3 ms·
My criticisms are specifically about OLAP use cases. Real OLAP queries have joins and subqueries. I hear you about compatibility. I think this benchmark would
by georgewfraser 9y ago
My criticisms are specifically about OLAP use cases. Real OLAP queries have joins and subqueries.
I hear you about compatibility. I think this benchmark would be greatly improved by rewriting the query to include a subquery and a fact-to-fact join using the same table. For example, you could do a subquery where you find the longest and shortest ride for each driver each day, and then join that back to the full table and calculate something. That would do a much better job of exercising the key features of the query planner, while still being simple and compatible.
- buremba 9y agoReal OLAP queries usually don't have JOINs. Instead, the data is denormalized at ingestion nad WINDOW, CTE ans subqueries are used at query time.
- georgewfraser 9y agoThis was true 10 years ago. Many people building data warehouses today just use a normalized schema and write views with lots of joins. It’s a much simpler workflow and data warehouses have gotten so fast that this actually works.
- buremba 9y agoI don't know any technology that makes the JOINs efficient enough for low latency queries. If you're joining two tables that have billions of rows, you need too much memory and CPU resources in order to be able to map them. Do you know any DBMS that focuses on OLAP systems and suggest normalization?
- StreamBright 9y agoI can just second that. Most DWHs arr denormalized because columnar storage formats love repetition.