On 9/9/15 7:55 PM, Charles Sheridan wrote:
The better question is how expensive is it to sort already sorted data. If its cheap, and it likely is, then placing explicit sorting where you care is the best solution regardless of your level of confidence that lower level sorting is being maintained.
...
David, yes, I agree that sorting at the end is the highest-confidence approach. I don't (yet) have a large stack of views with an assumption of a guaranteed underlying sort order, I'm just trying to get a better sense of what Postgres behavior I can reasonably expect here.
BTW, I believe there is some code in the planner to remove useless ORDER-BYs.
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