Re: UPDATE... FROM - will ORDER BY not respected?

Carlo Stonebanks wrote:
>> I think the ORDER BY is free to update the rows in any order it needs
>> to.  The key is to put the sequence further down.  How about this?
>
> Adam - thanks. Unless I hear otherwise I will assume that you mean the
> UPDATE is free to update the rows in any way it wants - irregardless of
> how whether the data return in the FROM clause is ordered.
>

Whoops - you're right, that's what I meant.  Even though one of the
tables is sorted, when it joins the two tables, the planner might decide
it's cheaper to update impt_table by iteratively looking up values from
the sorted table that match the (unordered) rows from impt_table, or
by hashing the keys which I think also results in unsorted updates.
You can use "explain" to see the details.

Adam