Simon Riggs wrote:
On Fri, 2007-02-23 at 11:25 +0100, Peter Eisentraut wrote:
Am Freitag, 23. Februar 2007 09:08 schrieb Simon Riggs:
If this is standards-breaking as you say, I would withdraw immediately.
I checked the SQL standard and could not see how this would do so. The
standard states SELECT * would return columns in order; it doesn't say
what that order should be,
b) Otherwise, the <select list> “*” is equivalent to a <value expression>
sequence in which each <value expression> is a column reference that
references a column of T and each column of T is referenced exactly once. The
columns are referenced in the ascending sequence of their ordinal position
within T.
Which begs the question: what is their ordinal position? If we change
the ordinal position at CREATE TABLE time then the SELECT * would still
work per standard.
That's quite a stretch. Surely "their ordinal position" can't mean
"their ordinal position as arbitrarily determined at CREATE TABLE time
by the implementation".
I really don't think that we can accept under any circumstances a
situation where something as simple as this breaks:
create table foo (x text, y int);
insert into foo values ('qwerty',1);
Physical storage optimization must not have any SQL level visibility or
consequences, IMNSHO, regardless of what we do about providing mutable
display order.
If you really want an interim solution, what about a builtin function
that would explicitly mutate the definition and table contents (if any)
along the lines you want? (assuming that's lots less work than just
doing the whole thing right to start with). Or even one which just
*displayed* the optimal order might be sufficient assistance to DBAs who
want to take advantage of this.
cheers
andrew
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