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https://issues.apache.org/jira/browse/FLINK-7696?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Fabian Hueske closed FLINK-7696.
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Resolution: Implemented
Fix Version/s: 1.4.0
Implemented for 1.4.0 with 9a2ba6e058e907aef65e0af8731ca5ec8733712e
> Add projection push-down support for TableSources with time attributes
> ----------------------------------------------------------------------
>
> Key: FLINK-7696
> URL: https://issues.apache.org/jira/browse/FLINK-7696
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Affects Versions: 1.4.0
> Reporter: Fabian Hueske
> Fix For: 1.4.0
>
>
> Table sources that implement the {{DefinedProctimeAttribute}} or
> {{DefinedRowtimeAttribute}} do not support projection push-down even if they
> also implement {{ProjectableTableSource}}.
> There are several problems:
> - the schema of a {{TableSource}} that implements {{DefinedRowtimeAttribute}}
> or {{DefinedProctimeAttribute}} is constructed in the catalog not in the
> {{TableSource}} (proctime fields are always appended at the end).
> - the {{ProjectableTableSource.projectFields()}} method returns the projected
> fields as int indicies. In order to handle the indicies correctly, the
> TableSource would need to know about the internals of the Table API.
> - {{ProjectableTableSource.projectFields()}} might reorder fields and move a
> proctime field into the middle of the schema. However, the TableSource has no
> control over that.
> - A {{TableSource}} that implements {{DefinedRowtimeAttribute}} or
> {{DefinedProctimeAttribute}} would need to change the return values of
> {{getRowtimeAttribute()}} or {{getProctimeAttribute()}} depending on whether
> the attribute is kept or not.
> Adjusting the schema of table sources inside of the Table API makes all of
> this quite messy. Maybe we need to refine the interfaces. For instance, we
> could ask users to explicitly add time indicator fields in the
> {{TypeInformation}} returned by {{TableSource.getReturnType()}}. However,
> that might collide with plans to add computable time attributes as proposed
> in FLINK-7548.
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