alamb commented on issue #128: URL: https://github.com/apache/arrow-datafusion/issues/128#issuecomment-826832822
Comment from Daniël Heres(Dandandan) @ 2020-12-22T13:07:20.151+0000: <pre>Found some nice material from Spark on this: [https://databricks.com/blog/2017/08/31/cost-based-optimizer-in-apache-spark-2-2.html] basically the idea to use column level statistics such as: * min/max * nr of distinct values * null count to come up with e.g. selectivity of a filter. Also there is a formula for (inner) join cardinality: {{num(A IJ B) = num(A)*num(B)/max(distinct(A.k),distinct(B.k))}}</pre> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
