Re: ORDER BY and NULLs

Hello,

Greg Stark wrote:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>
>
>>>The paragraph continues:
>>>"If the SELECT command included the clause WHERE phone NOT NULL,
>>>PostgreSQL could use the index to satisfy the ORDER BY clause.
>>>An index that covers optional (NOT NULL) columns will not be used to
>>>speed table joins either."
>>
>>My goodness, it seems to be a veritable fount of misinformation :-(
>>

> I wonder if they just tried explain on a bunch of queries and noticed that
> postgres wasn't using an index for SELECT * FROM foo ORDER BY bar and came up
> with explanations for the patterns they saw?

This paragraph was in the chapter about PostgreSQL indexing and the
paragraph itself was entitled "Indexes and Null values".

--

Regards/Gruß,

Tarlika Elisabeth Schmitz