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From ravipes...@apache.org
Subject [45/50] [abbrv] carbondata git commit: [CARBONDATA-1702] [Segment-Reading] added doc for query from specified segments feature
Date Tue, 09 Jan 2018 04:02:13 GMT
[CARBONDATA-1702] [Segment-Reading] added doc for query from specified segments feature

add doc for query from specified segments

This closes #1727


Project: http://git-wip-us.apache.org/repos/asf/carbondata/repo
Commit: http://git-wip-us.apache.org/repos/asf/carbondata/commit/705b1111
Tree: http://git-wip-us.apache.org/repos/asf/carbondata/tree/705b1111
Diff: http://git-wip-us.apache.org/repos/asf/carbondata/diff/705b1111

Branch: refs/heads/branch-1.3
Commit: 705b1111de1e84f1bebb86b6550fcfed477e6d63
Parents: c70e73f
Author: praveenmeenakshi56 <praveenmeenakshi56@gmail.com>
Authored: Wed Dec 27 19:30:52 2017 +0530
Committer: chenliang613 <chenliang613@huawei.com>
Committed: Mon Jan 8 15:11:05 2018 +0800

----------------------------------------------------------------------
 docs/data-management-on-carbondata.md | 79 ++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/carbondata/blob/705b1111/docs/data-management-on-carbondata.md
----------------------------------------------------------------------
diff --git a/docs/data-management-on-carbondata.md b/docs/data-management-on-carbondata.md
index 20c70e3..39acfbf 100644
--- a/docs/data-management-on-carbondata.md
+++ b/docs/data-management-on-carbondata.md
@@ -781,3 +781,82 @@ This tutorial is going to introduce all commands and data operations
on CarbonDa
   ```
   DELETE FROM TABLE CarbonDatabase.CarbonTable WHERE SEGMENT.STARTTIME BEFORE '2017-06-01
12:05:06' 
   ```
+### SEGMENT READING
+
+  This command is used to read data from specified segments during CarbonScan.
+  
+  
+  Get the Segment ID:
+  
+  ```
+  SHOW SEGMENTS FOR TABLE [db_name.]table_name LIMIT number_of_segments
+  ```
+  
+  Set the segment IDs
+  
+  ```
+  SET cabon.input.segments.<database_name>.<table_name> = <list of segment
IDs>;
+  ```
+  
+  **Property:**
+  
+  cabon.input.segments:  Specifies the segment IDs to be queried. This property allows you
to query specified segments of the specified table. The CarbonScan will read data from specified
segments only.
+  
+  ```
+  SET cabon.input.segments.<database_name>.<table_name> = <list of segment
IDs>;
+  ```
+  
+  If user wants to query with segments reading in multi threading mode, then CarbonSession.threadSet
can be used instead of SET query.
+  
+  ```
+  CarbonSession.threadSet ("cabon.input.segments.<database_name>.<table_name>","<list
of segment IDs>");
+  ```
+  
+  Reset the segment IDs:
+  
+  ```
+  SET cabon.input.segments.<database_name>.<table_name> = *;
+  ```
+  
+  If user wants to query with segments reading in multi threading mode, then CarbonSession.threadSet
can be used instead of SET query. 
+  
+  ```
+  CarbonSession.threadSet ("cabon.input.segments.<database_name>.<table_name>","*");
+  ```
+  
+  Reset
+  
+  It will reset all the properties set for carbondata. It is not recommended if you do not
want to reset all the properties except cabon.input.segments.
+  
+  ```
+  RESET
+  ```
+  
+  **NOTE**: It is not recommended to set this property in carbon.properties file, because
all the sessions will take this segments list unless it is overwritten at session or thread
level.
+  
+  **Examples:**
+  
+  * Example to show the list of segment IDs,segment status, and other required details and
then specify the list of segments to be read.
+  
+  ```
+  SHOW SEGMENTS FOR carbontable1;
+  
+  SET cabon.input.segments.db.carbontable1 = 1,3,9;
+  ```
+  
+  * Example to query with segments reading in multi threading mode:
+  
+  ```
+  CarbonSession.threadSet ("cabon.input.segments.db.carbontable_Multi_Thread","1,3");
+  ```
+  
+  * Example for threadset in multithread environment (following shows how it is used in Scala
code):
+  
+  ```
+  def main(args: Array[String]) {
+  Future {          
+    CarbonSession.threadSet ("cabon.input.segments.db.carbontable_Multi_Thread","1")
+    spark.sql("select count(empno) from cabon.input.segments.db.carbontable_Multi_Thread").show();
+     }
+   }
+  ```


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