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https://issues.apache.org/jira/browse/FLINK-3738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15238719#comment-15238719
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Yijie Shen commented on FLINK-3738:
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Hi [~fhueske], your idea make much sense to me.
Besides you have mentioned above, I think it's worthwhile to rethink the
*validation* of plan generated from our Table API.
Currently, out validation codes are scattered mainly in two places: in table
API's RelNode construction, and in code generation. Regarding the lifecycle of
query execution, it's scattered in logical plan generation and physical plan
generation. Since table API & sql execution share the code generation path, the
validation here is inappropriate.
Therefore, I think we could possibly extract the validation into a single
phase, between table API call and RelNode construction, similar to the planning
procedure of SQL String execution.
> 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
> Assignee: 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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