlalchemy", "postgresql", "sqlite"):
+        elif intg.type in ("mysql", "sqlalchemy", "postgresql", "sqlite", "duckdb"):
             host = conn_cfg.get("host", "")
             database = conn_cfg.get("database", conn_cfg.get("db", ""))
             port = str(conn_cfg.get("port", ""))
             user = conn_cfg.get("user", conn_cfg.get("username", ""))
             has_url = bool(conn_cfg.get("url"))
-            status_str = "connected" if (has_url or (host and database)) else "unconfigured"
+            status_str = _compute_engine_status(intg.type, conn_cfg)
             if has_url:
                 fields = [
                     ConnectionField(
@@ -736,8 +778,8 @@ async def list_connections(session: AsyncSession = Depends(get_session)):
             from analytics_agent.engines.factory import _CONNECTOR_MAP as _CM
 
             spec = _CM.get(intg.type)
+            status_str = _compute_engine_status(intg.type, conn_cfg)
             if spec is not None and spec.display_fields:
-                status_str = "connected" if spec.is_configured(conn_cfg) else "unconfigured"
                 fields = []
                 for df in spec.display_fields:
                     raw = conn_cfg.get(df.key, "") or os.environ.get(
@@ -755,7 +797,6 @@ async def list_connections(session: AsyncSession = Depends(get_session)):
                         )
                     )
             else:
-                status_str = "unconfigured"
                 fields = []
 
         oauth_status = (

backend/src/analytics_agent/engines/factory.py

@@ -187,6 +187,7 @@ def get_secret_env_vars(engine_type: str) -> dict[str, str]:
         "mysql": SQLAlchemyQueryEngine,
         "sqlite": SQLAlchemyQueryEngine,
         "postgresql": SQLAlchemyQueryEngine,
+        "duckdb": SQLAlchemyQueryEngine,
         "sqlalchemy": SQLAlchemyQueryEngine,
     }.get(engine_type)
     return getattr(cls, "secret_env_vars", {}) if cls else {}
@@ -208,6 +209,7 @@ def _make_connector(connection_cfg: dict) -> MCPQueryEngine:
         "mysql": SQLAlchemyQueryEngine,
         "sqlite": SQLAlchemyQueryEngine,
         "postgresql": SQLAlchemyQueryEngine,
+        "duckdb": SQLAlchemyQueryEngine,
         "sqlalchemy": SQLAlchemyQueryEngine,
         "mcp": MCPQueryEngine,
         "mcp-stdio": MCPQueryEngine,

frontend/src/components/Settings/connections/index.ts

@@ -8,6 +8,7 @@ import { hivePlugin } from "./plugins/hive";
 import { mysqlPlugin } from "./plugins/mysql";
 import { postgresqlPlugin } from "./plugins/postgresql";
 import { sqlitePlugin } from "./plugins/sqlite";
+import { duckdbPlugin } from "./plugins/duckdb";
 import { datahubPlugin } from "./plugins/datahub";
 import { datahubMcpPlugin } from "./plugins/datahub-mcp";
 import { customMcpEnginePlugin, customMcpContextPlugin } from "./plugins/custom-mcp";
@@ -24,6 +25,7 @@ export const CONNECTION_PLUGINS: ConnectionPlugin[] = [
   mysqlPlugin,
   postgresqlPlugin,
   sqlitePlugin,
+  duckdbPlugin,
   customMcpEnginePlugin,
 
   // Context platforms

frontend/src/components/Settings/connections/plugins/duckdb.tsx

@@ -0,0 +1,25 @@
+import { SimpleFormShell } from "../SimpleFormShell";
+import type { ConnectionPlugin, NewConnectionPayload } from "../types";
+
+const FIELDS = [
+  { key: "database", label: "Database file path", type: "mono" as const,
+    placeholder: "/absolute/path/to/database.duckdb", required: true },
+];
+
+export const duckdbPlugin: ConnectionPlugin = {
+  id: "duckdb",
+  serviceId: "duckdb",
+  label: "DuckDB",
+  category: "engine",
+  transport: "native",
+  description: "Connect to a local DuckDB database file",
+  Form: ({ onDone, onCancel }) => (
+    <SimpleFormShell
+      fields={FIELDS}
+      onCancel={onCancel}
+      onDone={(payload: NewConnectionPayload) =>
+        onDone({ ...payload, config: { dialect: "duckdb", ...payload.config } })
+      }
+    />
+  ),
+};