[jdbc-v2] Add support of custom type mapping via properties

[chernser]

Description

There is a typeMappings in V1 that allows user to set custom type mapping

See example: https://github.com/ClickHouse/clickhouse-tableau-connector-jdbc/blob/5dbd2b1f78e93dc8e0e95cf16460c3d50bf83743/clickhouse_jdbc/connectionBuilder.js#L39

JDBC V2 has another format of properties. In this case we need to add a new one jdbc_type_map and support typeMappings but mark as deprecated.

JDBC driver should parser string and create a type mapping that should be followed by ResultSet implementaion.

[kishansinghifs1]

Can I work on this? @chernser

[chernser]

Good day, @kishansinghifs1 !

Thank you for suggesting help!
But I have to make this task because it is time critical and requires some internal discussions.

[kishansinghifs1]

Thank for the response @chernser .

[chernser]

Triage
JDBC V1 supported configuration parameter to pass custom type mapping that was used in ResultSet implementation to convert some values to some other values. The main problem with converting values arise from complex types. Usually they may loose information about conversion. Currently client v2 has simple type hinting in most readers that help to convert some types to another while reading data.
First of all we need to support mapping primitive types (numbers) to string. However we need to define in documentation limitations of current implementation because custom type mapping requires more complex changes in client and jdbc driver.
JDBC also has ResultSetMetadata implementation that should be returned correct mapped type. In this case it looks like - column mapped to String then metadata should return column metadata as if it is string. This is the problem of consistency.
In case of JDBC this mapping will be requested on connection level and will affect all operation. This may become a problem for applications that use same connection for getting DataBaseMetadata and user data. In the first one there is strict requirement to return data in certain format and data types. So application should be prepared and use uniform code to read both metadata and user data.