[jira] [Commented] (FLINK-2971) Add outer joins to the Table API

["Dawid Wysakowicz (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-2971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15259992#comment-15259992 ] 

Dawid Wysakowicz commented on FLINK-2971:
-----------------------------------------

Thanks for assigning me to this issue. I've started working on it, but I encountered a problem I wanted to discuss. I wanted to enhance {{Table}} with methods like:
{code}
  def join(right: Table): Table
  def join(right: Table, onColumns: String): Table
  def join(right: Table, onColumns: Expression): Table 
  def join(right: Table, onColumns: Expression, joinType: JoinType): Table 
{code}
Those method enable users to specify join condition and joinType (join condition pushed from {{filter}} or {{where}} disables the outer joins). Unfortunately right know it is impossible to resolve {{UnresolvedFieldReference}} to a field of one of many inputs. I proposed a solution(table.scala:437-447), but I am not sure if it is elegant enough.

My WIP branch: https://github.com/dawidwys/flink/tree/outerJoin

> Add outer joins to the Table API
> --------------------------------
>
>                 Key: FLINK-2971
>                 URL: https://issues.apache.org/jira/browse/FLINK-2971
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API
>            Reporter: Timo Walther
>            Assignee: Dawid Wysakowicz
>
> Since Flink now supports outer joins, the Table API can also support left, right and full outer joins.
> Given that null values are properly supported by RowSerializer etc.



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