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https://issues.apache.org/jira/browse/HIVE-20509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16612987#comment-16612987
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Gopal V commented on HIVE-20509:
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[~b.maidics]: You are right, my calculation is wrong - I'm assuming the whole
entry can be skipped (so 72 is what we save).
However, now that I think about it a bit more, I can't see why we end up with
thousands of identical arraylist objects - we can generate default 1 element
list for each alias with a CopyOnWriteArrayList() & save more space for large
partitioned tables.
> Plan: fix wasted memory in plans with large partition counts
> ------------------------------------------------------------
>
> Key: HIVE-20509
> URL: https://issues.apache.org/jira/browse/HIVE-20509
> Project: Hive
> Issue Type: Bug
> Components: Query Planning
> Reporter: Gopal V
> Assignee: Barnabas Maidics
> Priority: Minor
> Labels: newbie
> Attachments: HIVE-20509.2.patch, HIVE-20509.patch, after.png,
> before.png
>
>
> {code}
> public void addPathToAlias(Path path, String newAlias){
> ArrayList<String> aliases = pathToAliases.get(path);
> if (aliases == null) {
> aliases = new ArrayList<>();
> StringInternUtils.internUriStringsInPath(path);
> pathToAliases.put(path, aliases);
> }
> aliases.add(newAlias.intern());
> }
> {code}
> ArrayList::DEFAULT_CAPACITY is 10, so this wastes 500 bytes of memory due to
> the {{new ArrayList<>();}}.
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