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https://issues.apache.org/jira/browse/NIFI-4836?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16351903#comment-16351903
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ASF GitHub Bot commented on NIFI-4836:
--------------------------------------
Github user MikeThomsen commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2447#discussion_r165860112
--- Diff:
nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/QueryDatabaseTable.java
---
@@ -315,6 +334,12 @@ public void onTrigger(final ProcessContext context,
final ProcessSessionFactory
session.getProvenanceReporter().receive(fileToProcess, jdbcURL,
stopWatch.getElapsed(TimeUnit.MILLISECONDS));
resultSetFlowFiles.add(fileToProcess);
+ // If we've reached the batch size, send out the
flow files
+ if (outputBatchSize > 0 &&
resultSetFlowFiles.size() >= outputBatchSize) {
+ session.transfer(resultSetFlowFiles,
REL_SUCCESS);
+ session.commit();
+ resultSetFlowFiles.clear();
--- End diff --
I usually reinitialize the collection in cases like this. I think in the
past I've had weird behavior from a collection when using clear() a lot on a
lot of referenced objects. Not a needed change and maybe that's paranoia on my
part based on weirdness from past projects.
> Allow QueryDatabaseTables to send out batches of flow files while result set
> is being processed
> -----------------------------------------------------------------------------------------------
>
> Key: NIFI-4836
> URL: https://issues.apache.org/jira/browse/NIFI-4836
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Extensions
> Reporter: Matt Burgess
> Assignee: Matt Burgess
> Priority: Major
>
> Currently QueryDatabaseTable (QDT) will not transfer the outgoing flowfiles
> to the downstream relationship(s) until the entire result set has been
> processed (regardless of whether Max Rows Per Flow File is set). This is so
> the maxvalue.* and fragment.count attributes can be set correctly for each
> flow file.
> However for very large result sets, the initial fetch can take a long time,
> and depending on the setting of Max Rows Per FlowFile, there could be a great
> number of FlowFiles transferred downstream as a large burst at the end of QDT
> execution.
> It would be nice for the user to be able to choose to have FlowFiles be
> transferred downstream while the result set is still being processed. This
> alleviates the "large burst at the end" by replacing it with smaller output
> batches during processing. The tradeoff will be that if an Output Batch Size
> is set, then the maxvalue.* and fragment.count attributes will not be set on
> the outgoing flow files.
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