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https://issues.apache.org/jira/browse/IOTDB-862?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17189830#comment-17189830
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WangChao commented on IOTDB-862:
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Maybe we can make time range larger to minimize the influence of out-of-order?
like query the last 10s data, not the 5s when only need 5s.
> Register a time range (raw data/ down sampling) query template for monitoring
> applications
> ------------------------------------------------------------------------------------------
>
> Key: IOTDB-862
> URL: https://issues.apache.org/jira/browse/IOTDB-862
> Project: Apache IoTDB
> Issue Type: New Feature
> Components: Core/Engine
> Reporter: Jialin Qiao
> Priority: Major
>
> In monitoring scenarios, the query pattern is constant, only the time range
> predicate varies. What's more, the time range is in monotone increasing.
> For example, someone uses Grafana to visualize a time series for the last 5
> minutes and refresh the web page per 5s. Then, for each query instance, IoTDB
> receives a query like "select s1 from root.sg.d1 where time >= T2-5m and time
> <=T2". And the next query instance is "select s1 from root.sg.d1 where time
> >= T2+5s-5m and time <=T2+5s"
> We can see that there are many overlapped data between the two query
> instances.
> So, if we can cache the result of the first query, then, data of 4m55s could
> be reused for the next query.
>
> The idea is:
> (1) let users register such query templates (only time range condition can be
> changed)
> (2) cache the result data of the query
> (3) for each query, read the data in the cache, and load the left data on
> disk.
> (4) discard the outdated data in the cache
> (5) we suppose users can bear some out-of-order data not be visualized on
> Grafana
>
> User interface:
> (1) a sql to register/drop query templates
> (2) a new keyword to claim that a query uses the template
> (3) users can set the cache size in iotdb-engine.properties
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