Re: Bug in jsonb_path_exists (maybe _match) one-element scalar/variable jsonpath handling
| От | David G. Johnston |
|---|---|
| Тема | Re: Bug in jsonb_path_exists (maybe _match) one-element scalar/variable jsonpath handling |
| Дата | |
| Msg-id | CAKFQuwbRpF2bpSORTUqZW1rAonMyPjT_3RoGmqzPpr8rE9hyYQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Bug in jsonb_path_exists (maybe _match) one-element scalar/variable jsonpath handling (Alexander Korotkov <aekorotkov@gmail.com>) |
| Ответы |
Re: Bug in jsonb_path_exists (maybe _match) one-element scalar/variable jsonpath handling
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| Список | pgsql-bugs |
On Fri, Dec 2, 2022 at 10:47 AM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> Thank you for explaining your point, but I can't agree with that.
> Constant jsonpath expression is always returning item for the input
> JSON value. Even despite the input value is ignored. This is
> redundant case, but still correct.
Let me explain more what I do mean. In the SQL SELECT statement there
is a WHERE clause. This clause should express the predicate, which
should match to rows. But you're writing "WHERE 1 = 1" or "WHERE
true" then all rows are matching even that no column is referenced.
This is how SQL is working. And I see no reason why jsonpath should
work in a different way.
I like the analogy but it seems to support my conclusion moreso than yours:
Consider: select jsonb_path_exists('{"foo":"bar"}'::jsonb, 'false');
The analogous SQL query is: "SELECT * FROM table WHERE false" would indeed produce an empty set - which EXISTS would interpret as false but you want to evaluate to true
Or, "SELECT * FROM table WHERE 'banana';" which produces the same kind of error that I wish jsonb_path_exists would produce when one writes a similarly nonsensical path.
David J.
I'll probably get to a formal review of the patch - but actually I am hoping someone else more comfortable in the codebase chimes in here with an opinion. Though as I said, I'm willing to concede that the behavior should probably stay unchanged, for compatibility reasons, and we just need to decide on how to correctly document this.
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