Github user jackylk commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/2323#discussion_r189477676
--- Diff: docs/datamap/bloomfilter-datamap-guide.md ---
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+# CarbonData BloomFilter DataMap (Alpha feature in 1.4.0)
+
+* [DataMap Management](#datamap-management)
+* [BloomFilter Datamap Introduction](#bloomfilter-datamap-introduction)
+* [Loading Data](#loading-data)
+* [Querying Data](#querying-data)
+* [Data Management](#data-management-with-bloomfilter-datamap)
+
+#### DataMap Management
+Creating BloomFilter DataMap
+ ```
+ CREATE DATAMAP [IF NOT EXISTS] datamap_name
+ ON TABLE main_table
+ USING 'bloomfilter'
+ DMPROPERTIES ('index_columns'='city, name', 'BLOOM_SIZE'='640000', 'BLOOM_FPP'='0.00001')
+ ```
+
+Dropping specified datamap
+ ```
+ DROP DATAMAP [IF EXISTS] datamap_name
+ ON TABLE main_table
+ ```
+
+Showing all DataMaps on this table
+ ```
+ SHOW DATAMAP
+ ON TABLE main_table
+ ```
+It will show all DataMaps created on main table.
+
+
+## BloomFilter DataMap Introduction
+A Bloom filter is a space-efficient probabilistic data structure that is used to test whether an element is a member of a set.
+Carbondata introduce BloomFilter as an index datamap to enhance the performance of querying with precise value.
+Internally, CarbonData maintains a BloomFilter per blocklet for each index column to indicate that whether a value of the column is in this blocklet.
--- End diff --
Please give a hint what the suitable scenario it is to use this datamap, for example, for queries that do precise match on high cardinality column
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Locked
