[jira] [Created] (IOTDB-586) [Distributed] Eliminate some timeseries schemas When memory is limited

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

WangChao created IOTDB-586:
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             Summary: [Distributed] Eliminate some timeseries schemas When memory is limited
                 Key: IOTDB-586
                 URL: https://issues.apache.org/jira/browse/IOTDB-586
             Project: Apache IoTDB
          Issue Type: Improvement
          Components: Core/Engine
            Reporter: WangChao


Some businesses have 400 million time series. It will be very memory consuming to stored all of them. We need to eliminate some unusual time series schemas.

 

The possible way is,

1. The time sequence pulled from the remote is stored in a new MTREE. The retrieval can retrieve two mtrees at the same time, and only this remote MTREE will be eliminated

2. All schemas exist in one MTREE. Scan the whole MTREE  to find the remote schema for elimination

 

There are also two ways to elimination:

1. Direct discard

2. Save to local file

 

When does it need to be eliminated?

1. Limit the number of time series of an MTREE,  exceeding that of elimination

2. Limit memory usage of MTREE (for example, 500MB), which will be eliminated if exceeded

 


I tend to maintain one MTREE, discard it directly, and limit the number of time series of MTREE.

The advantages are:

1. Under normal circumstances, it takes less time to read metadata from the remote memory than from the disk randomly. If it is loaded from the disk, it means that the memory is full, and it needs to eliminate other schemas when reading from the disk, which is troublesome

2. Query performance may be poor when maintain two MTree

3. It is easy to maintain the number of time series

 

Please leave your opinions.



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