Queries can be as complex as necessary, they just have to fit in one line.
Line continuation in general is missed though I thought something already when in for 10.0 that improves upon this...
In no way at all,in the sense that, either you choose to use an SQL evaluator, or a client-side evaluator (if it exists), or a backtick expression. They are mutually exclusive for a single \if invocation.
Client-side evaluation would have to be called with a syntax that is unambiguously different.
Is that the universe: server, client, shell?
Shell already has backticks required
Server, being the most common, ideally wouldn't need demarcation
Client thus would want its own symbol pairing to distinguish it from server.
Server doesn't need a leading marker but do we want to limit it to single statements only and allow an optional trailing semi-colon (or backslash command) which, if present, would end the "server" portion of the string and allow for treatment of additional terms on the same line to be parsed in a different context?
I'm conceptually for the implied "SELECT" idea. It overlaps with plpgsql syntax.
