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* jsonb subscript operator returns null when key is fetched from table
@ 2022-12-09 20:06 exe-dealer <exe-dealer@yandex.ru>
0 siblings, 1 reply; 3+ messages in thread
From: exe-dealer @ 2022-12-09 20:06 UTC (permalink / raw)
To: pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
<div><div><div>jsonb subscript operator returns null when key is fetched from table.</div><div> </div></div><div>PostgreSQL 15.1 on x86_64-pc-linux-musl, compiled by gcc (Alpine 12.2.1_git20220924-r4) 12.2.1 20220924, 64-bit</div><div> </div><div><span style="font-family:'courier new' , monospace">WITH cte AS MATERIALIZED (SELECT 'foo' k, '{"foo":"bar"}'::jsonb j)</span></div><div><span style="font-family:'courier new' , monospace">SELECT j[k], j[k || ''] FROM cte;</span></div><div> </div><div>-- returns</div><div>-- null, "bar"</div><div> </div><div>-- expected</div><div>-- "bar", "bar"</div><div> </div></div>
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: jsonb subscript operator returns null when key is fetched from table
@ 2022-12-12 18:51 David G. Johnston <david.g.johnston@gmail.com>
parent: exe-dealer <exe-dealer@yandex.ru>
0 siblings, 1 reply; 3+ messages in thread
From: David G. Johnston @ 2022-12-12 18:51 UTC (permalink / raw)
To: exe-dealer <exe-dealer@yandex.ru>; +Cc: pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
On Fri, Dec 9, 2022 at 1:35 PM exe-dealer <exe-dealer@yandex.ru> wrote:
> jsonb subscript operator returns null when key is fetched from table.
>
> PostgreSQL 15.1 on x86_64-pc-linux-musl, compiled by gcc (Alpine
> 12.2.1_git20220924-r4) 12.2.1 20220924, 64-bit
>
> WITH cte AS MATERIALIZED (SELECT 'foo' k, '{"foo":"bar"}'::jsonb j)
> SELECT j[k], j[k || ''] FROM cte;
>
> -- returns
> -- null, "bar"
>
> -- expected
> -- "bar", "bar"
>
Thanks for the report. I can confirm that this is a problem in both v14
and v15.
To clarify the subject line - the issue manifests only if the CTE is
MATERIALIZED.
Someone more experienced than I will need to actually do the debugging work
though; hoping this reply will be seen by one of them.
David J.
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: jsonb subscript operator returns null when key is fetched from table
@ 2022-12-12 19:09 Tom Lane <tgl@sss.pgh.pa.us>
parent: David G. Johnston <david.g.johnston@gmail.com>
0 siblings, 0 replies; 3+ messages in thread
From: Tom Lane @ 2022-12-12 19:09 UTC (permalink / raw)
To: David G. Johnston <david.g.johnston@gmail.com>; +Cc: exe-dealer <exe-dealer@yandex.ru>; pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
"David G. Johnston" <david.g.johnston@gmail.com> writes:
> Someone more experienced than I will need to actually do the debugging work
> though; hoping this reply will be seen by one of them.
Meh. Somebody was cavalier about detoasting the subscript:
jbvp = getKeyJsonValueFromContainer(container,
VARDATA(path[i]),
VARSIZE(path[i]) - VARHDRSZ,
NULL);
Neither VARDATA nor VARSIZE are valid to apply to an arbitrary datum.
Apparently, nobody has ever tested this with a subscript value fetched
straight from disk :-(. The given example accidentally works with
a NOT MATERIALIZED CTE because the whole thing gets stepwise folded
to constants. Likewise, the expression with || accidentally works
because concatenation always yields a non-toasted result.
regards, tom lane
^ permalink raw reply [nested|flat] 3+ messages in thread
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2022-12-09 20:06 jsonb subscript operator returns null when key is fetched from table exe-dealer <exe-dealer@yandex.ru>
2022-12-12 18:51 ` David G. Johnston <david.g.johnston@gmail.com>
2022-12-12 19:09 ` Tom Lane <tgl@sss.pgh.pa.us>
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