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https://issues.apache.org/jira/browse/HADOOP-3063?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12655793#action_12655793
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stack commented on HADOOP-3063:
-------------------------------
Reviewing the patch, it looks great. The above failure would seem to be
because the last two arguments need to be flipped:
{code}
236 + bloomFilter = new DynamicBloomFilter(vectorSize, HASH_COUNT,
numKeys,
237 + Hash.getHashType(conf));
{code}
....the DBF constructor looks like this:
{code}
1528 + public DynamicBloomFilter(int vectorSize, int nbHash, int hashType, int
nr) {
{code}
Test still fails with an assertion error so maybe the above is not right.
There is an hbasism still in the code that you probably want to remove:
{code}
408 + String name = conf.get("hbase.hash.type", "murmur");
{code}
> BloomMapFile - fail-fast version of MapFile for sparsely populated key space
> ----------------------------------------------------------------------------
>
> Key: HADOOP-3063
> URL: https://issues.apache.org/jira/browse/HADOOP-3063
> Project: Hadoop Core
> Issue Type: Improvement
> Components: io
> Affects Versions: 0.20.0
> Reporter: Andrzej Bialecki
> Fix For: 0.20.0
>
> Attachments: bloommap-v2.patch, bloommap-v3.patch, bloommap.patch
>
>
> The need for this improvement arose when working with large ancillary
> MapFile-s (essentially used as external dictionaries). For each invokation of
> map() / reduce() it was necessary to perform several look-ups in these
> MapFile-s, and in case of sparsely populated key-space the cost of finding
> that a key is absent was too high.
> This patch implements a subclass of MapFile that creates a Bloom filter from
> all keys, so that accurate tests for absence of keys can be performed quickly
> and with 100% accuracy.
> Writer.append() operations update a DynamicBloomFilter, which is then
> serialized when the Writer is closed. This filter is loaded in memory when a
> Reader is created. Reader.get() operation first checks the filter for the key
> membership, and if the key is absent it immediately returns null without
> doing any further IO.
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