2017-04-07 9:52 GMT+02:00 Fabien COELHO <coe...@cri.ensmp.fr>: > > Hello Corey, > > \if defined varname >>>> \if sql boolean expression to send to server >>>> \if compare value operator value >>>> >>> >>> I'm still thinking:-) >>> >>> Independently of the my aethetical complaint against having a pretty >>> unusual keyword prefix syntax, how would you envision a \set assignment >>> variant? Would \if have a different expression syntax somehow? >>> >> >> Any further thoughts? >> > > My current opinion: > > - I'm fine if \set stays as it is, i.e. no expression. > > - I agree that some client-side expressions are needed, along the > semantics suggested by Tom, i.e. definition and comparisons. > > - I'm really against the prefix syntax suggested by Tom > > > I wish I could have an explanation about why the :?varname (or some other > variant) syntax I suggested has a "namespace" issue. > > The advantage that I see is that although it is obviously ugly, it is ugly > in the continuity of the various :["'?]varname syntaxes already offered and > it allows to get rid of "defined varname" which does not look like SQL. A > second advantage is that with the "defined" proposal >
I don't think so this argument is valid - \if doesn't look like SQL too. > > \if defined var1 and defined var2 or defined var3 and sqlrt() >= .. > > Would probably never work work, as it cannot be embedded in another > expression, while it would work with > > \if :?var1 and :?var2 or :?var3 and ... > > I don't see any reason why first should not work and second should to work > > Moreover, I would like the condition syntax to be basically SQL & psql > variables, without explicit prefixes, with a transparent decision whether > it is evaluated client side or server side. > > As client-side expressions are pretty simple, ISTM that some regex could > be used for this purpose, eg for integer and boolean comparisons: > > ^\s*\d+\s*(=|<>|!=|<|<=|>|>=)\s*\d+\s*$ > ^\s*(bool...)\s*(=|<>|!=)\s*(bool...)\s*$ > ^\s*(NOT\s*)?(bool...)\s*$ > > So that one could just write the expressions without having to tell where > it is executed, eg > > \if :VERSION_NUM < 110000 > > Would lead to > > \if 100000 < 110000 > > Caught by the first regex, and evaluated with a few lines of code. I have a different opinion - the condition expression should not be SQL necessary. This language is oriented on client side operations. What is benefit from server side expression? Regards Pavel > > > -- > Fabien. > > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers >
