zhuqi-lucas commented on issue #16193:
URL: https://github.com/apache/datafusion/issues/16193#issuecomment-2916070640
> Just for context, I ran into this while working on a Java based
application that drives the DataFusion queries. I want to be able to interrupt
query execution from the Java side. From the Java side I'm basically calling
`runtime.block_on(async { record_batch_stream.next().await })`. Since I can't
use Java's thread interruption mechanism to unblock the `next()` call I was
trying to use `tokio::select!` with a cancellation token instead and that
failed to cancel. This is the same pattern as what the CLI does, just triggered
via a different channel than a signal handler.
>
> I still need to write an experiment for this, but based on my reading of
the documentation even with a `RecordBatchReceiverStream` the aggregate would
not actually get cancelled. It will look like it has cancelled because the top
level task will yield, the `JoinSet` will get dropped, and the spawned tasks
will be aborted. But tokio will only actually be able to terminate the task
once the aggregate stream's poll loop yields.
Thank you @pepijnve for this info, i tried the aggregate with more than 1
partition, it seems can be canceled, and it uses RecordBatchReceiverStream
inside the CoalescePartitionExec, do you mean it's not the
RecordBatchReceiverStream which help the cancellation?
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