Github user akashrn5 commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/2215#discussion_r189507570
--- Diff: docs/datamap/lucene-datamap-guide.md ---
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+# CarbonData Lucene DataMap (Alpha feature in 1.4.0)
+
+* [DataMap Management](#datamap-management)
+* [Lucene Datamap](#lucene-datamap-introduction)
+* [Loading Data](#loading-data)
+* [Querying Data](#querying-data)
+* [Data Management](#data-management-with-pre-aggregate-tables)
+
+#### DataMap Management
+Lucene DataMap can be created using following DDL
+ ```
+ CREATE DATAMAP [IF NOT EXISTS] datamap_name
+ ON TABLE main_table
+ USING "lucene"
+ DMPROPERTIES ('index_columns'='city, name', ...)
+ ```
+
+DataMap can be dropped using following DDL:
+ ```
+ DROP DATAMAP [IF EXISTS] datamap_name
+ ON TABLE main_table
+ ```
+To show all DataMaps created, use:
+ ```
+ SHOW DATAMAP
+ ON TABLE main_table
+ ```
+It will show all DataMaps created on main table.
+
+
+## Lucene DataMap Introduction
+ Lucene is a high performance, full featured text search engine. Lucene
is integrated to carbon as
+ an index datamap and managed along with main tables by CarbonData.User
can create lucene datamap
+ to improve query performance on string columns which has content of more
length.
+
+ For instance, main table called **datamap_test** which is defined as:
+
+ ```
+ CREATE TABLE datamap_test (
+ name string,
+ age int,
+ city string,
+ country string)
+ STORED BY 'carbondata'
+ ```
+
+ User can create Lucene datamap using the Create DataMap DDL:
+
+ ```
+ CREATE DATAMAP dm
+ ON TABLE datamap_test
+ USING "lucene"
+ DMPROPERTIES ('INDEX_COLUMNS' = 'name, country')
+ ```
+
+## Loading data
+When loading data to main table, lucene index files will be generated for
all the
+index_columns(String Columns) given in DMProperties which contains
information about the data
+location of index_columns. These index files will be written inside a
folder named with datamap name
+inside each segment folders.
+
+A system level configuration carbon.lucene.compression.mode can be added
for best compression of
+lucene index files. The default value is speed, where the index writing
speed will be more. If the
+value is compression, the index file size will be compressed.
+
+## Querying data
+As a technique for query acceleration, Lucene indexes cannot be queried
directly.
+Queries are to be made on main table. when a query with
TEXT_MATCH('name:c10') or
+TEXT_MATCH_WITH_LIMIT('name:n10',10)[the second parameter represents the
number of result to be
+returned, if user does not specify this value, all results will be
returned without any limit] is
+fired, two jobs are fired.The first job writes the temporary files in
folder created at table level
+which contains lucene's seach results and these files will be read in
second job to give faster
+results. These temporary files will be cleared once the query finishes.
+
+User can verify whether a query can leverage Lucene datamap or not by
executing `EXPLAIN`
+command, which will show the transformed logical plan, and thus user can
check whether TEXT_MATCH()
+filter is applied on query or not.
+
+Note: The filter columns in TEXT_MATCH or TEXT_MATCH_WITH_LIMIT must be
always in lower case and
+filter condition like 'AND','OR' must be in upper case.
+
+Ex: ```
+ select * from datamap_test where TEXT_MATCH('name:*10 AND name:*n*')
+ ```
+
+Below like queries can be converted to text_match queries as following:
+```
+select * from datamap_test where name='n10'
+
+select * from datamap_test where name like 'n1%'
+
+select * from datamap_test where name like '%10'
+
+select * from datamap_test where name like '%n%'
+
+select * from datamap_test where name like '%10' and name not like '%n%'
+```
+Lucene TEXT_MATCH Queries:
+```
+select * from datamap_test where TEXT_MATCH('name:n10')
+
+select * from datamap_test where TEXT_MATCH('name:n1*')
+
+select * from datamap_test where TEXT_MATCH('name:*10')
+
+select * from datamap_test where TEXT_MATCH('name:*n*')
+
+select * from datamap_test where TEXT_MATCH('name:*10 -name:*n*')
--- End diff --
added a link, which will provide details of all these queries
---
