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https://issues.apache.org/jira/browse/CALCITE-1227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15308626#comment-15308626
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Julian Hyde commented on CALCITE-1227:
--------------------------------------
I agree about the "upon next record" problem. That is why I suggested, a couple
of comments back, that the reader reads using a timeout. I notice that
CsvStreamReader has a field {{Queue<String> contentQueue}} and calls
{{contentQueue.poll();}}. Can you convert that to a {{BlockingQueue}} and call
{{BlockingQueue.poll(long timeout, TimeUnit unit)}}?
You could add
{code}
enum DataContext.Variable {
CANCEL_FLAG("cancelFlag", CancelFlag.class)
}
{code}
and the enumerator could check its state periodically:
{code}
DataContext root;
CancelFlag flag = root.get(DataContext.Variable.CANCEL_FLAG.name());
for (;;) {
...
if (flag.isCancelRequested()) {
return;
}
}
{code}
> Add streaming CSV table
> -----------------------
>
> Key: CALCITE-1227
> URL: https://issues.apache.org/jira/browse/CALCITE-1227
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
>
> Add a variant of CsvTable that can be streamed. It would serve as an example
> of how to write stream adapters.
> It would be like the CSV adapter, but watches a file and reports records
> added to the end of the file (like the tail command).
> You’d have to change {{CsvTable}} to implement {{StreamableTable}}, and
> implement the {{Table stream()}} method to return a variant of the table that
> is in “follow” mode.
> It would probably be implemented by a variant of CsvEnumerator, but it is
> getting its input in bursts, as the file is appended to.
> You would still be able to use this adapter to read historical data from the
> CSV file. Appending records to the file would make a nice demo.
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