Dandandan edited a comment on issue #1082: URL: https://github.com/apache/arrow-datafusion/issues/1082#issuecomment-942674160
> psql doesn't seem to have direct `SEMI JOIN`. It uses `IN` to do the same thing as `SEMI JOIN`. So how to use `is distinct from` in `select distinct a from foo where a in (select a from bar);`? We also don't have the semi / anti join SQL syntax, but we support semi and anti join in a `LogicalPlan` and support it in the hash join nodes / implementation. We don't need it at the syntax level to support operators like `INTERSECT`, as long as we can map the input query to a logical plan / physical plan. I didn't have a look at using select distinct + semi join for `INTERSECT` but if it's equivalent that totally makes sense to me. Complication with using things like `is distinct from` will not supported by a equi-join implementation (which only supports `A=B` type of expressions), so I'm not sure if this is an efficient / easy way to implement it. I think supporting the `is distinct from` operator is useful in itself. -- 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: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
