Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2961#discussion_r91691224
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/table.scala
---
@@ -881,24 +883,21 @@ class GroupWindowedTable(
* }}}
*/
def select(fields: Expression*): Table = {
--- End diff --
Watermarks and timestamps should not be affected by this change. They are
treated as metadata by Flink and not part of the schema. Also watermarks and
timestamps should be assigned before the query. We do not support assigning
watermarks within a query.
I also had a quick look into it. One problem I found was that a window
alias is handled as an `UnresolvedFieldReference` in `select` here and
therefore added to the projection. However, the input does to have a field like
that and validation fails.
During validation, the window alias is correctly recognized. Maybe it makes
more sense to add the projection at this point by injection an additional
`Project` with the `RelBuilder`. Another solution could be a `RelOptRule`.
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