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help / color / mirror / Atom feedFrom: Andrew Dunstan <andrew@dunslane.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: Tim Dudgeon <tdudgeon.ml@gmail.com>
Cc: pgsql-sql@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: Re: [SQL] querying with index on jsonb slower than standard column. Why?
Date: Fri, 12 Dec 2014 22:05:20 -0500
Message-ID: <548BACF0.5040909@dunslane.net> (raw)
In-Reply-To: <15863.1418433637@sss.pgh.pa.us>
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On 12/12/2014 08:20 PM, Tom Lane wrote:
> We can't just add the operator and worry about usability later;
> if we're thinking we might want to introduce such an automatic
> transformation, we have to be sure the new operator is defined in a
> way that allows the transformation to not change any semantics.
> What that means in this case is that if (jsonb ->> 'foo')::numeric
> would have succeeded, (jsonb ->># 'foo') has to succeed; which means
> it'd better be willing to attempt conversion of string values to
> numeric, not just throw an error on sight.
>
>
Well, I'm not 100% convinced about the magic transformation being a good
thing.
Json numbers are distinct from strings, and part of the justification
for this is to extract a numeric datum from jsonb exactly as stored, on
performance grounds. So turning round now and making that turn a string
into a number if possible seems to me to be going in the wrong direction.
cheers
andrew
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Cc: andrew@dunslane.net, tgl@sss.pgh.pa.us, josh@agliodbs.com, tdudgeon.ml@gmail.com, pgsql-performance@postgresql.org
Subject: Re: Re: [SQL] querying with index on jsonb slower than standard column. Why?
In-Reply-To: <548BACF0.5040909@dunslane.net>
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