Re: BUG #16368: Incorrect function inlining in the presence of awindow function
| От | David G. Johnston |
|---|---|
| Тема | Re: BUG #16368: Incorrect function inlining in the presence of awindow function |
| Дата | |
| Msg-id | CAKFQuwbBmEGw0hB6B3oMoWVaXjVHEziScqhz0d7FpiG6cBs0EQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | BUG #16368: Incorrect function inlining in the presence of a window function (PG Bug reporting form <noreply@postgresql.org>) |
| Ответы |
Re: BUG #16368: Incorrect function inlining in the presence of a window function
|
| Список | pgsql-bugs |
On Wed, Apr 15, 2020 at 11:07 AM PG Bug reporting form <noreply@postgresql.org> wrote:
The following bug has been logged on the website:
Bug reference: 16368
Logged by: Elvis Pranskevichus
Email address: elprans@gmail.com
PostgreSQL version: 12.2
Operating system: Gentoo Linux
Description:
Consider the following function:
CREATE OR REPLACE FUNCTION intfmt(input text, fmt text)
[...]
SELECT
CASE WHEN fmt IS NULL
THEN input::bigint
ELSE to_number(input, fmt)::bigint
END;
[...]
SELECT
[...]
intfmt('123,456', q.fmt) AS "out"
The expected result is the integer 123456, but the query fails with:
ERROR: invalid input syntax for type bigint: "123,456"
CONTEXT: SQL function "intfmt" during inlining
Which means that somehow during inlining of "intfmt" Postgres incorrectly
takes the first branch in the `CASE` expression.
During inlining the case expression becomes:
CASE WHEN q.fmt IS NULL
THEN '123,456'::bigint
ELSE to_number('123,456', q.fmt)
END;
It doesn't "take" a branch - it turns variables into constants and, as written, some of those constants are invalid for the types they are being assigned to.
This only happens in the
presence of the "first_value" window call in the nested query.
The ability to optimize, and how, depends on the whole query.
I don't actually know whether this is a bug or just an expected downside to using inline-able functions and case statements to avoid malformed data parsing.
Writing the function in pl/pgsql prevents the inlining and stabilizes the query.
David J.
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