fix: substrait limit when fetch is None #7669
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Signed-off-by: Ruihang Xia <waynestxia@gmail.com>
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Sep 28, 2023
| @@ -442,7 +442,7 @@ impl LimitStream { | |||
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| match &poll { | |||
| Poll::Ready(Some(Ok(batch))) => { | |||
| if batch.num_rows() > 0 && self.skip == 0 { | |||
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Is the rationale that this condition is redundant because any batch with zero rows will also have self.skip equal to zero?
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Yes. To my understanding these two conditions are identical. So I removed one to make it simpler
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Oct 7, 2023
* fix: substrait limit when fetch is None Signed-off-by: Ruihang Xia <waynestxia@gmail.com> * Add comments --------- Signed-off-by: Ruihang Xia <waynestxia@gmail.com> Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>
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Which issue does this PR close?
related to GreptimeTeam/greptimedb#2495
Rationale for this change
I found the producer will replace
fetch = Nonewithfetch = 0, and consumer will always putSomein the position of fetch. This is incorrect for query withoutLIMIT, e.g.:SELECT * FROM t OFFSET 1What changes are included in this PR?
Fix the bug. As substrait cannot express
None, I useusize::MAXto representNonein producer, and convert it back toNonein consumer.This patch also has a minor change in
LimitExec. I thought that condition was redundant so I removed it.Are these changes tested?
I add a new round trip case
Are there any user-facing changes?
No