Tom Lane-2 wrote > Stephen Frost < > sfrost@ > > writes: >> * Moshe Jacobson ( > moshe@ > ) wrote: >>> Any PG committers who can change this in 9.3? > >> It will certainly not be changed for 9.3. > > IMO, if we do anything about this at all, it should be to document the > "=" option not remove it. If we change it, the squawks from people who > were (perhaps unintentionally) depending on the current behavior will > outnumber the plaudits from people who think that such a change is a > good idea by several orders of magnitude. > > regards, tom lane *Nutshell* In short; I generally do not like undocumented behavior - especially for something that an inexperienced user is going to encounter without even thinking about it. "=" for assignment is so common that you need to decide to either allow it or not; many people will use it just to see if it works and then, if it does not, will RTFM and learn that they should instead be using ":=". GET DIAGNOSTICS is simply a special-form of the basic assignment and thus should have the same rules and documentation. The fact that we talking about documenting this as opposed to making it work reinforces this choice. Time will only make the problem worse. Either there is a strong enough argument NOW to do away with this dual-usage of "=" and we define the plan of action starting with warnings in 9.4 OR we document it for 9.3 (and, really, back to all supported versions). Crap or get off of the toilet. *Exposition* I have not gone and looked but I know there is some form of the "check function" routine floating around here and that routine could have a "strict assignment" option for those who want that safety check. That said, in the OP's example the code intended to use assignment and correctly did so. I am having trouble finding any example, let alone a compelling one, where allowing "=" to have both assignment and equality meanings would lead to silent bugs. This may be a lack of imagination on my part. The fact that assignment cannot occur in an expression while equality must is the reason for the difficulty. It is when assignment can occur in an expression (and thus, like equality, has a return value) that ambiguity (and thus bugs) arises. Pavel brings up the point of cross-language compatibility and learning and in general I would agree but, and again because of the exclusive syntax zones for assignment and equality in the "PL/PGSQL" language said compatibility can be something achieved at a higher level - plus I would think having more options would work in favor. If the issue is people moving their PostgreSQL code to Oracle then I am not sure whether I'd change the language to make that work more easily - I'd much rather keep everyone who has been using the "=" for assignment happy and let higher level compatibility tools handle the conversion. I agree with documenting the "GET DIAGNOSTICS var := item;" syntax and in fact from a purely OCD standpoint wonder why non-diagnostic assignment is documented for ":=" while diagnostic assignment is documented for "=". The "GET DIAGNOSTICS" part is a modifier for the statement but doesn't magically turn the construct into an expression. David J. P.S. Undocumented behavior should be considered "not yet documented" behavior. It isn't worth documenting everything but if an issue or confusion arises then at least document "we allow - for the following reasons - this behavior but recommend you do not rely on it - for the following reasons". The visibility of said documentation should be directly proportional to the level of experience of the user that will encounter said behavior. -- View this message in context: http://postgresql.1045698.n5.nabble.com/Strange-behavior-of-as-assignment-operator-tp5757205p5757631.html Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
