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From "Gopal V (JIRA)" <>
Subject [jira] [Commented] (HIVE-9188) BloomFilter in ORC row group index
Date Thu, 08 Jan 2015 06:49:34 GMT


Gopal V commented on HIVE-9188:

Left some comments, particularly about the encoding of the bloom filter itself.

The List<Long> is a bad idea as the 2nd long in the list is actually a double containing
the fpp value.

Otherwise the patch looks good. I've added it to the build right now, will ETL in a bunch
of the NYC taxi data with this and run some point-scan queries.

> BloomFilter in ORC row group index
> ----------------------------------
>                 Key: HIVE-9188
>                 URL:
>             Project: Hive
>          Issue Type: New Feature
>          Components: File Formats
>    Affects Versions: 0.15.0
>            Reporter: Prasanth Jayachandran
>            Assignee: Prasanth Jayachandran
>              Labels: orcfile
>         Attachments: HIVE-9188.1.patch, HIVE-9188.2.patch, HIVE-9188.3.patch, HIVE-9188.4.patch
> BloomFilters are well known probabilistic data structure for set membership checking.
We can use bloom filters in ORC index for better row group pruning. Currently, ORC row group
index uses min/max statistics to eliminate row groups (stripes as well) that do not satisfy
predicate condition specified in the query. But in some cases, the efficiency of min/max based
elimination is not optimal (unsorted columns with wide range of entries). Bloom filters can
be an effective and efficient alternative for row group/split elimination for point queries
or queries with IN clause.

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