[GitHub] kkhatua opened a new pull request #1593: DRILL-6050: Provide a limit to number of rows fetched for a query in UI

[GitBox <gi...@apache.org>]

kkhatua opened a new pull request #1593: DRILL-6050: Provide a limit to number of rows fetched for a query in UI
URL: https://github.com/apache/drill/pull/1593
 
 
   Currently, the WebServer side needs to process the entire set of results and stream it back to the WebClient, which puts immense pressure on the WebServer when rendering the resultset. 
   
   Since the WebUI does paginate results, we can load a larger set for pagination on the browser client and relieve pressure off the WebServer to host all the data (most of which will never be streamed to the browser).
   e.g. Fetching all rows from a 1Billion records table is impractical and can be capped at (say) 1K. Currently, the user has to explicitly specify LIMIT in the submitted query. 
   
   An option is provided in the field to allow for this entry, and can be set to selected by default for the Web UI.
   The submitted query indicates that an auto-limiting wrapper was applied.
   In addition, the resultset is now configurable to allow for the default number or rows displayed per page to be changed from 10 to anything that the user might want.
   
   Configuration additions in `drill-module.conf` (changes should be made in `drill-override.conf` ):
   ```
   drill.exec.http: {
       web.client.resultset: {
           autolimit {
               enable: true,
               rows: 1000
           },
           defaultRowsPerPage: 10
       }
   }
   ```
   
   Screenshot with default (unselected) set to limit of 23:
   ![image](https://user-images.githubusercontent.com/4335237/50617613-ffc37080-0ea2-11e9-8840-4dc03c4dd58f.png)
   
   Screenshot with default rows per page changed to 12.
   ![image](https://user-images.githubusercontent.com/4335237/50617643-1b2e7b80-0ea3-11e9-8efe-ab789a05f36e.png)
   
   Screenshot of the profile indicates the auto-limit having been applied:
   ![image](https://user-images.githubusercontent.com/4335237/50617812-d6efab00-0ea3-11e9-863a-20573c75ba3c.png)
   

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