mingmwang opened a new issue, #5492: URL: https://github.com/apache/arrow-datafusion/issues/5492
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.** <!-- A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] (This section helps Arrow developers understand the context and *why* for this feature, in addition to the *what*) --> In the current DataFusion, it has very limited support for correlated subqueries. It can only decorrelate the (NOT) IN/Exists predicate subqueries to Semi/Anti Joins. Even in the simplest IN/Exists cases, if the correlated expressions are not in the Filter/Join conditions, the current decorrelate rules will not support them. In the paper "Unnesting Arbitrary Queries" by T. Neumann; A. Kemper (http://www.btw-2015.de/res/proceedings/Hauptband/Wiss/Neumann-Unnesting_Arbitrary_Querie.pdf). It raise a mechanism to unnest arbitrary queries. This was already implemented by the Hyper DB: For example: select * from orders where 1 in (select 1 from part left join (select l_partkey from lineitem where o_orderkey = 2) lineitem on p_partkey = lineitem.l_partkey) https://hyper-db.de/interface.html# Both SparkSQL and PostgreSQL do not support decorrelate such kind of queries. **Describe the solution you'd like** <!-- A clear and concise description of what you want to happen. --> **Describe alternatives you've considered** <!-- A clear and concise description of any alternative solutions or features you've considered. --> **Additional context** <!-- Add any other context or screenshots about the feature request here. --> -- 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]
