On 12/12/2014 04:44 PM, Tom Lane wrote:
Josh Berkus <josh@xxxxxxxxxxxx> 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
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