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https://issues.apache.org/jira/browse/HBASE-4489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13125481#comment-13125481
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Dave Revell commented on HBASE-4489:
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@Nicolas,
In response to your #1:
> "If you want to save space, you should probably switch to a UINT32 for the
> key range instead of the current INT64. This should scale for up to 2 million
> regions."
Users can use whatever length of keys they want. RegionSplitter just chooses
the region boundaries, which has no effect on space consumption.
In response to your #2:
Every cryptographic hash function distributes its values uniformly across the
space of byte strings of length N. So that makes UniformSplit a sensible
default when using MD5 hashes or SHA1 hashes or whatever else, as long as
they're not converted to ASCII.
The goal here is sane default behavior that makes sense for typical use cases.
Evenly dividing the key space accomplishes that goal. At least that's *my* goal.
> Better key splitting in RegionSplitter
> --------------------------------------
>
> Key: HBASE-4489
> URL: https://issues.apache.org/jira/browse/HBASE-4489
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 0.90.4
> Reporter: Dave Revell
> Assignee: Dave Revell
> Attachments: HBASE-4489-branch0.90-v1.patch,
> HBASE-4489-branch0.90-v2.patch, HBASE-4489-branch0.90-v3.patch,
> HBASE-4489-trunk-v1.patch, HBASE-4489-trunk-v2.patch,
> HBASE-4489-trunk-v3.patch
>
>
> The RegionSplitter utility allows users to create a pre-split table from the
> command line or do a rolling split on an existing table. It supports
> pluggable split algorithms that implement the SplitAlgorithm interface. The
> only/default SplitAlgorithm is one that assumes keys fall in the range from
> ASCII string "00000000" to ASCII string "7FFFFFFF". This is not a sane
> default, and seems useless to most users. Users are likely to be surprised by
> the fact that all the region splits occur in in the byte range of ASCII
> characters.
> A better default split algorithm would be one that evenly divides the space
> of all bytes, which is what this patch does. Making a table with five regions
> would split at \x33\x33..., \x66\x66...., \x99\x99..., \xCC\xCC..., and
> \xFF\xFF.
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