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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-6442) Extend TableAPI Support Sink Table Registration and ‘insert into’ Clause in SQL
Date Mon, 04 Sep 2017 15:57:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-6442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16152746#comment-16152746
] 

ASF GitHub Bot commented on FLINK-6442:
---------------------------------------

Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3829#discussion_r136847905
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/queryConfig.scala
---
    @@ -19,9 +19,21 @@
     package org.apache.flink.table.api
     
     import _root_.java.io.Serializable
    +
     import org.apache.flink.api.common.time.Time
     
    -class QueryConfig private[table] extends Serializable {}
    +class QueryConfig private[table] extends Serializable {
    +}
    +
    +object QueryConfig {
    +  def getQueryConfigFromTableEnv(tableEnv: TableEnvironment): QueryConfig = {
    --- End diff --
    
    The problem is that we should have the correct subtype of `QueryConfig` (not only the
returned object but also the method signature) and the separation of the stream and batch
APIs. The `StreamExecutionEnvironment.queryConfig` method must be typed to `StreamQueryConfig`
to prevent casting. However, we don't want to have a method that is typed to `StreamQueryConfig`
in the base class `TableEnvironment` because 1) this class should be independent from the
streaming API and 2) we don't want a streaming method in the `BatchTableEnvironment`.
    
    So, we can add a method to `TableEnvironment` that returns `QueryConfig` (depending on
its own type a `StreamQueryConfig` or `BatchQueryConfig`) and override this method in `StreamTableEnvironment`
such that it returns a `StreamQueryConfig` (and if later necessary in `BatchTableEnvironment`
to return a `BatchQueryConfig`).
    
    The duplicated code are < 5 lines and we have correct types everywhere. 


> Extend TableAPI Support Sink Table Registration and ‘insert into’ Clause in SQL
> -------------------------------------------------------------------------------
>
>                 Key: FLINK-6442
>                 URL: https://issues.apache.org/jira/browse/FLINK-6442
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: lincoln.lee
>            Assignee: lincoln.lee
>            Priority: Minor
>
> Currently in TableAPI  there’s only registration method for source table,  when we
use SQL writing a streaming job, we should add additional part for the sink, like TableAPI
does:
> {code}
> val sqlQuery = "SELECT * FROM MyTable WHERE _1 = 3"
> val t = StreamTestData.getSmall3TupleDataStream(env)
> tEnv.registerDataStream("MyTable", t)
> // one way: invoke tableAPI’s writeToSink method directly
> val result = tEnv.sql(sqlQuery)
> result.writeToSink(new YourStreamSink)
> // another way: convert to datastream first and then invoke addSink 
> val result = tEnv.sql(sqlQuery).toDataStream[Row]
> result.addSink(new StreamITCase.StringSink)
> {code}
> From the api we can see the sink table always be a derived table because its 'schema'
is inferred from the result type of upstream query.
> Compare to traditional RDBMS which support DML syntax, a query with a target output could
be written like this:
> {code}
> insert into table target_table_name
> [(column_name [ ,...n ])]
> query
> {code}
> The equivalent form of the example above is as follows:
> {code}
>     tEnv.registerTableSink("targetTable", new YourSink)
>     val sql = "INSERT INTO targetTable SELECT a, b, c FROM sourceTable"
>     val result = tEnv.sql(sql)
> {code}
> It is supported by Calcite’s grammar: 
> {code}
>  insert:( INSERT | UPSERT ) INTO tablePrimary
>  [ '(' column [, column ]* ')' ]
>  query
> {code}
> I'd like to extend Flink TableAPI to support such feature.  see design doc: https://goo.gl/n3phK5



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