On Fri, 2023-07-07 at 07:36 +0000, PG Doc comments form wrote: > i have a discussion in pgsql-bugs@lists.postgresql.org about this and it is > mentioned in the answers that it is documented and a "feature" of Postgres > that this can be done. > If this is wanted the documentation > (https://www.postgresql.org/docs/current/sql-select.html) that mentioned: > [execution order of SELECT that says that GROUP BY is before SELECT] > isn't correct because how can 4.) be done and the alias from 5.) is used? > Here is a hint important that there is an exception for alias used in group > by
I think that is already documented:
I think the complaint is that someone seeing the behavior in the wild comes to this order-of-operations and doesn't see that the observed behavior is documented. Sure, they can go into the GROUP BY section and figure out that there is a "oh, by the way" comment within there that output columns/aliases are indeed allowed. But I tend to agree that a mention in the "order of operations" section that output columns from step 5 can be seen in step 4 seems like an improvement if we really want the order of operations to be the main reference entry point for people trying to work out query behavior. Something like: "(while unadvised it is possible for the aliases defined in the next step to be used here as well)".