[jira] [Comment Edited] (FLINK-32410) Allocate hash-based collections with sufficient capacity for expected size

["Matthias Pohl (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-32410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17810418#comment-17810418 ] 

Matthias Pohl edited comment on FLINK-32410 at 1/24/24 2:32 PM:
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[~srichter] is this an ongoing effort? Looks like the PR made it into master and release-1.18 with [ab9445ac|https://github.com/apache/flink/commit/ab9445ac] and we could set the fixVersion to 1.18.0 and close this issue?

I just came across it when investigating some test instability in 1.18


was (Author: mapohl):
[~srichter] is this an ongoing effort? Looks like the PR made it into master and release-1.18 with [ab9445ac|https://github.com/apache/flink/commit/ab9445ac] and we could set the fixVersion to 1.18.0 and close this issue?

> Allocate hash-based collections with sufficient capacity for expected size
> --------------------------------------------------------------------------
>
>                 Key: FLINK-32410
>                 URL: https://issues.apache.org/jira/browse/FLINK-32410
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: Stefan Richter
>            Assignee: Stefan Richter
>            Priority: Major
>              Labels: pull-request-available, stale-assigned
>             Fix For: 1.19.0
>
>
> The JDK API to create hash-based collections for a certain capacity is arguable misleading because it doesn't size the collections to "hold a specific number of items" like you'd expect it would. Instead it sizes it to hold load-factor% of the specified number.
> For the common pattern to allocate a hash-based collection with the size of expected elements to avoid rehashes, this means that a rehash is essentially guaranteed.
> We should introduce helper methods (similar to Guava's `Maps.newHashMapWithExpectedSize(int)`) for allocations for expected size and replace  the direct constructor calls with those.



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