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From: Mark Dilger <[email protected]>
To: Alexandra Wang <[email protected]>
Cc: Matheus Alcantara <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: Andrew Dunstan <[email protected]>
Cc: Nikita Glukhov <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: David E. Wheeler <[email protected]>
Cc: jian he <[email protected]>
Subject: Re: SQL:2023 JSON simplified accessor support
Date: Tue, 4 Mar 2025 07:34:53 -0800
Message-ID: <CAHgHdKubGHcJiZ6iVoBty5FwF4f+3uE0M00Er4tTsh4_LaH_xw@mail.gmail.com> (raw)
In-Reply-To: <CAHgHdKtL9nNaKXGCLt9gWugVzYWKhoBDQ7NESUwdCBty8kFK-A@mail.gmail.com>
References: <[email protected]>
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On Tue, Mar 4, 2025 at 6:05 AM Mark Dilger <[email protected]>
wrote:

> But then I tried:
>
> +DO $$
> +DECLARE
> +  a jsonb := '{"": 6, "NU": [{"": [[3]]}, [6], [2], "bCi"], "aaf": [-6,
> -8]}'::jsonb;
> +BEGIN
> +  WHILE a IS NOT NULL
> +  LOOP
> +    RAISE NOTICE '%', a;
> +    a := COALESCE(a."NU", a[2]);
> +  END LOOP;
> +END
> +$$ LANGUAGE plpgsql;
> +NOTICE:  {"": 6, "NU": [{"": [[3]]}, [6], [2], "bCi"], "aaf": [-6, -8]}
> +ERROR:  missing FROM-clause entry for table "a"
> +LINE 1: a := COALESCE(a."NU", a[2])
> +                      ^
> +QUERY:  a := COALESCE(a."NU", a[2])
> +CONTEXT:  PL/pgSQL function inline_code_block line 8 at assignment
>
> which suggests the plpgsql parser does not recognize a."NU" as we'd
> expect.  Any thoughts on this?
>

I should mention that

+DO $$
+DECLARE
+  a jsonb := '{"": 6, "NU": [{"": [[3]]}, [6], [2], "bCi"], "aaf": [-6,
-8]}'::jsonb;
+BEGIN
+  WHILE a IS NOT NULL
+  LOOP
+    RAISE NOTICE '%', a;
+    a := COALESCE((a)."NU", (a)[2]);
+  END LOOP;
+END
+$$ LANGUAGE plpgsql;
+NOTICE:  {"": 6, "NU": [{"": [[3]]}, [6], [2], "bCi"], "aaf": [-6, -8]}
+NOTICE:  [{"": [[3]]}, [6], [2], "bCi"]
+NOTICE:  [2]

works fine.  I guess that is good enough.  Should we add these to the
sql/jsonb.sql to document the expected behavior, both with the error when
using plain "a" and with the correct output when using "(a)"?  The reason I
mention this is that the plpgsql parser might get changed at some point,
and without a test case, we might not notice if this breaks.

—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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