[jira] [Updated] (HIVE-22414) Make LLAP CacheTags more memory efficient

["Ádám Szita (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-22414?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ádám Szita updated HIVE-22414:
------------------------------
    Status: Patch Available  (was: In Progress)

> Make LLAP CacheTags more memory efficient
> -----------------------------------------
>
>                 Key: HIVE-22414
>                 URL: https://issues.apache.org/jira/browse/HIVE-22414
>             Project: Hive
>          Issue Type: Improvement
>          Components: llap
>            Reporter: Ádám Szita
>            Assignee: Ádám Szita
>            Priority: Major
>         Attachments: HIVE-22414.0.patch, HIVE-22414.1.patch, HIVE-22414.2.patch, HIVE-22414.3.patch
>
>
> MultiPartitionCacheTag relies on LinkedLists.
> A LinkedList object that holds e.g. 2 nodes consumes 112 bytes roughly in this composition:
>  * 16 bytes for LinkedList object header
>  * 8 bytes for referring head
>  * 8 bytes for referring tail
>  * 80 = 2 x (16 bytes for LinkedList$Node header, 3 x 8 bytes for referring prev, next, item)
> This is a lot, so I propose to replace LinkedList in MultiPartitionCacheTag with a simple String array. (For a similar scenario an array would take 16 + 8 + 2 x 8 = 40 bytes, as per header, count, and 2 references for our actual objects).



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