On 30/04/17 16:28, Tom Lane wrote:
Craig Ringer <craig.rin...@2ndquadrant.com> writes:
- as you noted, it is hard to decide when it's worth inlining vs
materializing for CTE terms referenced more than once.
[ raised eyebrow... ]  Please explain why the answer isn't trivially

There's already a pretty large hill to climb here in the way of
breaking peoples' expectations about CTEs being optimization
fences.  Breaking the documented semantics about CTEs being
single-evaluation seems to me to be an absolute non-starter.

                        regards, tom lane

Could not each CTE be only evaluated once, but restricted (as far as is practicable) to the rows actually needed by the body of the SELECT?


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