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https://issues.apache.org/jira/browse/CALCITE-3878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17073380#comment-17073380
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neoremind commented on CALCITE-3878:
------------------------------------
[~julianhyde] Many thanks for your reply. I understand your concern and think
the solution makes sense. I update my PR to address your comment, my rationales
are:
1) Apply changes to where column fields or projections are needed, since
selection list size might bigger than 10.
2) Update a critical path in Prepare.java, since materializations is usually an
empty immutable list.
{code:java}
- final List<RelOptMaterialization> materializationList = new ArrayList<>();
+ final List<RelOptMaterialization> materializationList = new
ArrayList<>(materializations.size());
{code}
> 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: 1h 10m
> 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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