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
\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 ...
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.
--
Fabien.
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