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Posted to issues@flink.apache.org by "godfrey he (Jira)" <ji...@apache.org> on 2020/01/11 12:06:00 UTC

[jira] [Commented] (FLINK-15556) Add a switch for PushProjectIntoTableSourceScanRule

    [ https://issues.apache.org/jira/browse/FLINK-15556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17013453#comment-17013453 ] 

godfrey he commented on FLINK-15556:
------------------------------------

hi [~hailong wang], if there are many different kinds of table sources in one query, it's very useful for some table sources that the project can be pushed down, while it's worse for some table sources that the source can not be reused (as you mentioned above). So the switch can't handle this case. 
One suggestion is we can introduce table hints which can affect every table instead of the whole plan.

> Add a switch for PushProjectIntoTableSourceScanRule
> ---------------------------------------------------
>
>                 Key: FLINK-15556
>                 URL: https://issues.apache.org/jira/browse/FLINK-15556
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table SQL / Planner
>    Affects Versions: 1.10.0
>            Reporter: hailong wang
>            Priority: Minor
>             Fix For: 1.11.0
>
>
> In some case, For the project push down, The  digest of tableSource maybe different. For example, If we create a jdbc tablesource, and is used twice after it for different column, the source can not be reused for the different digest. In this case, the query io will more precious, So we can add a switch to turn off project push down, and the reused the source.



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