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

Hello Tom,

>> pgbench (well, at least if I succeed in getting boolean expressions and
>> setting variables, which is just a maybe), but this kind of if in the
>> middle of expression does not make much sense for a pgbench script where
>> "if" must be evaluated at execution time, not parse time.
>
> Well, it's not really clear to me why that would be true.

For example, how can you PREPARE a possibly combinatorial thing?

SELECT
\if ... XX \else YY \endif
FROM
\if ... ZZ \else WW \endif
WHERE
\if ... AA \else BB \endif
;

Or the kind of operation:

\if ...
SELECT *
\else
DELETE
\endif
FROM table WHERE condition;

Even the structure can be changed somehow:

SELECT
\if ...
1 ;
SELECT 2
\endif
;

> If it actually is impossible to give pgbench equivalent behavior, we'll
> just have to live with the discrepancy,

Yep.

> but ISTM it could probably be made to work.

Even if it could somehow, I do not see it as a useful feature for pgbench.
I also lack a good use case for psql for this feature.

--
Fabien.