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https://issues.apache.org/jira/browse/HBASE-1136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12665298#action_12665298
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Jonathan Ellis commented on HBASE-1136:
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oh, I see what is going on. it's a bad test.
Key key = new StringKey("toto");
Key k2 = new StringKey("lulu");
Key k3 = new StringKey("mama");
bf.add(key);
bf.add(k2);
bf.add(k3);
assertTrue(bf.membershipTest(key));
assertTrue(bf.membershipTest(new StringKey("graknyl")));
graknyl was never added. it's relying on the implementation details of the old
(broken) HashFunction.
do you want me to just rip stuff like that out?
> HashFunction inadvertently destroys some randomness
> ---------------------------------------------------
>
> Key: HBASE-1136
> URL: https://issues.apache.org/jira/browse/HBASE-1136
> Project: Hadoop HBase
> Issue Type: Bug
> Reporter: Jonathan Ellis
> Fix For: 0.20.0
>
> Attachments: hash.patch
>
>
> the code
> for (int i = 0, initval = 0; i < nbHash; i++) {
> initval = result[i] = Math.abs(hashFunction.hash(b, initval) %
> maxValue);
> }
> restricts initval for the next hash to the [0, maxValue) range of the hash
> indexes returned. This is suboptimal, particularly for larger nbHash and
> smaller maxValue. Instead, use:
> for (int i = 0, initval = 0; i < nbHash; i++) {
> initval = hashFunction.hash(b, initval);
> result[i] = Math.abs(initval) % maxValue;
> }
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