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https://issues.apache.org/jira/browse/IOTDB-605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17096096#comment-17096096
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Zesong Sun commented on IOTDB-605:
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Here is the *final design*:
* Each node is consisted of *MetadataIndexEntry* list: [<device / measurement
name, offset, childNodeType>, ... ] and an *endOffset*. These elements
represent the children nodes of the internal node.
* The field childNodeType is an enum value, which represents the type of the
next child node.
* The degree of node *maxDegreeOfIndexNode* could be configured by users. (In
the examples, I set maxDegreeOfIndexNode = 10 for convenience, and default
value = 1024)
* The storage process is from bottom to up. Whenever the blocks >=
maxDegreeOfIndexNode, a parent level index will be generated and will be
insisted into disk.
* The query process is from top to bottom with binary search of the array.
> Add more levels of index in TsFileMetadata
> ------------------------------------------
>
> Key: IOTDB-605
> URL: https://issues.apache.org/jira/browse/IOTDB-605
> Project: Apache IoTDB
> Issue Type: Improvement
> Reporter: Zesong Sun
> Assignee: Zesong Sun
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.10.0-SNAPSHOT
>
> Attachments: Examples.png, Structure of MetadataIndex levels.png
>
>
> Facing a scenario that one device has 300k measurements, when we read one
> time series in a TsFile, we need to deserialize 300k TimeseriesMetadata,
> which costs about 250ms (just for reading metadata of one tsfile). This may
> cause the query much slow.
> As this scenario is not rare, I think this should be optimized by adding more
> indexes in TsFileMetadata.
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