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In-Reply-To: <d6f116eb11dd8b5084cd218cfb34ce57@anastigmatix.net>
From: Andy Fan <zhihui.fan1213@gmail.com>
Date: Mon, 21 Aug 2023 18:58:05 +0800
Message-ID: <CAKU4AWphRdQUmdw0cnR8PixYsfoxmncQi9+=8gaEy23MTNmR5w@mail.gmail.com>
Subject: Re: Extract numeric filed in JSONB more effectively
To: Chapman Flack <chap@anastigmatix.net>
Cc: jian he <jian.universality@gmail.com>, Pavel Stehule <pavel.stehule@gmail.com>, 
	Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers <pgsql-hackers@postgresql.org>
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>
>
> Interestingly, when I relabel both places, like this:
>
>      Oid   targetOid = fexpr->funcresulttype;
>      Const *target  = makeConst(
>        OIDOID, -1, InvalidOid, sizeof(Oid),
>        ObjectIdGetDatum(targetOid), false, true);
>      RelabelType *rTarget = makeRelabelType((Expr *)target,
>        INTERNALOID, -1, InvalidOid, COERCE_IMPLICIT_CAST);
>      fexpr->funcid = new_func_id;
>      fexpr->args = opexpr->args;
>      fexpr->args = list_insert_nth(fexpr->args, 0, rTarget);
>      expr = (Expr *)makeRelabelType((Expr *)fexpr,
>        targetOid, -1, InvalidOid, COERCE_IMPLICIT_CAST);
>    }
>    PG_RETURN_POINTER(expr);
>
> EXPLAIN looks like this:
>
>   Seq Scan on pg_temp.test_jsonb
>     Output: jsonb_array_element_type(('23'::oid)::internal, test_json,
> 0), (test_json -> 0)
>     Filter: (test_jsonb.json_type = 'scalarint'::text)
>
> With COERCE_IMPLICIT_CAST both places, the relabeling of the
> function result is invisible, but the relabeling of the argument
> is visible.
>
>
I think this is because get_rule_expr's showimplicit is always
true for args in this case, checking the implementation of
get_rule_expr, I found PG behavior like this in many places.

-- 
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>
Interestingly, when I relabel both places, like this:<br>
<br>
=C2=A0 =C2=A0 =C2=A0Oid=C2=A0 =C2=A0targetOid =3D fexpr-&gt;funcresulttype;=
<br>
=C2=A0 =C2=A0 =C2=A0Const *target=C2=A0 =3D makeConst(<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0OIDOID, -1, InvalidOid, sizeof(Oid),<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0ObjectIdGetDatum(targetOid), false, true);<br>
=C2=A0 =C2=A0 =C2=A0RelabelType *rTarget =3D makeRelabelType((Expr *)target=
,<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0INTERNALOID, -1, InvalidOid, COERCE_IMPLICIT_CAS=
T);<br>
=C2=A0 =C2=A0 =C2=A0fexpr-&gt;funcid =3D new_func_id;<br>
=C2=A0 =C2=A0 =C2=A0fexpr-&gt;args =3D opexpr-&gt;args;<br>
=C2=A0 =C2=A0 =C2=A0fexpr-&gt;args =3D list_insert_nth(fexpr-&gt;args, 0, r=
Target);<br>
=C2=A0 =C2=A0 =C2=A0expr =3D (Expr *)makeRelabelType((Expr *)fexpr,<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0targetOid, -1, InvalidOid, COERCE_IMPLICIT_CAST)=
;<br>
=C2=A0 =C2=A0}<br>
=C2=A0 =C2=A0PG_RETURN_POINTER(expr);<br>
<br>
EXPLAIN looks like this:<br>
<br>
=C2=A0 Seq Scan on pg_temp.test_jsonb<br>
=C2=A0 =C2=A0 Output: jsonb_array_element_type((&#39;23&#39;::oid)::interna=
l, test_json, <br>
0), (test_json -&gt; 0)<br>
=C2=A0 =C2=A0 Filter: (test_jsonb.json_type =3D &#39;scalarint&#39;::text)<=
br>
<br>
With COERCE_IMPLICIT_CAST both places, the relabeling of the<br>
function result is invisible, but the relabeling of the argument<br>
is visible.<br>
<br></blockquote><div><br></div><div>I think this is because=C2=A0get_rule_=
expr&#39;s showimplicit is always</div><div>true for args in this case, che=
cking the implementation of=C2=A0</div><div>get_rule_expr, I found PG behav=
ior like this in many places.<br></div>


</div><div><br></div><span 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></div></div>

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