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https://issues.apache.org/jira/browse/CALCITE-3878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17068397#comment-17068397
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Feng Zhu commented on CALCITE-3878:
-----------------------------------
Certainly, changes made by this PR can help to improve the performance.
But from personal feeling, I'm just *-0* on this direction.
The optimization is a little nitpicking, and brings me some considerations on
code style and project evolution.
E.g., Should we document this pattern as a mandatory style? If not, how to cope
with the later contributions?
For example, after reviewing this PR, I noticed another PR
(https://github.com/apache/calcite/pull/1870), which uses "new ArrayList<>()"
but LGTM.
> Make ArrayList creation with initial capacity when size is fixed
> ----------------------------------------------------------------
>
> Key: CALCITE-3878
> URL: https://issues.apache.org/jira/browse/CALCITE-3878
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.22.0
> Reporter: neoremind
> Priority: Minor
> Labels: pull-request-available
> Time Spent: 40m
> Remaining Estimate: 0h
>
> I find many places in Calcite where _new ArrayList<>()_ is used, if the list
> is expected to be immutable or not resizing, it is always a good manner to
> create with initial capacity, better for memory usage and performance.
> I search all occurrences, focus on the core module, to make it safe, I only
> update local variables with fixed size and not working in recursive method.
> If the local variable reference goes out of scope, if resizing is needed,
> things will work normally as well, so no side effect, but for the "escaping"
> case, I am very conservative and do not change them.
>
>
>
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