feat: support sequential exchange #14795
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It changes the memory usage from |
src/batch/src/task/task_execution.rs
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| impl Drop for TaskOutput { | ||
| fn drop(&mut self) { | ||
| println!("drop TaskOutput {:?}", self.output_id); | ||
| } | ||
| } |
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Previously, for small limit queries, this struct could not be dropped timely.
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Under a constant workload of limit queries. It could cause a OOM.
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Interesting, maybe we can use this test to check why task leak happens. Let me take a look later.
CN oom, I think it is related to the early stop of the limit execution. |
Let's take a look at the sysbench. |
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Are we sure this is the cause? Please at least run a sysbench test to verify it before merging. |
+1 |
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We'd better identify the root cause of the regression before applying any other optimizations to avoid getting things more complicated. 🥺 |
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Previous CN memory: 
Heap dump of the OOM: |
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After this PR: 
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It has achieved 300% performance improvement and much more stable memory consumption under this workload. |
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The root cause is small limit queries would fire more tasks as needed in the exchange operators, but when the limit query is ended, those fired tasks cannot be |
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This issue reminds me of the backfill prefetch streaming read OOM issue. Both of them share the same behavior. |
| while let Some(data_chunk) = stream.next().await { | ||
| let data_chunk = data_chunk?; | ||
| yield data_chunk | ||
| let streams = self |
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How about move this part to the self.sequential block? It's not easy to understand the difference of collection.
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What's changed and what's your intention?
Checklist
./risedev check(or alias,./risedev c)Documentation
Release note
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