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From: Florents Tselai <florents.tselai@gmail.com>
Date: Wed, 5 Mar 2025 21:29:50 +0200
Message-ID: <CA+v5N42PVJH3HbwLE1yC75XR6E5zGnCCdtSUXfgFwtGyPP8XYg@mail.gmail.com>
Subject: Re: PATCH: jsonpath string methods: lower, upper, initcap, l/r/btrim,
 replace, split_part
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers <pgsql-hackers@lists.postgresql.org>, 
	Andrew Dunstan <andrew@dunslane.net>, Peter Eisentraut <peter@eisentraut.org>
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On Thu, Sep 26, 2024 at 1:55=E2=80=AFPM Alexander Korotkov <aekorotkov@gmai=
l.com>
wrote:

> On Thu, Sep 26, 2024 at 12:04=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wro=
te:
> > Florents Tselai <florents.tselai@gmail.com> writes:
> > > This patch is a follow-up and generalization to [0].
> > > It adds the following jsonpath methods:  lower, upper, initcap,
> l/r/btrim,
> > > replace, split_part.
> >
> > How are you going to deal with the fact that this makes jsonpath
> > operations not guaranteed immutable?  (See commit cb599b9dd
> > for some context.)  Those are all going to have behavior that's
> > dependent on the underlying locale.
> >
> > We have the kluge of having separate "_tz" functions to support
> > non-immutable datetime operations, but that way doesn't seem like
> > it's going to scale well to multiple sources of mutability.
>
> While inventing "_tz" functions I was thinking about jsonpath methods
> and operators defined in standard then.  Now I see huge interest on
> extending that.  I wonder if we can introduce a notion of flexible
> mutability?  Imagine that jsonb_path_query() function (and others) has
> another function which analyzes arguments and reports mutability.  If
> jsonpath argument is constant and all methods inside are safe then
> jsonb_path_query() is immutable otherwise it is stable.  I was
> thinking about that back working on jsonpath, but that time problem
> seemed too limited for this kind of solution.  Now, it's possibly time
> to shake off the dust from this idea.  What do you think?
>

I was thinking about taking another stab at this.
Would someone more versed in the inner workings of jsonpath like to weigh
in on the immutability wrt locale?

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<div dir=3D"ltr"><div dir=3D"ltr"><div><br></div></div><br><div class=3D"gm=
ail_quote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On T=
hu, Sep 26, 2024 at 1:55=E2=80=AFPM Alexander Korotkov &lt;<a href=3D"mailt=
o:aekorotkov@gmail.com">aekorotkov@gmail.com</a>&gt; wrote:<br></div><block=
quote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left-w=
idth:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding=
-left:1ex">On Thu, Sep 26, 2024 at 12:04=E2=80=AFAM Tom Lane &lt;<a href=3D=
"mailto:tgl@sss.pgh.pa.us" target=3D"_blank">tgl@sss.pgh.pa.us</a>&gt; wrot=
e:<br>
&gt; Florents Tselai &lt;<a href=3D"mailto:florents.tselai@gmail.com" targe=
t=3D"_blank">florents.tselai@gmail.com</a>&gt; writes:<br>
&gt; &gt; This patch is a follow-up and generalization to [0].<br>
&gt; &gt; It adds the following jsonpath methods:=C2=A0 lower, upper, initc=
ap, l/r/btrim,<br>
&gt; &gt; replace, split_part.<br>
&gt;<br>
&gt; How are you going to deal with the fact that this makes jsonpath<br>
&gt; operations not guaranteed immutable?=C2=A0 (See commit cb599b9dd<br>
&gt; for some context.)=C2=A0 Those are all going to have behavior that&#39=
;s<br>
&gt; dependent on the underlying locale.<br>
&gt;<br>
&gt; We have the kluge of having separate &quot;_tz&quot; functions to supp=
ort<br>
&gt; non-immutable datetime operations, but that way doesn&#39;t seem like<=
br>
&gt; it&#39;s going to scale well to multiple sources of mutability.<br>
<br>
While inventing &quot;_tz&quot; functions I was thinking about jsonpath met=
hods<br>
and operators defined in standard then.=C2=A0 Now I see huge interest on<br=
>
extending that.=C2=A0 I wonder if we can introduce a notion of flexible<br>
mutability?=C2=A0 Imagine that jsonb_path_query() function (and others) has=
<br>
another function which analyzes arguments and reports mutability.=C2=A0 If<=
br>
jsonpath argument is constant and all methods inside are safe then<br>
jsonb_path_query() is immutable otherwise it is stable.=C2=A0 I was<br>
thinking about that back working on jsonpath, but that time problem<br>
seemed too limited for this kind of solution.=C2=A0 Now, it&#39;s possibly =
time<br>
to shake off the dust from this idea.=C2=A0 What do you think?<br></blockqu=
ote><div><br></div><div>I was thinking about taking another stab at this.</=
div><div>Would someone more versed in the inner workings of jsonpath like t=
o weigh in on the immutability wrt locale?</div></div></div>

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