On 09/26/2012 01:46 PM, Tom Lane wrote:
Andrew Dunstan <and...@dunslane.net> writes:
Drawing together various discussions both here and elsewhere (e.g. the
PostgresOpen hallway track) I propose to work on the following:
1. make datum_to_json() honor a type's cast to json if it exists. The
fallback is to use the type's string representation, as now.
2. add a cast hstore -> json (any others needed for core / contrib types ?)
3. add a to_json(anyelement) function
4. add a new aggregate function json_agg(anyrecord) -> json to simplify
and make more effecient turning a resultset into json.
Comments welcome.
ISTM the notion of to_json(anyelement) was already heavily discussed and
had spec-compliance issues ... in fact, weren't you one of the people
complaining? What exactly does #3 mean that is different from the
previous thread?
I thought I got shouted down on that issue. The main reason we didn't
include it was that it was getting rather late for those changes, IIRC -
we only just got in any json stuff at all in under the wire.
And in fact you can have a json value now that's not an array or object:
andrew=# select json '1' as num, json '"foo"' as txt;
num | txt
-----+-------
1 | "foo"
Also, on reflection I'm not sure about commandeering cast-to-json for
this --- aren't we really casting to "json member" or something like
that? The distinction between a container and its contents seems
important here. With a container type as source, it might be important
to do something different if we're coercing it to a complete JSON
value versus something that will be just one member. I'm handwaving
here because I don't feel like going back to re-read the RFC, but
it seems like something that should be considered carefully before
we lock down an assumption that there can never be a difference.
I think in view of the above this would be moot, no?
cheers
andrew
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