On Fri, Mar 7, 2014 at 11:51 PM, Dominique Devienne <ddevie...@gmail.com> wrote:
>
> basically register_function('rpad', 'x', 'y', 'printf(''%-*s'', y,
> x)') would register a 2-arg function (register_function's argc-2)
> named $argv[0], which executes the following statement
>
> with args($argv[1], $argv[2], ... $argv[argc-2]) as (VALUES(?, ?))
> select $argv[argc-1) from args;
>
Dominique, your variant is even better than using numbered parameters.
If you use named ones supported by sqlite (:VVV) then sqlite will do
the job of the textual replacement with bind api itself (
'printf(''%-*s'', :y,> :x)' )
The small problem in this case is that there are two ways (times) to
check whether named parameter exists in the expression. Either when
the registered function executed (and report error about lacking some
parameters only here) or make a test call with some test parameters at
the time of registration.
The latter allows revealing errors earlier, but it has no knowledge
about the expression so might fire strange run-time errors (division
by zero etc). If we omit execution and leave only binding, we might
miss the case when not all binding variables mentioned in the
expression, actually provided (example ... 'somefunc', 'x', 'y', ':x +
:y + :z')
Max
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