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
"never".
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?
Cheers,
Gavin
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