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https://issues.apache.org/jira/browse/FLINK-5315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16602161#comment-16602161
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ASF GitHub Bot commented on FLINK-5315:
---------------------------------------
hequn8128 commented on a change in pull request #6521: [FLINK-5315][table]
Adding support for distinct operation for table API on DataStream
URL: https://github.com/apache/flink/pull/6521#discussion_r214681480
##########
File path:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/scala/expressionDsl.scala
##########
@@ -214,10 +214,25 @@ trait ImplicitExpressionOperations {
def varSamp = VarSamp(expr)
/**
- * Returns multiset aggregate of a given expression.
+ * Returns multiset aggregate of a given expression.
*/
def collect = Collect(expr)
+ /**
+ * Returns a distinct field reference to a given expression
+ */
+ def distinct: Expression = {
Review comment:
Hi @walterddr , I guess what fabian means is putting this function in
`org.apache.flink.table.expressions.Aggregation`, so that distinct can only be
called by an aggregate. In this way, we can even remove the test cases such as
`testDistinctOnNonAggregateExpression` since compile error will be thrown
directly by the IDE. What do you think?
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> Support distinct aggregations in table api
> ------------------------------------------
>
> Key: FLINK-5315
> URL: https://issues.apache.org/jira/browse/FLINK-5315
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Kurt Young
> Assignee: Rong Rong
> Priority: Major
> Labels: pull-request-available
>
> Support distinct aggregations in Table API in the following format:
> For Expressions:
> {code:scala}
> 'a.count.distinct // Expressions distinct modifier
> {code}
> For User-defined Function:
> {code:scala}
> singleArgUdaggFunc.distinct('a) // FunctionCall distinct modifier
> multiArgUdaggFunc.distinct('a, 'b) // FunctionCall distinct modifier
> {code}
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