[prev in list] [next in list] [prev in thread] [next in thread]
List: postgresql-general
Subject: Re: [HACKERS] Nulls, arrays, records, IS NULL, IS DISTINCT FROM
From: Tom Lane <tgl () sss ! pgh ! pa ! us>
Date: 2006-09-29 17:24:15
Message-ID: 17789.1159550655 () sss ! pgh ! pa ! us
[Download RAW message or body]
David Fetter <david@fetter.org> writes:
> On Fri, Sep 29, 2006 at 12:53:19PM -0400, Tom Lane wrote:
>> In particular, the spec says
>> ROW(1,2,NULL) IS NOT NULL
>> is false, because the row fields must be *all* not null to make it true.
> That's odd because as I understand the above,
> ROW(1,2,NULL) IS NULL
> is also false. Have I misunderstood?
Yup, they are both false. The spec goes to some trouble to make it
clear that IS NULL/IS NOT NULL are not inverses for row values:
NOTE 135 - For all R, "R IS NOT NULL" has the same result as
"NOT R IS NULL" if and only if R is of degree 1. Table 16,
"<null predicate> semantics", specifies this behavior.
What I find odd is the lack of comparable language about arrays.
regards, tom lane
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
[prev in list] [next in list] [prev in thread] [next in thread]
Configure |
About |
News |
Add a list |
Sponsored by KoreLogic