Cloud Data Warehouse Questions
RajneeshShukla
Solution Architect at a tech vendor with 10,001+ employees

I have seen bitmap index as the preferred choice in a data warehousing environment. I wanted to know reasons for that. As per my own experience, one reason is bitmap indexes are compressed and hence confined in less index space. When we have large number of FK indexes then this index space matters. Bitmap indexes will enable faster search and hence reduced response time in such cases. 


I wanted to hear other reasons for this from experts.


As per my own research, bitmap works well for low cardinality columns, however DWH may not necessarily have low cardinality columns.

Gouri MishraBitmap indexes are useful for low cardinality column(s) for 3 primary reasons… more »
RajneeshShukla
Solution Architect at a tech vendor with 10,001+ employees

I am a solution architect for a global tech vendor.


I am looking for any general guidelines to allocate tablespace quota to different layers/schemas in the ETL flow of a data warehouse (% of total space in each layer).


I have these 4 layers:



  1. Staging -truncate and load data from source files

  2. ODS- Type 1 persistent tables

  3. Transformation layer- similar to final DWH layer but truncate before loading newly arrived data

  4. DWH layer- Final dimensional model layer


I understand space requirements may vary based on project requirements, however, any general guideline (if any such in data warehousing and ETL space) to estimate the space will be helpful.

Thanks! I appreciate your help.

Gouri MishraSpace requirement will be directly dependent on design considerations and data… more »
RajneeshShukla
Solution Architect at a tech vendor with 10,001+ employees

I am a solution architect for a global tech company with over ten years of experience.

What are the benefits of having separate layers or a dedicated schema for each layer in ETL? One dedicated layer for staging, one for type 1 persistent tables, and a dedicated schema/layer for tables at a dimensional model? Why it is not recommended to have all tables in one schema?

Thanks! I appreciate your help. 

Gouri MishraHere are some of the advantages of managing data in different layers: 1.… more »