Re: Re: [SQL] querying with index on jsonb slower than standard column. Why?

On 12/12/2014 04:44 PM, Tom Lane wrote:
> Josh Berkus <josh@agliodbs.com> writes:
>> Yeah, I believe the core problem is that Postgres currently doesn't have
>> any way to have variadic return times from a function which don't match
>> variadic input types.  Returning a value as an actual numeric from JSONB
>> would require returning a numeric from a function whose input type is
>> text or json.  So a known issue but one which would require a lot of
>> replumbing to fix.
> Well, it'd be easy to fix if we were willing to invent distinct operators
> depending on which type you wanted out (perhaps ->> for text output as
> today, add ->># for numeric output, etc).

That was my immediate reaction. Not sure about the operator name. I'd
tentatively suggest -># (taking an int or text argument) and #># taking
a text[] argument, both returning numeric, and erroring out if the value
is a string, boolean, object or array.


>    Doesn't seem terribly nice
> from a usability standpoint though.
>
> The usability issue could be fixed by teaching the planner to fold a
> construct like (jsonb ->> 'foo')::numeric into (jsonb ->># 'foo').
> But I'm not sure how we do that except in a really ugly and ad-hoc
> fashion.
>
>


I would be inclined to add the operator and see how cumbersome people
find it. I suspect in many cases it might be sufficient.

cheers

andrew