From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, 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: | 2014-12-13 03:05:20 |
Message-ID: | 548BACF0.5040909@dunslane.net |
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Lists: | pgsql-performance pgsql-sql |
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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