keith-turner commented on code in PR #5497:
URL: https://github.com/apache/accumulo/pull/5497#discussion_r2056276622
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server/tserver/src/main/java/org/apache/accumulo/tserver/log/LogSorter.java:
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@@ -274,12 +274,7 @@ void writeBuffer(String destPath,
List<Pair<LogFileKey,LogFileValue>> buffer, in
var logFileKey = pair.getFirst();
var logFileValue = pair.getSecond();
Key k = logFileKey.toKey();
- var list = keyListMap.putIfAbsent(k, logFileValue.mutations);
- if (list != null) {
- var muts = new ArrayList<>(list);
- muts.addAll(logFileValue.mutations);
- keyListMap.put(logFileKey.toKey(), muts);
- }
+ keyListMap.computeIfAbsent(k, (key) -> new
ArrayList<>()).addAll(logFileValue.mutations);
Review Comment:
Seems like this code was attempting to avoid any copy when the key was only
seen once. However when a key was seen more than once it would keep copying.
Wondering if we can efficiently accomplish the following in some way.
1. The first time a key is seen put a reference to the list in the map w/o
copy
2. The second time a key is seen, copy the list and then append
3. The third or later time a keys is seen append to list and do not copy.
I was able to create a test that reproduces this problem. Will post that in
another cmment and try this change w/ the test.
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