claudeyj commented on code in PR #10445:
URL: https://github.com/apache/pinot/pull/10445#discussion_r1141639727
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pinot-segment-local/src/main/java/org/apache/pinot/segment/local/segment/creator/impl/SegmentIndexCreationDriverImpl.java:
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@@ -175,7 +175,7 @@ public void init(SegmentGeneratorConfig config,
SegmentCreationDataSource dataSo
// Initialize index creation
_segmentIndexCreationInfo = new SegmentIndexCreationInfo();
- _indexCreationInfoMap = new HashMap<>();
+ _indexCreationInfoMap = new LinkedHashMap<>();
Review Comment:
I think you refer to the cost of `Map.put(key, value)` (the index creation),
so I run some simple profiling experiments in my machine. I just iterate for
many times and invoke the `put` method. It shows that with iterations ranging
from 1000 to 10,000,000, the time consumption for HashMap and LinkedHashMap is
respecitively (1ms, 1ms), (4ms, 5ms), (33ms, 17ms), (138ms, 115ms), (1647ms,
3006ms), (114668ms, 33698ms). You can see the performance difference is quite
related to number of iterations. In this case the key of two maps affected is
`columnName` and I'm not sure about the normal number of columns in realistic
scenario but hope this can help you do the trade off.
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