[BUGS] BUG #8141: multi-column check expression evaluating to NULL
The following bug has been logged on the website: Bug reference: 8141 Logged by: Andras Vaczi Email address: andras.va...@zalando.de PostgreSQL version: 9.1.9 Operating system: linux/Ubuntu 12.10 Description: Consider the following table with a CHECK constraint: CREATE TABLE check_test ( id integer NOT NULL, col integer, CONSTRAINT unique_with_null_check1 CHECK (col = 1 AND id 20) ); This INSERT statement succeeds: INSERT INTO check_test (id, col) VALUES (1, NULL); While, col being NULL, the whole CHECK condition evaluates to NULL - this is covered in the documentation. But this is refused: INSERT INTO check_test (id, col) VALUES (21, NULL); ERROR: new row for relation check_test violates check constraint unique_with_null_check1 I think this behaviour should be either also mentioned in the docs or cosidered a bug. -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
Re: [BUGS] BUG #8141: multi-column check expression evaluating to NULL
andras.va...@zalando.de writes: Consider the following table with a CHECK constraint: CREATE TABLE check_test ( id integer NOT NULL, col integer, CONSTRAINT unique_with_null_check1 CHECK (col = 1 AND id 20) ); This INSERT statement succeeds: INSERT INTO check_test (id, col) VALUES (1, NULL); While, col being NULL, the whole CHECK condition evaluates to NULL - this is covered in the documentation. But this is refused: INSERT INTO check_test (id, col) VALUES (21, NULL); ERROR: new row for relation check_test violates check constraint unique_with_null_check1 I think this behaviour should be either also mentioned in the docs or cosidered a bug. I see no bug here. In the first case, the col = 1 condition yields NULL while id 20 yields TRUE, so you have NULL AND TRUE which is NULL, which is considered a pass for a CHECK condition per spec. In the second case, col = 1 is still NULL, but id 20 is FALSE, so you have NULL AND FALSE which is FALSE (*not* NULL), and so failure is per spec. Yes, the behavior of AND/OR with NULLs is documented. http://www.postgresql.org/docs/9.1/static/functions-logical.html regards, tom lane -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
Re: [BUGS] BUG #8141: multi-column check expression evaluating to NULL
On 09/05/13 01:07, andras.va...@zalando.de wrote: The following bug has been logged on the website: Bug reference: 8141 Logged by: Andras Vaczi Email address: andras.va...@zalando.de PostgreSQL version: 9.1.9 Operating system: linux/Ubuntu 12.10 Description: Consider the following table with a CHECK constraint: CREATE TABLE check_test ( id integer NOT NULL, col integer, CONSTRAINT unique_with_null_check1 CHECK (col = 1 AND id 20) ); [...] if 'id' is the primary key, then the table should be defined as: CREATE TABLE check_test ( id integer PRIMARY KEY, col integer NOT NULL, CONSTRAINT unique_with_null_check1 CHECK (col = 1 AND id 20) ); Because: 1. 'PRIMARY KEY ' implies 'NOT NULL' and also 'UNIQUE', and so an index is created for 'id' (index is required to enforce uniqueness) 2. you are testing that 'col' has a certain type of numeric value, so this logically implies that it is 'NON NULL', but you actually have to tell progress explicitly tat you want it to be 'NON NULL' Cheers, Gavin