QVD Structure
- XML Header w/ Metadata
- Symbol table for efficient storage of field values
- Actual data in an optimized format
Benefits of QVDs
- SPEED
- Load 10-100 times faster than most other data formats / direct connections to databases
- Designed for Qlik
- Reduced Server Load
- Minimize load on source systems by loading into QVDs once
- Data Transformation Layer
- QVDs can enable a structured ETL process with a clear separation between each step
Optimized Load
These actions will break optimization and result in a standard load
- Concatenating fields together
- Applying functions to fields during the load, like as Date(), Upper(), or Num()
- Using WHERE clauses to filter the data
- Using MAPPING loads
Use trial and error to determine if an optimized load is broken when doing anything other than a standard LOAD * FROM QVD