apiserver needs full sql test, pay attention to NsClient::db_

Each apiserver request has its own db, but NsClient used to cache db. So we may get no db bug when we request apiserver and it calls NsClient.

The issue mentions apiserver, NsClient::db_, and a potential 'no db bug'. Look for apiserver request handling code and the NsClient class to understand how database connections are managed and cached. Write a full SQL test that reproduces the scenario where a request triggers NsClient and encounters a missing database. Verify the fix ensures each request has its own db accessible.

索引モデルが issue の本文から書いたものです。