From: PG Bug reporting form <noreply@postgresql.org>
To: pgsql-bugs@lists.postgresql.org
Cc: arthur.mcgibbon@gmail.com
Subject: BUG #17052: Incorrect params inferred on PREPARE (part 2)
Date: Tue, 08 Jun 2021 11:27:51 +0000
Message-ID: <17052-0bb053c08bb80fb6@postgresql.org> (raw)
The following bug has been logged on the website:
Bug reference: 17052
Logged by: Arthur McGibbon
Email address: arthur.mcgibbon@gmail.com
PostgreSQL version: 13.3
Operating system: Windows + wsl2 + docker
Description:
Using the table...
CREATE TABLE testSchema.testTable (timestampCol timestamp);
...and preparing the query...
PREPARE testQuery (unknown) AS
UPDATE testSchema.testTable
SET timestampCol = $1 + interval '1 minute';
...results in an error...
ERROR: column "timestampcol" is of type timestamp without time zone but
expression is of type interval
LINE 4: set timestampCol = $1 + interval '1 minute';
^
HINT: You will need to rewrite or cast the expression.
SQL state: 42804
Character: 82
Specifying the parameter as timestamp works without error...
PREPARE testQuery (timestamp) AS
UPDATE testSchema.testTable
SET timestampCol = $1 + interval '1 minute';
as does casting...
PREPARE testQuery (unknown) AS
UPDATE testSchema.testTable
SET timestampCol = cast($1 as timestamp) + interval '1 minute';
I'd hope that PostgreSQL would infer a "timestamp" type here instead of an
interval type
It seems in this case (and possibly in bug report 17051) Postgres uses only
a section of the expression to evaluate the parameter type i.e. "$1 +
interval '1 minute'" and assumes that only an interval type can be added to
an interval type but there are a number of types that can be added to an
interval type and ideally it would take into account the result of the
expression which has to be a timestamp (because of the definition of the
timestampCol column) and so work out that the only (or best) way to achieve
that is to have $1 be of type timestamp.
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To: pgsql-bugs@postgresql.org
Cc: noreply@postgresql.org, pgsql-bugs@lists.postgresql.org, arthur.mcgibbon@gmail.com
Subject: Re: BUG #17052: Incorrect params inferred on PREPARE (part 2)
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