[
https://issues.apache.org/jira/browse/FLINK-3848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15652132#comment-15652132
]
Fabian Hueske commented on FLINK-3848:
--------------------------------------
Yes, you're both right. The optimizer should identify that the TableSource
supports projection push-down and push the projection into the TableSource. The
user should not have to interact with the TableSource directly (apart from
registering it as a Table in the TableEnvironment).
IIRC, I had some problems specify the optimizer rules when I tried to implement
this feature. I saw [this
mail|https://lists.apache.org/thread.html/5896f4e834e976f146f280d279bf24c111c32476d96ae48d0f3c0d25@%3Cdev.calcite.apache.org%3E]
a few days ago on the Calcite dev list. Maybe it helps to define the rule.
> Add ProjectableTableSource interface and translation rule
> ---------------------------------------------------------
>
> Key: FLINK-3848
> URL: https://issues.apache.org/jira/browse/FLINK-3848
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Fabian Hueske
> Assignee: Anton Solovev
>
> Add a {{ProjectableTableSource}} interface for {{TableSource}} implementation
> that support projection push-down.
> The interface could look as follows
> {code}
> def trait ProjectableTableSource {
> def setProjection(fields: Array[String]): Unit
> }
> {code}
> In addition we need Calcite rules to push a projection into a TableScan that
> refers to a {{ProjectableTableSource}}. We might need to tweak the cost model
> as well to push the optimizer in the right direction.
> Moreover, the {{CsvTableSource}} could be extended to implement
> {{ProjectableTableSource}}.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
