colexec: fix coalescing logic in the spilling queue #59057
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In a recently merged change to the spilling queue we introduced a bug in the coalescing logic - we incorrectly computed the index of the "tail" batch in case when it is the last one in the in-memory buffer. This could lead to multiple problems (modification of the filled-up batch, of the already dequeued batch, etc). This is now fixed. Additionally, this commit switches to using `Copy` instead of `Append` in that coalescing logic (since we know that there is enough capacity for all of the tuples we're appending) and sets the item to `nil` when it was dequeued. Release note: None (no stable release with this bug)
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asubiotto
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Jan 15, 2021
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complete! 0 of 0 LGTMs obtained (waiting on @yuzefovich)
pkg/sql/colexec/spilling_queue.go, line 245 at r1 (raw file):
tailBatchIdx := q.curTailIdx - 1 if tailBatchIdx < 0 { tailBatchIdx = len(q.items) - 1
Added a comment about adding a unit test in the other PR.
asubiotto
approved these changes
Jan 15, 2021
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Actually, I was wrong - the simple unit test I had in mind doesn't trigger the bug since in order for it to surface a careful coordination of enqueues and dequeues is required, so I'll go ahead and merge as is and will add a test in a follow-up. TFTR! bors r+ |
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In a recently merged change to the spilling queue we introduced a bug in
the coalescing logic - we incorrectly computed the index of the "tail"
batch in case when it is the last one in the in-memory buffer. This
could lead to multiple problems (modification of the filled-up batch, of
the already dequeued batch, etc). This is now fixed.
Additionally, this commit switches to using
Copyinstead ofAppendin that coalescing logic (since we know that there is enough capacity
for all of the tuples we're appending) and sets the item to
nilwhenit was dequeued.
Addresses: #47652.
Fixes: #58913.
Fixes: #58915.
Fixes: #58934.
Fixes: #58935.
Fixes: #58936.
Fixes: #58956.
Release note: None (no stable release with this bug)