[WIP] Refactor Index Generatorcode

[kumarvishal09]

Be sure to do all of the following checklist to help us incorporate
your contribution quickly and easily:

• Any interfaces changed?

• Any backward compatibility impacted?

• Document update required?

• Testing done
  Please provide details on
  - Whether new unit test cases have been added or why no new tests are required?
  - How it is tested? Please attach test report.
  - Is it a performance related change? Please attach the performance test report.
  - Any additional information to help reviewers in testing this change.

• For large changes, please consider breaking it into sub-tasks under an umbrella JIRA.

[CarbonDataQA]

Build Failed with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/319/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8390/

[CarbonDataQA]

Build Failed with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/151/

[CarbonDataQA]

Build Success with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/154/

[CarbonDataQA]

Build Failed with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/322/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8393/

[CarbonDataQA]

Build Success with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/157/

[CarbonDataQA]

Build Failed with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/325/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8396/

[CarbonDataQA]

Build Success with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/158/

[CarbonDataQA]

Build Failed with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/326/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8397/

[CarbonDataQA]

Build Failed with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/335/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8406/

[CarbonDataQA]

Build Failed with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/167/

[CarbonDataQA]

Build Success with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/169/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8408/

[CarbonDataQA]

Build Success with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/337/

[brijoobopanna]

retest this please

[CarbonDataQA]

Build Success with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/204/

[CarbonDataQA]

Build Success with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/373/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.3/8443/

[CarbonDataQA]

Build Failed with Spark 2.3.1, Please check CI http://136.243.101.176:8080/job/carbondataprbuilder2.3/8532/

[CarbonDataQA]

Build Success with Spark 2.1.0, Please check CI http://136.243.101.176:8080/job/ApacheCarbonPRBuilder2.1/287/

[CarbonDataQA]

Build Failed with Spark 2.2.1, Please check CI http://95.216.28.178:8080/job/ApacheCarbonPRBuilder1/462/