From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com> |
Cc: | Tim Dudgeon <tdudgeon(dot)ml(at)gmail(dot)com>, pgsql-sql(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Re: [SQL] querying with index on jsonb slower than standard column. Why? |
Date: | 2014-12-12 23:27:31 |
Message-ID: | 548B79E3.5070301@dunslane.net |
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Lists: | pgsql-performance pgsql-sql |
On 12/12/2014 04:44 PM, Tom Lane wrote:
> Josh Berkus <josh(at)agliodbs(dot)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
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