"David G. Johnston" <david.g.johns...@gmail.com> writes: > On Thursday, July 13, 2017, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Maybe we can hack ruleutils to use >> the CAST syntax only in this specific context.
> Given the lack of complaints, and ubiquity of ::, this would seem ideal > and sufficient. While there is something to be said for using standard > compliant syntax changing just this like doesn't seem like it would move > the goalposts meaningfully. Hm, it's worse than I thought: the argument of the CAST expression needn't be a function call at all, and on top of that, the parser will throw away a no-op cast altogether. So for example: regression=# create view vvc as select * from cast(1+2 as int) c(x); CREATE VIEW regression=# \d+ vvc View "public.vvc" Column | Type | Collation | Nullable | Default | Storage | Description --------+---------+-----------+----------+---------+---------+------------- x | integer | | | | plain | View definition: SELECT c.x FROM 1 + 2 c(x); To make the world safe for this behavior by extending the grammar, we'd have to be prepared to accept an arbitrary a_expr, without even surrounding parentheses, as a FROM item. I don't think there's much chance of making that work without grammar conflicts, and even if we managed, the SQL committee would probably find a way to break it with some future feature addition. So what I'm now thinking is to make ruleutils.c look at the expression in an RTE_FUNCTION FROM item and see if it will decompile as something with the syntax of a function call. If not, or if there's any doubt, emit a dummy CAST(... AS sametype) around it. That would cause the above example to come out the way it went in. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers