Github user kumarvishal09 commented on a diff in the pull request:

    https://github.com/apache/carbondata/pull/1886#discussion_r165641742
  
    --- Diff: docs/data-management-on-carbondata.md ---
    @@ -748,6 +749,250 @@ This tutorial is going to introduce all commands and 
data operations on CarbonDa
       * The partitioned column can be excluded from SORT_COLUMNS, this will 
let other columns to do the efficient sorting.
       * When writing SQL on a partition table, try to use filters on the 
partition column.
     
    +## PRE-AGGREGATE TABLES
    +  Carbondata supports pre aggregating of data so that OLAP kind of queries 
can fetch data 
    +  much faster.Aggregate tables are created as datamaps so that the 
handling is as efficient as 
    +  other indexing support.Users can create as many aggregate tables they 
require as datamaps to 
    +  improve their query performance,provided the storage requirements and 
loading speeds are 
    +  acceptable.
    +  
    +  For main table called **sales** which is defined as 
    +  
    +  ```
    +  CREATE TABLE sales (
    +  order_time timestamp,
    +  user_id string,
    +  sex string,
    +  country string,
    +  quantity int,
    +  price bigint)
    +  STORED BY 'carbondata'
    +  ```
    +  
    +  user can create pre-aggregate tables using the DDL
    +  
    +  ```
    +  CREATE DATAMAP agg_sales
    +  ON TABLE sales
    +  USING "preaggregate"
    +  AS
    +  SELECT country, sex, sum(quantity), avg(price)
    +  FROM sales
    +  GROUP BY country, sex
    +  ```
    +  
    +<b><p align="left">Functions supported in pre-aggregate tables</p></b>
    +
    +| Function | Rollup supported |
    +|-----------|----------------|
    +| SUM | Yes |
    +| AVG | Yes |
    +| MAX | Yes |
    +| MIN | Yes |
    +| COUNT | Yes |
    +| DISTINCT COUNT | No |
    --- End diff --
    
    Currently we are not supporting distinct count and in future only for 
timeseries we can support


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