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https://issues.apache.org/jira/browse/HBASE-14283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14909071#comment-14909071
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Matteo Bertozzi commented on HBASE-14283:
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I was making the point for a 2/3.x just because, people was already scared by
the name v4 for the format. even if there are no real changes to the format
itself aside few things. also we had already an "incompatibile" change in a
minor version of hfile (the reason the minor version was introduced) and it was
more or less the same thing as this one. In that case was adding a field to the
header for checksum HBASE-5074.
in any case i'm pretty sure we can get the changes in a 1.x too. off by default
and people can decide if they care about that or not. more or less the same
thing happened for the hfile v2.1 (checksum), v2.2 (protobufs) and v3 (tags).
but that's not my call, the next RM for 1.3 will make the call. but you have a
+1 for me to change the hfile format in 2.0
> Reverse scan doesn’t work with HFile inline index/bloom blocks
> --------------------------------------------------------------
>
> Key: HBASE-14283
> URL: https://issues.apache.org/jira/browse/HBASE-14283
> Project: HBase
> Issue Type: Bug
> Reporter: Ben Lau
> Assignee: Ben Lau
> Attachments: HBASE-14283-v2.patch, HBASE-14283.patch,
> hfile-seek-before.patch
>
>
> Reverse scans do not work if an HFile contains inline bloom blocks or leaf
> level index blocks. The reason is because the seekBefore() call calculates
> the previous data block’s size by assuming data blocks are contiguous which
> is not the case in HFile V2 and beyond.
> Attached is a first cut patch (targeting
> bcef28eefaf192b0ad48c8011f98b8e944340da5 on trunk) which includes:
> (1) a unit test which exposes the bug and demonstrates failures for both
> inline bloom blocks and inline index blocks
> (2) a proposed fix for inline index blocks that does not require a new HFile
> version change, but is only performant for 1 and 2-level indexes and not 3+.
> 3+ requires an HFile format update for optimal performance.
> This patch does not fix the bloom filter blocks bug. But the fix should be
> similar to the case of inline index blocks. The reason I haven’t made the
> change yet is I want to confirm that you guys would be fine with me revising
> the HFile.Reader interface.
> Specifically, these 2 functions (getGeneralBloomFilterMetadata and
> getDeleteBloomFilterMetadata) need to return the BloomFilter. Right now the
> HFileReader class doesn’t have a reference to the bloom filters (and hence
> their indices) and only constructs the IO streams and hence has no way to
> know where the bloom blocks are in the HFile. It seems that the HFile.Reader
> bloom method comments state that they “know nothing about how that metadata
> is structured” but I do not know if that is a requirement of the abstraction
> (why?) or just an incidental current property.
> We would like to do 3 things with community approval:
> (1) Update the HFile.Reader interface and implementation to contain and
> return BloomFilters directly rather than unstructured IO streams
> (2) Merge the fixes for index blocks and bloom blocks into open source
> (3) Create a new Jira ticket for open source HBase to add a ‘prevBlockSize’
> field in the block header in the next HFile version, so that seekBefore()
> calls can not only be correct but performant in all cases.
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