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https://issues.apache.org/jira/browse/FLINK-13236?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-13236:
-----------------------------------
Labels: pull-request-available (was: )
> Fix bug and improve performance in TopNBuffer
> ---------------------------------------------
>
> Key: FLINK-13236
> URL: https://issues.apache.org/jira/browse/FLINK-13236
> Project: Flink
> Issue Type: Improvement
> Reporter: Caizhi Weng
> Assignee: Caizhi Weng
> Priority: Minor
> Labels: pull-request-available
>
> In {{TopNBuffer}} we have the following method:
> {code:java}
> /**
> * Puts a record list into the buffer under the sortKey.
> * Note: if buffer already contains sortKey, putAll will overwrite the
> previous value
> *
> * @param sortKey sort key with which the specified values are to be
> associated
> * @param values record lists to be associated with the specified key
> */
> void putAll(BaseRow sortKey, Collection<BaseRow> values) {
> treeMap.put(sortKey, values);
> currentTopNum += values.size();
> }
> {code}
> When {{sortKey}} already exists in {{treeMap}}, the {{currentTopNum}} should
> be first subtracted by the old {{value.size()}} in {{treeMap}} then added
> (can't be directly added). As currently only {{AppendOnlyTopNFunction}} uses
> this method in its init procedure, this bug is not triggered.
> {code:java}
> /**
> * Gets record which rank is given value.
> *
> * @param rank rank value to search
> * @return the record which rank is given value
> */
> BaseRow getElement(int rank) {
> int curRank = 0;
> Iterator<Map.Entry<BaseRow, Collection<BaseRow>>> iter =
> treeMap.entrySet().iterator();
> while (iter.hasNext()) {
> Map.Entry<BaseRow, Collection<BaseRow>> entry = iter.next();
> Collection<BaseRow> list = entry.getValue();
> Iterator<BaseRow> listIter = list.iterator();
> while (listIter.hasNext()) {
> BaseRow elem = listIter.next();
> curRank += 1;
> if (curRank == rank) {
> return elem;
> }
> }
> }
> return null;
> }
> {code}
> We can remove the inner loop by adding {{curRank}} by {{list.size()}} each
> time.
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