BigData / Tableau Interview Questions
What is a Tableau extract?
An extract is a compressed, optimized snapshot of your data that Tableau stores using its own Hyper engine format (.hyper files), instead of querying the original database live every time.
- Extracts can pull the full dataset or a filtered subset, and can even be aggregated to a higher grain to shrink file size.
- Because it's a local, columnar, purpose-built format, an extract is usually much faster to query than hitting the live source directly, especially over a slow database connection or large tables.
- Extracts need to be refreshed (manually or on a schedule via Tableau Server/Cloud) to stay up to date with the source system.
Data menu -> Extract -> Create Extract... -> choose rows/filters -> save as .hyper
Extracts are a common performance lever: workbooks that feel sluggish against a live connection often speed up dramatically once switched to an extract, at the cost of the data being only as fresh as the last refresh.
What engine and file format does a Tableau extract use?
What is the main trade-off of using an extract instead of a live connection?
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