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https://issues.apache.org/jira/browse/FLINK-3738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15241332#comment-15241332
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ASF GitHub Bot commented on FLINK-3738:
---------------------------------------
Github user vasia commented on a diff in the pull request:
https://github.com/apache/flink/pull/1887#discussion_r59735189
--- Diff: docs/apis/batch/libs/table.md ---
@@ -61,58 +59,73 @@ Note that the Table API is currently not part of the
binary distribution. See li
Table API
----------
-The Table API provides methods for running relational operations on
Tables, both in Scala and Java.
-In the following sections you can find examples that show how to create
Tables, how to define and execute relational queries on them,
-and how to retrieve the result of a query as a `DataSet`.
+The Table API provides methods to apply relational operations on DataSets,
both in Scala and Java.
+
+The central concept of the Table API is a `Table` which is represents a
table with relational schema (or relation). Tables can be created from a
`DataSet`, converted into a `DataSet`, or registered in a table catalog using a
`TableEnvironment`. A `Table` is always bound to a specific `TableEnvironment`.
It is not possible to combine Tables of different TableEnvironments.
--- End diff --
Remove "is".
> 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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