Re: [HACKERS] \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)

    Tom Lane wrote:

> OT_WHOLE_LINE is not what you want because that results in verbatim
> copying, without variable expansion or anything

But if we want to implement "\if defined :foo" in the future
isn't it just what we need?

Also we could leave open the option to accept an SQL expression
here. I expect people will need SQL as the evaluator in a lot of cases.
So far we need to do that:
 SELECT sql_expr ... AS varname \gset \if :varname ... \endif

Surely users will wonder right away why they can't write it like this
instead:
 \if (sql_expr) ... \endif

There's a precedent with \copy accepting a query inside parentheses,
using OT_WHOLE_LINE.


Best regards,
--
Daniel Vérité
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