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liaolanyu commented on IOTDB-5522: ---------------------------------- This doc describes what we think may slow down the last query: [https://apache-iotdb.feishu.cn/docx/GVe2d35aAoVYVhxnueac0hK9nUf] However, we found current last query might behave wrongly if multiple DataRegions of one timeseries exists on one DataNode. > Last Query performance improvement > ---------------------------------- > > Key: IOTDB-5522 > URL: https://issues.apache.org/jira/browse/IOTDB-5522 > Project: Apache IoTDB > Issue Type: Improvement > Components: Core/Query > Reporter: Yuan Tian > Assignee: liaolanyu > Priority: Major > Attachments: image-2023-02-10-21-23-28-478.png, > image-2023-02-16-20-16-11-215.png > > > If we have a lot of data regions and then we execute `select last s1 from > root.sg.d1`, this sql may not execute that fast as we expected, because it > may need to wait for all data regions' result and then merge it. > In some user's case, we build a 1C9D cluster, we set dataregion per database > to 27. We need 300ms to get the last query result which even slower than > MatrixDB. > !image-2023-02-16-20-16-11-215.png! -- This message was sent by Atlassian Jira (v8.20.10#820010)