I was looking for something in the New Features Manual and I had a total WTF moment when I saw this stuff.
If you look at the final section of the article, you can see in some cases these just get transformed to regular joins and outer joins, but there is certainly something else under the hood, as shown by the pipelined table function example.
I think it’s going to take me a long time before I think of using these in my regular SQL…
Update: The optimizer has used
LATERAL inline views during some query transformations for some time, but they were not documented and therefore not supported for us to use directly until now. Thanks to Dominic Brooks and Sayan Malakshinov for the clarification.