po 31. 12. 2018 v 3:15 odesÃlatel Chapman Flack <c...@anastigmatix.net> napsal:
> On 12/30/18 15:18, Pavel Stehule wrote: > > ne 30. 12. 2018 v 20:06 odesÃlatel Chapman Flack <c...@anastigmatix.net> > > napsal: > >> How difficult would it be to make the grammar constructs that currently > >> accept "BY REF" (only as noise and ignore it) accept and ignore both BY > REF > >> and BY VALUE? > > > > This is difficult question - a implementation is probably very easy, but > it > > is hard to accept to possible break compatibility due syntactic sugar. > > > > This is not probably related to just XPath/XQuery question - but it is > > related to different design of XML datatype (based on PostgreSQL TOAST) > > against ANSI/SQL (Oracle - clob). > > > > So this is complicated topic and my opinion is better to don't touch it > > because we can't to fix it, change it - and I am not sure so ANSI/SQL is > > significantly better than PostgreSQL implementation. > > I am not sure I understand your point. It appears that Oracle (18c), > just like PostgreSQL, really only supports BY VALUE semantics. Here is > an Oracle fiddle that shows it: > > > https://dbfiddle.uk/?rdbms=oracle_18&fiddle=0cb353da0d94c6d5c2659222a1e419fd > > When the same element is passed via two parameters, an 'is' test (node > identity equality) of the two parameters returns false, indicating that > Oracle has used BY VALUE semantics, not BY REF. > > Oracle uses BY VALUE when BY VALUE is explicitly requested, and also when > no passing method is specified (i.e., BY VALUE is the default). Oracle also > uses BY VALUE when BY REF is explicitly requested, which seems rather rude, > but that must be the behavior PostgreSQL is imitating with the choice to > accept and ignore BY REF. > > But the PostgreSQL situation is a little more strange. PG uses BY VALUE > semantics as the default when no passing method is specified. PG also uses > BY VALUE semantics when BY REF is explicitly requested, which is rude, > just like Oracle. But why should an explicit specification of BY VALUE > (which is, after all, the semantics we're going to use anyway!) produce > this? > > ERROR: syntax error at or near "value" > > To me, that doesn't seem like least astonishment. > > I am not seeing what would be complicated about removing that astonishment > by simply allowing the grammar productions to also consume BY VALUE and > ignore it. > ok - I am not against implementation of ignored BY VALUE. But I don't like a idea to disable BY REF. Regards Pavel > > -Chap >
