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https://issues.apache.org/jira/browse/HIVE-1721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13061038#comment-13061038
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J. Andrew Key commented on HIVE-1721:
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I may use org.apache.hadoop.util.bloom.BloomFilter
http://svn.apache.org/repos/asf/hadoop/common/trunk/common/src/java/org/apache/hadoop/util/bloom/BloomFilter.java.
Should there be a query syntax for controlling the creation of the bloom filter
with options such as:
1. vector size, hash function type and number?
2. expected table size and acceptable level of false positives?
If anyone has any preference or ideas, please share them.
> use bloom filters to improve the performance of joins
> -----------------------------------------------------
>
> Key: HIVE-1721
> URL: https://issues.apache.org/jira/browse/HIVE-1721
> Project: Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: J. Andrew Key
> Labels: optimization
>
> In case of map-joins, it is likely that the big table will not find many
> matching rows from the small table.
> Currently, we perform a hash-map lookup for every row in the big table, which
> can be pretty expensive.
> It might be useful to try out a bloom-filter containing all the elements in
> the small table.
> Each element from the big table is first searched in the bloom filter, and
> only in case of a positive match,
> the small table hash table is explored.
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