JSON[B] arrays are second-class citizens

From: David Fetter <david(at)fetter(dot)org>
To: PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: JSON[B] arrays are second-class citizens
Date: 2016-05-31 20:34:22
Message-ID: 20160531203422.GA14221@fetter.org
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Folks,

While querying some JSONB blobs at work in preparation for a massive
rework of the data infrastructure, I ran into things that really
puzzled me, to wit:

SELECT * FROM unnest('["a","b","c"]'::jsonb);
ERROR: function unnest(jsonb) does not exist

SELECT * FROM jsonb_array_elements('["a","b","c"]'::jsonb);
value
───────
"a"
"b"
"c"
(3 rows)

Similar things happen with the other functions matching

jsonb?_array_elements(_text)?

These functions correctly identify JSON[B] things which are not, at
their top level, arrays, and error out appropriately.

What this hints to me is that json_array_elements() and friends have
access to things that at least in theory UNNEST could have access to.

Is making those things accessible to UNNEST, etc., a reasonable
direction to go?

Another option I came up with is to make functions that match

jsonb?_array_elements(_text)?(_with_ordinality), but that seems
somewhat tedious and error-prone on the maintenance side.

What say?

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david(dot)fetter(at)gmail(dot)com

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