[jira] [Created] (IOTDB-523) A potential query optimization for querying many measurements of a device

["Xiangdong Huang (Jira)" <ji...@apache.org>]

Xiangdong Huang created IOTDB-523:
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             Summary: A potential query optimization for querying many measurements of a device
                 Key: IOTDB-523
                 URL: https://issues.apache.org/jira/browse/IOTDB-523
             Project: Apache IoTDB
          Issue Type: Improvement
          Components: Core/Engine
            Reporter: Xiangdong Huang


Hi,

Today when I run a SQL like `select * from root` and enable the debug log on server, I find so many DeviceMetaData and ChunkMetadata are read.

Considering that in TsFile, a device's multiply chunk data will be stored together, is that possible to have the following optimization?

If a user query many measurements (e.g., select *  from, or select more than 1/2 measurements of a device), maybe there is no need to read the ChunkMeatadata... because if we find a ChunkGroup, if one column is needed to be read, other columns are high probability to be read.

I am not sure whether my idea is correct. Please leave your opinions.

 

 



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