Re: Jumble Query with COERCE_SQL_SYNTAX

Hi,

On Tue, Mar 29, 2022 at 03:52:57PM +0300, Yura Sokolov wrote:
> 
> v14 introduced the way to get original text for some kind of expressions
> using new 'funcformat' - COERCE_SQL_SYNTAX:
> - EXTRACT(part from timestamp)
> - (text IS [form] NORMALIZED)
> and others.
> 
> Mentioned EXTRACT and NORMALIZED statements has parts, that are not
> usual arguments but some kind of syntax. At least, there is no way to:
> 
>     PREPARE a(text) as select extract($1 from now());
> 
> But JumbleExpr doesn't distinguish it and marks this argument as a
> variable constant, ie remembers it in 'clocations'.
> 
> I believe such "non-variable constant" should not be jumbled as
> replaceable thing.

Yeah, the problem is really that those are some form of sublanguage inside SQL,
which is always a mess :(

It's probably an implementation detail that we treat those as syntactic sugar
for plain function calls, but since that's what we're doing I don't think it's
really sensible to change that.  For instance, for the query jumbler using this
query or "select pg_catalog.extract($1, now())" are identical, and that form
can be prepared.  Maybe it would make sense to allow a parameter for the
EXTRACT(x FROM y), since we're already allowing a non-standard form with
plain string literal?  The story is a bit different for NORMALIZED though.