starocean999 opened a new issue, #8894: URL: https://github.com/apache/incubator-doris/issues/8894
### Search before asking - [X] I had searched in the [issues](https://github.com/apache/incubator-doris/issues?q=is%3Aissue) and found no similar issues. ### Description TPCH q17: select sum(l_extendedprice) / 7.0 as avg_yearly from lineitem, part where p_partkey = l_partkey and p_brand = 'Brand#23' and p_container = 'MED BOX' and l_quantity < ( select 0.2 * avg(l_quantity) from lineitem where l_partkey = p_partkey ); If we rewrite the query as follows, the scan rows of lineitem in subquery will much less than old q17 as well as the less row count for group node. TPCH Q17(rewrite): select sum(l_extendedprice) / 7.0 as avg_yearly from lineitem, part p1 where p_partkey = l_partkey and p_brand = 'Brand#23' and p_container = 'MED BOX' and l_quantity < ( select 0.2 * avg(l_quantity) from lineitem, part p2 where l_partkey = p1.p_partkey and l_partkey = p2.p_partkey and p2.p_brand = 'Brand#23' and p2.p_container = 'MED BOX' ); Although we might push some predicate to subquery to minimize the original scan row count, it will also introduce a new table and a new join node, which results more rows to scan, filter and join. In TPCH Q2 and Q17, the pushed table is relatively small, so get better performance after pushing. But normally, a CBO optimizer is needed to decide if the pushing is worth. At last, if table spool optimizer is implemented, we can always push the predicates. ### Solution 1. Push the predicate to subquery in some case. 2. Add a session variable to control if enable this behavior. ### Are you willing to submit PR? - [X] Yes I am willing to submit a PR! ### Code of Conduct - [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct) -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
