Re: logical column ordering

On 12/09/2014 06:19 PM, Josh Berkus wrote:
> On 12/09/2014 09:41 AM, Alvaro Herrera wrote:
>> The first thing where this matters is tuple descriptor expansion in
>> parse analysis; at this stage, things such as "*" (in "select *") are
>> turned into a target list, which must be sorted according to attlognum.
>> To achieve this I added a new routine to tupledescs,
> The two other major cases are:
>
> INSERT INTO table SELECT|VALUES ...
>
> COPY table FROM|TO ...
>
> ... although copy should just be a subclass of SELECT.
>
> Question on COPY, though: there's reasons why people would want COPY to
> dump in either physical or logical order. If you're doing COPY to
> create CSV files for output, then you want the columns in logical order.
> If you're doing COPY for pg_dump, then you want them in physical order
> for faster dump/reload. So we're almost certainly going to need to have
> an option for COPY.
>
>

I seriously doubt it, although I could be wrong. Unless someone can show
a significant performance gain from using physical order, which would be
a bit of a surprise to me, I would just stick with logical ordering as
the default.

cheers

andrew