| Lists: | pgsql-hackers |
|---|
| From: | Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com> |
|---|---|
| To: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Overlap operators for ARRAY and NULLs |
| Date: | 2010-11-17 11:33:55 |
| Message-ID: | AANLkTikL_DRkvwWPtigkR-UU-f5+Et_XDdJU+C7XLX7z@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Lists: | pgsql-hackers |
There might be inconsistency in overlap operators for array
types ( <@, @>, and && ) when the argument arrays contain NULLs.
- SELECT 2 = ANY (ARRAY[1, NULL]) => NULL
- SELECT ARRAY[2] <@ ARRAY[1, NULL] => false
NULL means "unknown" in definition, so should it return NULL
rather than false?
I found the issue when I read spec of MULTISET. In the SQL
standard, the following expression returns NULL. I was thinking
to make SUBMULTISET OF to be an alias of <@ operator, but
they seems to be incompatible.
- MULTISET[2] SUBMULTISET OF MULTISET[1, NULL] => NULL
Will we change the operator's behavior? It would be more
consistent, but incompatible with older server versions.
If impossible, I'll add separated submultiset_of() function
instead of <@ operator for MULTISET supports.
--
Itagaki Takahiro
| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Overlap operators for ARRAY and NULLs |
| Date: | 2011-03-10 21:16:07 |
| Message-ID: | 201103102116.p2ALG7N10878@momjian.us |
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| Lists: | pgsql-hackers |
I have added a link to this from the exiting TODO item:
Improve handling of NULLs in arrays
* BUG #4509: array_cat's null behaviour is inconsistent
* http://archives.postgresql.org/pgsql-hackers/2010-11/msg01040.php
---------------------------------------------------------------------------
Itagaki Takahiro wrote:
> There might be inconsistency in overlap operators for array
> types ( <@, @>, and && ) when the argument arrays contain NULLs.
>
> - SELECT 2 = ANY (ARRAY[1, NULL]) => NULL
> - SELECT ARRAY[2] <@ ARRAY[1, NULL] => false
>
> NULL means "unknown" in definition, so should it return NULL
> rather than false?
>
> I found the issue when I read spec of MULTISET. In the SQL
> standard, the following expression returns NULL. I was thinking
> to make SUBMULTISET OF to be an alias of <@ operator, but
> they seems to be incompatible.
>
> - MULTISET[2] SUBMULTISET OF MULTISET[1, NULL] => NULL
>
> Will we change the operator's behavior? It would be more
> consistent, but incompatible with older server versions.
> If impossible, I'll add separated submultiset_of() function
> instead of <@ operator for MULTISET supports.
>
> --
> Itagaki Takahiro
>
> --
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> To make changes to your subscription:
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--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +