On Sat, Jan 11, 2014 at 10:06:27PM +0100, Pavel Stehule wrote: > > > > 2014/1/11 Tom Lane <tgl@sss.pgh.pa.us> > > Bruce Momjian <bruce@momjian.us> writes: > > Oh, I think you are right. I have reverted the patch. Attached is > > proposed documentation for '='. > > Meh. Variable initialization is only one of multiple cases (assignment, > GET DIAGNOSTICS; maybe others, I've not examined the grammar). Also, > if we do it like this, we're implying that both := and = are equally > preferred, which might not be the impression we want to leave. > > > GET DIAGNOSTICS is defined by standard - and there "=" should be allowed only - > although we allow ":=" too. It is a embedded SQL statement - although it is > implemented as plpgsql statement.
OK, docs updated for that. I assume OPEN and FOR also can take := or =, right?
> Same situation is with UPDATE statement - we don't allow ":=" there. > > > > I'd be a bit inclined to just stick a NOTE somewhere saying that "=" > can be used in place of ":=" for assignment. > > > ok > > If we accept it and we close this topic, then following comment should be > removed > > assign_operator : '=' /* not documented because it might be removed someday *
Comment updated. Patch attached.
Still I am missing message about preferred syntax (or we should to enhance GET DIAGNOSTICS doc about proprietary syntax).
PL/pgSQL, PL/SQL is mix of two languages: ADA and SQL - and their designers decided so embedded SQL statements will be placed in native SQL syntax (and ADA in simplified ADA syntax)
We have to find a agreement what we will prefer for PL/pgSQL:
The assign statement is "ADA" statement - ":=" is preferred
The GET DIAGNOSTICS is "SQL" statement - "=" is preferred
A newer SQL/PSM was designed differently - without this dichotomy - A assignment is emphased by syntax SET varname = value
A proper syntax is good information what is coming from - and It is good mental helper to understand a philosophy of stored procedures (that shares concepts with PL/SQL). Next argument is similarity with PL/SQL and SQL PL. This statement (GET DIAGNOSTICS) is supported on both environments and only "=" is allowed there.
