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From: Andy Fan <zhihui.fan1213@gmail.com>
Date: Mon, 14 Aug 2023 15:06:30 +0800
Message-ID: <CAKU4AWp+KLes8g=BWLqZfDmW9+=ZY0UC4G0i3qVcYEviK_dDTA@mail.gmail.com>
Subject: Re: Extract numeric filed in JSONB more effectively
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, jian he <jian.universality@gmail.com>, 
	pgsql-hackers <pgsql-hackers@postgresql.org>
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>
>
> We'd still have functions like jsonb_field_as_numeric() under the
> hood, but there's not an expectation that users call them explicitly.
>

To avoid the lots of functions like jsonb_field_as_int2/int4, I defined
Datum jsonb_object_field_type(.., Oid target_oid) at last,  so the
function must return "internal" or "anyelement".  Then we can see:

select jsonb_object_field_type(tb.a, 'a'::text, 1700) from tb;
ERROR:  cannot display a value of type anyelement.

The reason is clear to me, but  I'm not sure how to fix that or deserves
a fix? Or shall I define jsonb_object_field_int2/int8 to avoid this?

This is an unresolved issue at the latest patch.
-- 
Best Regards
Andy Fan

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<div dir=3D"ltr"><div class=3D"gmail_quote"><blockquote class=3D"gmail_quot=
e" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204)=
;padding-left:1ex"><br>
We&#39;d still have functions like jsonb_field_as_numeric() under the<br>
hood, but there&#39;s not an expectation that users call them explicitly.<b=
r></blockquote><div><br></div><div>To avoid the lots of functions like json=
b_field_as_int2/int4, I defined</div><div>Datum jsonb_object_field_type(..,=
 Oid target_oid) at last,=C2=A0 so the</div><div>function must return &quot=
;internal&quot; or &quot;anyelement&quot;.=C2=A0 Then we can see:</div><div=
><br></div>select jsonb_object_field_type(tb.a, &#39;a&#39;::text, 1700) fr=
om tb;<br>ERROR: =C2=A0cannot display a value of type anyelement.</div><div=
 class=3D"gmail_quote"><br></div><div class=3D"gmail_quote">The reason is c=
lear to me, but=C2=A0 I&#39;m not sure how to fix=C2=A0that or deserves</di=
v><div class=3D"gmail_quote">a fix? Or shall I define jsonb_object_field_in=
t2/int8 to avoid this?=C2=A0</div><div class=3D"gmail_quote"><div><br></div=
><div>This is an unresolved issue at the latest patch.=C2=A0</div></div><sp=
an class=3D"gmail_signature_prefix">-- </span><br><div dir=3D"ltr" class=3D=
"gmail_signature"><div dir=3D"ltr">Best Regards<div>Andy Fan</div></div></d=
iv></div>

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