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https://issues.apache.org/jira/browse/FLINK-15556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17013453#comment-17013453
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godfrey he edited comment on FLINK-15556 at 1/12/20 11:00 AM:
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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 a specific
table instead of the whole plan.
was (Author: godfreyhe):
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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