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https://issues.apache.org/jira/browse/HDFS-7056?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14334515#comment-14334515
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Konstantin Shvachko commented on HDFS-7056:
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Sounds right, Jing. Let me write it down to make sure my math is right this
time.
{{binarySearch(diffs, snapshotId)}} returns {{i == -insertPoint-1}}, where
{{insertPoint}} is the index of the first element greater than the key. So if
the {{snapshotId}} is not found then we can start searching backwards from
{{insertPoint-1 == -i-2}}.
So we've been checking two extra elements. Good catch, thanks. Will create a
jira to fix this.
> Snapshot support for truncate
> -----------------------------
>
> Key: HDFS-7056
> URL: https://issues.apache.org/jira/browse/HDFS-7056
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: 3.0.0
> Reporter: Konstantin Shvachko
> Assignee: Plamen Jeliazkov
> Fix For: 2.7.0
>
> Attachments: HDFS-3107-HDFS-7056-combined-13.patch,
> HDFS-3107-HDFS-7056-combined-15.patch, HDFS-3107-HDFS-7056-combined.patch,
> HDFS-3107-HDFS-7056-combined.patch, HDFS-3107-HDFS-7056-combined.patch,
> HDFS-3107-HDFS-7056-combined.patch, HDFS-3107-HDFS-7056-combined.patch,
> HDFS-3107-HDFS-7056-combined.patch, HDFS-3107-HDFS-7056-combined.patch,
> HDFS-3107-HDFS-7056-combined.patch, HDFS-3107-HDFS-7056-combined.patch,
> HDFS-7056-13.patch, HDFS-7056-15.patch, HDFS-7056.15_branch2.patch,
> HDFS-7056.patch, HDFS-7056.patch, HDFS-7056.patch, HDFS-7056.patch,
> HDFS-7056.patch, HDFS-7056.patch, HDFS-7056.patch, HDFS-7056.patch,
> HDFSSnapshotWithTruncateDesign.docx, HDFSSnapshotWithTruncateDesign.docx,
> editsStored, editsStored.xml
>
>
> Implementation of truncate in HDFS-3107 does not allow truncating files which
> are in a snapshot. It is desirable to be able to truncate and still keep the
> old file state of the file in the snapshot.
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