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https://issues.apache.org/jira/browse/HBASE-15400?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15182211#comment-15182211
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Clara Xiong commented on HBASE-15400:
-------------------------------------
Sorry if I didn't make it clear. If a user load a single bulkload file with
large time span to an empty store with seqId 0 or 1 or a very small number,
then call major compaction to output a date tiered layout. They use the default
window size and then we output files more than the existing seq id. Another
extreme case is a user use -1 for bulk load files by explicitly turning off the
configuration assign sequence id. One more extreme case is a user that specify
timestamp for business logic which cover an extremely large time range that
requires more output files than the seq id the first file gets written to an
empty store.
> Using Multiple Output for Date Tiered Compaction
> ------------------------------------------------
>
> Key: HBASE-15400
> URL: https://issues.apache.org/jira/browse/HBASE-15400
> Project: HBase
> Issue Type: Sub-task
> Components: Compaction
> Reporter: Clara Xiong
> Assignee: Clara Xiong
> Fix For: 2.0.0
>
> Attachments: HBASE-15400.patch
>
>
> When we compact, we can output multiple files along the current window
> boundaries. There are two use cases:
> 1. Major compaction: We want to output date tiered store files.
> 2. Bulk load files and the old file generated by major compaction before
> upgrading to DTCP.
> Pros:
> 1. Restore locality, process versioning, updates and deletes while
> maintaining the tiered layout.
> 2. The best way to fix a skewed layout.
>
> This work is based on a prototype of date tiered file writer from
> HBASE-15389. I have to call out a few design decisions:
> 1. We only want to output the files along all windows for major compaction.
> And we want to output multiple files older than max age in the sizes of the
> maximum tier window size determined by base window size, windows per tier and
> max age.
> 2. For minor compaction, we don't want to output too many files, which will
> remain around because of current restriction of contiguous compaction by seq
> id. I will only output two files if all the files in the windows are being
> combined, one for the data within window and the other for the out-of-window
> tail. If there is any file in the window excluded from compaction, only one
> file will be output from compaction. When the windows are promoted, the
> situation of out of order data will gradually improve.
> 3. We have to pass the boundaries with the list of store file as a complete
> time snapshot instead of two separate calls because window layout is
> determined by the time the computation is called. So we will need new type of
> compaction request.
> 4. Since we will assign the same seq id for all output files, we need to sort
> by maxTimestamp subsequently. Right now all compaction policy gets the files
> sorted for StoreFileManager which sorts by seq id and other criteria. I will
> use this order for DTCP only, to avoid impacting other compaction policies.
> 5. We need some cleanup of current design of StoreEngine and CompactionPolicy.
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