[jira] [Resolved] (IMPALA-5559) Frontend and backend have different notions of which slots are var-len.

["Tim Armstrong (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-5559?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong resolved IMPALA-5559.
-----------------------------------
       Resolution: Won't Fix
    Fix Version/s: Impala 2.10.0

The fix for IMPALA-5560 removed the only case where these were different in practice. There's still some ambiguity here but it's not practically important at the moment.

> Frontend and backend have different notions of which slots are var-len.
> -----------------------------------------------------------------------
>
>                 Key: IMPALA-5559
>                 URL: https://issues.apache.org/jira/browse/IMPALA-5559
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Frontend
>    Affects Versions: Impala 2.10.0
>            Reporter: Tim Armstrong
>            Assignee: Tim Armstrong
>              Labels: resource-management
>             Fix For: Impala 2.10.0
>
>
> I discovered this on my buffer pool dev branch because the planner miscomputed the amount of reservation required for the sorter on this query:
> {code}
> select t1.cl, COUNT(1) FROM chars_tiny t1 GROUP BY 1 ORDER BY t1.cl
> {code}
> The frontend thinks that it doesn't need var-len data blocks to store t1.cl, which is a large CHAR() column.
> I think the problem is that two different concepts are being confused in the code:
> * Is the amount of storage required for the slot always a fixed amount?
> * Does the slot store data out-of-line from the main tuple?



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