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Posted to issues@flink.apache.org by "Shengkai Fang (Jira)" <ji...@apache.org> on 2020/07/21 10:01:00 UTC
[jira] [Updated] (FLINK-16528) Support Limit push down for
streaming sources
[ https://issues.apache.org/jira/browse/FLINK-16528?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Shengkai Fang updated FLINK-16528:
----------------------------------
Attachment: PushProjectIntoTableSourceScanRule.java
> Support Limit push down for streaming sources
> ---------------------------------------------
>
> Key: FLINK-16528
> URL: https://issues.apache.org/jira/browse/FLINK-16528
> Project: Flink
> Issue Type: New Feature
> Components: Table SQL / Ecosystem, Table SQL / Planner
> Reporter: Jark Wu
> Priority: Major
> Labels: usability
> Fix For: 1.12.0
>
>
> Currently, a limit query {{SELECT * FROM kafka LIMIT 10}} will be translated into TopN operator and will scan the full data in the source. However, {{LIMIT}} is a very useful feature in SQL CLI to explore data in the source. It doesn't make sense it never stop.
> We can support such case in streaming mode (ignore the text format):
> {code}
> flink > SELECT * FROM kafka LIMIT 10;
> kafka_key | user_name | lang | created_at
> --------------------+-----------------+------+-------------------------
> 494227746231685121 | burncaniff | en | 2014-07-29 14:07:31.000
> 494227746214535169 | gu8tn | ja | 2014-07-29 14:07:31.000
> 494227746219126785 | pequitamedicen | es | 2014-07-29 14:07:31.000
> 494227746201931777 | josnyS | ht | 2014-07-29 14:07:31.000
> 494227746219110401 | Cafe510 | en | 2014-07-29 14:07:31.000
> 494227746210332673 | Da_JuanAnd_Only | en | 2014-07-29 14:07:31.000
> 494227746193956865 | Smile_Kidrauhl6 | pt | 2014-07-29 14:07:31.000
> 494227750426017793 | CashforeverCD | en | 2014-07-29 14:07:32.000
> 494227750396653569 | FilmArsivimiz | tr | 2014-07-29 14:07:32.000
> 494227750388256769 | jmolas | es | 2014-07-29 14:07:32.000
> (10 rows)
> {code}
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