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From "Fabian Hueske (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9528) Incorrect results: Filter does not treat Upsert messages correctly.
Date Thu, 14 Jun 2018 14:23:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9528?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16512534#comment-16512534
] 

Fabian Hueske commented on FLINK-9528:
--------------------------------------

I don't think we need state in all Filters working under AccMode.
 Consider the following plan:
{code:java}
A -> GroupAgg(groupBy x, count(*) AS y) -> Filter(y < 10) -\
                                                            Join(A.x = B.x)
B ---------------------------------------------------------/
{code}
The Filter could work in AccMode (because the aggregation and join work on the same key).
However, adding state to the filter would be unnecessary because the Join would automatically
do the deduplication and also the messaging overhead wouldn't be too high because messages
would not go over the network.

I'm quite sure this is true for all other internal AccMode connections except for the Sink
case.
That's why I'm proposing to add the state to the sink instead of the filter as it seems to
be the only case that would need the additional state.

> Incorrect results: Filter does not treat Upsert messages correctly.
> -------------------------------------------------------------------
>
>                 Key: FLINK-9528
>                 URL: https://issues.apache.org/jira/browse/FLINK-9528
>             Project: Flink
>          Issue Type: Bug
>          Components: Table API &amp; SQL
>    Affects Versions: 1.3.3, 1.5.0, 1.4.2
>            Reporter: Fabian Hueske
>            Assignee: Hequn Cheng
>            Priority: Critical
>
> Currently, Filters (i.e., Calcs with predicates) do not distinguish between retraction
and upsert mode. A Calc looks at record (regardless of its update semantics) and either discard
it (predicate evaluates to false) or pass it on (predicate evaluates to true).
> This works fine for messages with retraction semantics but is not correct for upsert
messages.
> The following test case (can be pasted into {{TableSinkITCase}}) shows the problem:
> {code:java}
>   @Test
>   def testUpsertsWithFilter(): Unit = {
>     val env = StreamExecutionEnvironment.getExecutionEnvironment
>     env.getConfig.enableObjectReuse()
>     env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
>     val tEnv = TableEnvironment.getTableEnvironment(env)
>     val t = StreamTestData.get3TupleDataStream(env)
>       .assignAscendingTimestamps(_._1.toLong)
>       .toTable(tEnv, 'id, 'num, 'text)
>     t.select('text.charLength() as 'len)
>       .groupBy('len)
>       .select('len, 'len.count as 'cnt)
>       // .where('cnt < 7)
>       .writeToSink(new TestUpsertSink(Array("len"), false))
>     env.execute()
>     val results = RowCollector.getAndClearValues
>     val retracted = RowCollector.upsertResults(results, Array(0)).sorted
>     val expectedWithoutFilter = List(
>       "2,1", "5,1", "9,9", "10,7", "11,1", "14,1", "25,1").sorted
>     val expectedWithFilter = List(
>     "2,1", "5,1", "11,1", "14,1", "25,1").sorted
>     assertEquals(expectedWithoutFilter, retracted)
>     // assertEquals(expectedWithFilter, retracted)
>   }
> {code}
> When we add a filter on the aggregation result, we would expect that all rows that do
not fulfill the condition are removed from the result. However, the filter only removes the
upsert message such that the previous version remains in the result.
> One solution could be to make a filter aware of the update semantics (retract or upsert)
and convert the upsert message into a delete message if the predicate evaluates to false.



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