Re: pgbench - test whether a variable exists

> While investigating moving pgbench expressions to fe_utils so that they can 
> be shared with psql (\if ..., \let ?), I figure out that psql's \if has a 
> syntax to test whether a variable exists, which is not yet available to 
> pgbench.
>
> This patch adds the same syntax to pgbench expression so that they can 
> represent this expression, already accepted by psql's \if.
>
> Note that it is not really that useful for benchmarking, although it does not 
> harm.

Patch v2 is a rebase.

-- 
Fabien.