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John Sichi commented on HIVE-1721: ---------------------------------- Standard practice is to add new conf parameters, with sensible defaults, but including a way to disable the feature completely (and make that the default until we have sufficient confidence in it). > 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. -- This message is automatically generated by JIRA. For more information on JIRA, see: http://www.atlassian.com/software/jira