fix: Dialect class isn't looked up for external drivers

Author: paveltiunov

packages/cubejs-schema-compiler/adapter/QueryBuilder.js

@@ -38,9 +38,17 @@ exports.query = (compilers, dbType, queryOptions) => {
     return null;
   }
 
+  let externalQueryClass = queryOptions.externalDialectClass;
+
+  if (!externalQueryClass) {
+    if (!ADAPTERS[queryOptions.externalDbType]) {
+      throw new Error(`Dialect for '${queryOptions.externalDbType}' is not found`);
+    }
+    externalQueryClass = queryOptions.externalDbType && ADAPTERS[queryOptions.externalDbType];
+  }
+
   return new (queryOptions.dialectClass || ADAPTERS[dbType])(compilers, {
     ...queryOptions,
-    externalQueryClass: queryOptions.externalDialectClass ||
-      queryOptions.externalDbType && ADAPTERS[queryOptions.externalDbType]
+    externalQueryClass
   });
 };

packages/cubejs-server-core/core/index.js

@@ -168,6 +168,9 @@ class CubejsServerCore {
           password: process.env.CUBEJS_EXT_DB_PASS,
         })
       ),
+      externalDialectFactory: () => typeof options.externalDbType === 'string' &&
+        CubejsServerCore.lookupDriverClass(options.externalDbType).dialectClass &&
+        CubejsServerCore.lookupDriverClass(options.externalDbType).dialectClass(),
       externalDbType: process.env.CUBEJS_EXT_DB_TYPE,
       apiSecret: process.env.CUBEJS_API_SECRET,
       dbType: process.env.CUBEJS_DB_TYPE,