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Re: JSON in 9.2 - Could we have just one to_json() function instead of two separate versions ?

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: Joey Adams <joeyadams3(dot)14159(at)gmail(dot)com>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, PavelStehule <pavel(dot)stehule(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: JSON in 9.2 - Could we have just one to_json() function instead of two separate versions ?
Date: 2012-05-01 16:22:25
Message-ID: CAD5tBc+qHrNKth+qT-hQmT5RTTaABfjabd-r4acLy9HdwBm7hg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, May 1, 2012 at 9:05 AM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:

> On Tue, May 1, 2012 at 10:49 AM, Joey Adams <joeyadams3(dot)14159(at)gmail(dot)com>
> wrote:
> > On Tue, May 1, 2012 at 8:02 AM, Hannu Krosing <hannu(at)2ndquadrant(dot)com>
> wrote:
> >> Hi hackers
> >>
> >> After playing around with array_to_json() and row_to_json() functions a
> >> bit it I have a question - why do we even have 2 variants *_to_json()
> >
> > Here's the discussion where that decision was made:
> >
> > http://archives.postgresql.org/pgsql-hackers/2012-01/msg01339.php
> >
> > To quote:
> >
> >>>> why not call all these functions 'to_json' and overload them?
> >>>
> >>> I don't honestly feel that advances clarity much. And we might want to
> overload each at some stage with options that are specific to the datum
> type. We have various foo_to_xml() functions now.
> >>
> >> -1
> >>
> >> older proposal is more consistent with xml functions
> >
> > The most compelling argument I see here is the one about options
> > specific to the datum type.
>
> I don't find that to be particularly compelling at all.  to_timestamp
> for example supports multiple argument versions depending on the input
> type.
>
> >  * If the JSON type does not yet support, say, converting from a
> > number, it will be apparent from the names and types of the functions,
> > rather than being a hidden surprise.  On the other hand, array_to_json
> > and composite_to_json already convert ANY values to JSON, so this
> > doesn't matter, anyway.
>


I am away from base on a consulting assignment all this week, so my
connectivity and time are severely limited, and I don't have time to
respond in depth.

Let me just point out two things. First, we are approaching a beta release.
The time for changing this is long since gone, IMNSHO.

Second, RFC 4627 is absolutely clear: a valid JSON value can only be an
object or an array, so this thing about converting arbitrary datum values
to JSON is a fantasy. If anything, we should adjust the JSON input routines
to disallow anything else, rather than start to output what is not valid
JSON.


cheers

andrew

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