jtuglu-netflix commented on code in PR #17847:
URL: https://github.com/apache/druid/pull/17847#discussion_r2067129281
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server/src/main/java/org/apache/druid/segment/realtime/appenderator/StreamAppenderator.java:
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@@ -354,40 +376,43 @@ public AppenderatorAddResult add(
boolean isPersistRequired = false;
boolean persist = false;
- List<String> persistReasons = new ArrayList<>();
+ final String[] persistReasons = new String[NUMBER_OF_PERSIST_REASONS];
Review Comment:
Yeah. In c++ std::array is guaranteed stack allocation whereas the resizable
equivalent is heap-based (slower). I guess in Java this distinction isn't as
stark since you can't actually control where the memory is allocated. The
difference showed up in the profile, but:
> The downside of using arrays is that future maintainers will have to
resize the array when they want to add reasons.
We can leave for now due to this^
##########
server/src/main/java/org/apache/druid/segment/realtime/appenderator/StreamAppenderator.java:
##########
@@ -354,40 +376,43 @@ public AppenderatorAddResult add(
boolean isPersistRequired = false;
boolean persist = false;
- List<String> persistReasons = new ArrayList<>();
+ final String[] persistReasons = new String[NUMBER_OF_PERSIST_REASONS];
Review Comment:
Yeah. In c++ std::array is guaranteed stack allocation whereas the resizable
equivalent vector is heap-based (slower). I guess in Java this distinction
isn't as stark since you can't actually control where the memory is allocated.
The difference showed up in the profile, but:
> The downside of using arrays is that future maintainers will have to
resize the array when they want to add reasons.
We can leave for now due to this^
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