[
https://issues.apache.org/jira/browse/FLINK-15497?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Kurt Young updated FLINK-15497:
-------------------------------
Description:
As we described in the doc:
[https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/table/sql.html#top-n]
when rank number is not required, we can reduce some output, like unnecessary
retract messages.
Here is an example which can re-produce:
{code:java}
val data = List(
("aaa", 97.0, 200.0),
("bbb", 67.0, 200.0),
("bbb", 162.0, 200.0)
)
val ds = failingDataSource(data).toTable(tEnv, 'guid, 'a, 'b)
tEnv.registerTable("T", ds)
val aggreagtedTable = tEnv.sqlQuery(
"""
|select guid,
| sum(a) as reached_score,
| sum(b) as max_score,
| sum(a) / sum(b) as score
|from T group by guid
|""".stripMargin
)
tEnv.registerTable("T2", aggreagtedTable)
val sql =
"""
|SELECT guid, reached_score, max_score, score
|FROM (
| SELECT *,
| ROW_NUMBER() OVER (ORDER BY score DESC) as rank_num
| FROM T2)
|WHERE rank_num <= 5
""".stripMargin
val sink = new TestingRetractSink
tEnv.sqlQuery(sql).toRetractStream[Row].addSink(sink).setParallelism(1)
env.execute()
{code}
In this case, the output is:
{code:java}
(true,aaa,97.0,200.0,0.485)
(true,bbb,67.0,200.0,0.335)
(false,bbb,67.0,200.0,0.335)
(true,bbb,229.0,400.0,0.5725)
(false,aaa,97.0,200.0,0.485)
(true,aaa,97.0,200.0,0.485)
{code}
But the last 2 messages are unnecessary.
> Streaming TopN operator doesn't reduce outputs when rank number is not
> required
> --------------------------------------------------------------------------------
>
> Key: FLINK-15497
> URL: https://issues.apache.org/jira/browse/FLINK-15497
> Project: Flink
> Issue Type: Bug
> Reporter: Kurt Young
> Priority: Major
>
> As we described in the doc:
> [https://ci.apache.org/projects/flink/flink-docs-release-1.9/dev/table/sql.html#top-n]
> when rank number is not required, we can reduce some output, like unnecessary
> retract messages.
> Here is an example which can re-produce:
> {code:java}
> val data = List(
> ("aaa", 97.0, 200.0),
> ("bbb", 67.0, 200.0),
> ("bbb", 162.0, 200.0)
> )
> val ds = failingDataSource(data).toTable(tEnv, 'guid, 'a, 'b)
> tEnv.registerTable("T", ds)
> val aggreagtedTable = tEnv.sqlQuery(
> """
> |select guid,
> | sum(a) as reached_score,
> | sum(b) as max_score,
> | sum(a) / sum(b) as score
> |from T group by guid
> |""".stripMargin
> )
> tEnv.registerTable("T2", aggreagtedTable)
> val sql =
> """
> |SELECT guid, reached_score, max_score, score
> |FROM (
> | SELECT *,
> | ROW_NUMBER() OVER (ORDER BY score DESC) as rank_num
> | FROM T2)
> |WHERE rank_num <= 5
> """.stripMargin
> val sink = new TestingRetractSink
> tEnv.sqlQuery(sql).toRetractStream[Row].addSink(sink).setParallelism(1)
> env.execute()
> {code}
> In this case, the output is:
> {code:java}
> (true,aaa,97.0,200.0,0.485)
> (true,bbb,67.0,200.0,0.335)
> (false,bbb,67.0,200.0,0.335)
> (true,bbb,229.0,400.0,0.5725)
> (false,aaa,97.0,200.0,0.485)
> (true,aaa,97.0,200.0,0.485)
> {code}
> But the last 2 messages are unnecessary.
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