[jira] [Created] (FLINK-3738) Refactor TableEnvironment and TranslationContext

["Fabian Hueske (JIRA)" <ji...@apache.org>]

Fabian Hueske created FLINK-3738:
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             Summary: Refactor TableEnvironment and TranslationContext
                 Key: FLINK-3738
                 URL: https://issues.apache.org/jira/browse/FLINK-3738
             Project: Flink
          Issue Type: Task
          Components: Table API
            Reporter: Fabian Hueske


Currently the TableAPI uses a static object called {{TranslationContext}} which holds the Calcite table catalog and a Calcite planner instance. Whenever a {{DataSet}} or {{DataStream}} is converted into a {{Table}} or registered as a {{Table}} on the {{TableEnvironment}}, a new entry is added to the catalog. The first time a {{Table}} is added, a planner instance is created. The planner is used to optimize the query (defined by one or more Table API operations and/or one ore more SQL queries) when a {{Table}} is converted into a {{DataSet}} or {{DataStream}}. Since a planner may only be used to optimize a single program, the choice of a single static object is problematic.

I propose to refactor the {{TableEnvironment}} to take over the responsibility of holding the catalog and the planner instance. 

- A {{TableEnvironment}} holds a catalog of registered tables and a single planner instance.
- A {{TableEnvironment}} will only allow to translate a single {{Table}} (possibly composed of several Table API operations and SQL queries) into a {{DataSet}} or {{DataStream}}. 
- A {{TableEnvironment}} is bound to an {{ExecutionEnvironment}} or a {{StreamExecutionEnvironment}}. This is necessary to create data source or source functions to read external tables or streams.
- {{DataSet}} and {{DataStream}} need a reference to a {{TableEnvironment}} to be converted into a {{Table}}. This will prohibit implicit casts as currently supported for the DataSet Scala API.
- A {{Table}} needs a reference to the {{TableEnvironment}} it is bound to. Only tables from the same {{TableEnvironment}} can be processed together.
- The {{TranslationContext}} will be completely removed.



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