RFC: Resolve "Improve connection mgmt in `dbconn.BaseClient`"

Closes #12 (closed)

BaseClient

• (uses: username, database, host, port, password args)
• has conn_url prop

Engine Based (mostly SQLAlchemy based):

• PgClient
• MySqlClient
• OracleClient
• SqliteClient
• SqlServerClient

Special case

• HiveClient

Client based:

• MongoClient
• IbisClient
• BigQueryClient

Feature requests

• AthenaClient (ClientBased?)
• TeradataClient (ClientBased?)

Commons for all clients

• methods
  • execute query (execute)
  • get data from query to dataframe (to_frame)
  • insert data from dataframe (insert_from_frame)
• properties
  • conn_url

BaseClient should implement this interface.

Engine based clients

These clients should create and destroy connections on the fly as to not have dangling connections.

• get_engine

A new SessionBaseClient should implement this interface.

Transactions

We should discuss whether we need transactions to be implemented or are needed at all. In such case, we should implement that logic, but that's out of scope.

ToDo

Client Based Clients (clientception)

• Ibis
• Mongo
• BigQuery