justinborromeo commented on a change in pull request #7024: Time Ordering
Option on Small-Result-Set Scan Queries
URL: https://github.com/apache/incubator-druid/pull/7024#discussion_r257435395
##########
File path:
processing/src/main/java/org/apache/druid/query/scan/ScanQueryQueryToolChest.java
##########
@@ -58,37 +68,64 @@ public ScanQueryQueryToolChest(
@Override
public QueryRunner<ScanResultValue> mergeResults(final
QueryRunner<ScanResultValue> runner)
{
- return new QueryRunner<ScanResultValue>()
- {
- @Override
- public Sequence<ScanResultValue> run(
- final QueryPlus<ScanResultValue> queryPlus, final Map<String,
Object> responseContext
- )
- {
- // Ensure "legacy" is a non-null value, such that all other nodes this
query is forwarded to will treat it
- // the same way, even if they have different default legacy values.
- final ScanQuery scanQuery = ((ScanQuery)
queryPlus.getQuery()).withNonNullLegacy(scanQueryConfig);
- final QueryPlus<ScanResultValue> queryPlusWithNonNullLegacy =
queryPlus.withQuery(scanQuery);
+ return (queryPlus, responseContext) -> {
+ // Ensure "legacy" is a non-null value, such that all other nodes this
query is forwarded to will treat it
+ // the same way, even if they have different default legacy values.
+ final ScanQuery scanQuery = ((ScanQuery)
queryPlus.getQuery()).withNonNullLegacy(scanQueryConfig);
+ final QueryPlus<ScanResultValue> queryPlusWithNonNullLegacy =
queryPlus.withQuery(scanQuery);
+ final BaseSequence.IteratorMaker scanQueryLimitRowIteratorMaker =
+ new BaseSequence.IteratorMaker<ScanResultValue,
ScanQueryLimitRowIterator>()
+ {
+ @Override
+ public ScanQueryLimitRowIterator make()
+ {
+ return new ScanQueryLimitRowIterator(runner,
queryPlusWithNonNullLegacy, responseContext);
+ }
+ @Override
+ public void cleanup(ScanQueryLimitRowIterator iterFromMake)
+ {
+ CloseQuietly.close(iterFromMake);
+ }
+ };
+
+ if (scanQuery.getTimeOrder().equals(ScanQuery.TIME_ORDER_NONE)) {
if (scanQuery.getLimit() == Long.MAX_VALUE) {
return runner.run(queryPlusWithNonNullLegacy, responseContext);
}
- return new BaseSequence<>(
- new BaseSequence.IteratorMaker<ScanResultValue,
ScanQueryLimitRowIterator>()
+ return new BaseSequence<ScanResultValue,
ScanQueryLimitRowIterator>(scanQueryLimitRowIteratorMaker);
+ } else if
((scanQuery.getTimeOrder().equals(ScanQuery.TIME_ORDER_ASCENDING) ||
+
scanQuery.getTimeOrder().equals(ScanQuery.TIME_ORDER_DESCENDING))
+ && scanQuery.getLimit() <=
scanQueryConfig.getMaxRowsTimeOrderedInMemory()) {
+ Iterator<ScanResultValue> scanResultIterator =
scanQueryLimitRowIteratorMaker.make();
Review comment:
Ah shoot, I misunderstood part of the issue. I wrote this under the
assumption that it would act like an ORDER BY operator. So if I understand
correctly now, this query:
```
{
...
"timeOrdering":"descending"
"limit":100
}
```
should return the latest 100 rows?
Conversely, this query:
```
{
...
"timeOrdering":"ascending"
"limit":100
}
```
should return the earliest 100 rows?
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