For simple AND-ed predicates, if the entire filter is eligible for pushdown then after pushdown the filter would be dropped, so the Explain plan will not show a Filter node. In this case, I would expect the row count of the Scan to be reduced. For complex predicates, e.g combination of ANDs and ORs or ones which involve expressions such as CAST etc., it is possible some part of the filter would be pushed into the Scan but the Filter node will remain. In this case, the row count of the Scan would not be reduced to avoid doing the reduction twice.
-Aman On Thu, Oct 26, 2017 at 5:33 AM, PROJJWAL SAHA <[email protected]> wrote: > Hello, > > One question, > How to verify whether predicate pushdown is happening ? > > I have one parquet file generated using CTAS command. I have executed > REFRESH METADATA. I am firing a simple query with a WHERE clause. In the > physical plan for the scan operation, i see rowcount as total number of > rows in the data. Should this value gets lowered in case of predicate > pushdown ? Is is necessary to sort the predicate column for this to take > effect ? Any pointers ? > > Regards, > Projjwal >
