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https://issues.apache.org/jira/browse/HBASE-20795?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16524241#comment-16524241
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stack commented on HBASE-20795:
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[[email protected]] Thanks.
How'd you arrive at the need for this fix?
Was it code reading?
Or did you see a perf difference?
You saw the comment on the BBKVC class which says: "This is a tricked-out
Comparator at heart of hbase read and write. It is in the HOT path so we try
all sorts of ugly stuff so we can go faster. See below in this javadoc comment
for the list."
I did a bunch of work trying to minimize the bytecode these methods generate as
they are the hottest code paths in our code base -- small differences here show
at the macro scale. This fix adds code. At one stage I'd duplicated the code
here into CellComparatorImpl trying to make it so we minimize the Cell types
that traverse this code path. Perhaps we should do that again? I'm still
profiling. Let me add this in for now and if it causes slowdown, I'll dupe the
method. Thanks.
> Allow option in BBKVComparator.compare to do comparison without sequence id
> ---------------------------------------------------------------------------
>
> Key: HBASE-20795
> URL: https://issues.apache.org/jira/browse/HBASE-20795
> Project: HBase
> Issue Type: Bug
> Affects Versions: 2.0.1
> Reporter: Ankit Singhal
> Assignee: Ankit Singhal
> Priority: Major
> Attachments: HBASE-20795.patch
>
>
> CellComparatorImpl#compare(final Cell a, final Cell b, boolean
> ignoreSequenceid) needs to ignore sequence id in comparison if
> ignoreSequenceId parameter is set to true but BBKVComparator.compare used
> internally for the cell of type ByteBufferKeyValue doesn't consider this.
> {code}
> @Override
> public int compare(final Cell a, final Cell b, boolean ignoreSequenceid) {
> int diff = 0;
> // "Peel off" the most common path.
> if (a instanceof ByteBufferKeyValue && b instanceof ByteBufferKeyValue) {
> diff = BBKVComparator.compare((ByteBufferKeyValue)a,
> (ByteBufferKeyValue)b);
> if (diff != 0) {
> return diff;
> }
> } else {
> diff = compareRows(a, b);
> if (diff != 0) {
> return diff;
> }
> diff = compareWithoutRow(a, b);
> if (diff != 0) {
> return diff;
> }
> }
> // Negate following comparisons so later edits show up first mvccVersion:
> later sorts first
> return ignoreSequenceid? diff: Long.compare(b.getSequenceId(),
> a.getSequenceId());
> }
> {code}
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