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Posted to issues-all@impala.apache.org by "Tim Armstrong (Jira)" <ji...@apache.org> on 2020/06/26 01:11:00 UTC
[jira] [Resolved] (IMPALA-7020) Order by expressions in Analytical
functions are not materialized causing slowdown
[ https://issues.apache.org/jira/browse/IMPALA-7020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Tim Armstrong resolved IMPALA-7020.
-----------------------------------
Fix Version/s: Impala 4.0
Resolution: Fixed
> Order by expressions in Analytical functions are not materialized causing slowdown
> ----------------------------------------------------------------------------------
>
> Key: IMPALA-7020
> URL: https://issues.apache.org/jira/browse/IMPALA-7020
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Affects Versions: Impala 2.12.0
> Reporter: Mostafa Mokhtar
> Assignee: Tim Armstrong
> Priority: Major
> Labels: performance
> Fix For: Impala 4.0
>
> Attachments: Slow case profile.txt, Workaround profile.txt
>
>
> Order by expressions in Analytical functions are not materialized and cause queries to run much slower.
> The rewrite for the query below is 20x faster, profiles attached.
> Repro
> {code}
> select *
> FROM
> (
> SELECT
> o.*,
> ROW_NUMBER() OVER(ORDER BY evt_ts DESC) AS rn
> FROM
> (
> SELECT
> l_orderkey,l_partkey,l_linenumber,l_quantity, cast (l_shipdate as string) evt_ts
> FROM
> lineitem
> WHERE
> l_shipdate BETWEEN '1992-01-01 00:00:00' AND '1992-01-15 00:00:00'
> ) o
> ) r
> WHERE
> rn BETWEEN 1 AND 101
> ORDER BY rn;
> {code}
> Workaround
> {code}
> select *
> FROM
> (
> SELECT
> o.*,
> ROW_NUMBER() OVER(ORDER BY evt_ts DESC) AS rn
> FROM
> (
> SELECT
> l_orderkey,l_partkey,l_linenumber,l_quantity, cast (l_shipdate as string) evt_ts
> FROM
> lineitem
> WHERE
> l_shipdate BETWEEN '1992-01-01 00:00:00' AND '1992-01-15 00:00:00'
> union all
> SELECT
> l_orderkey,l_partkey,l_linenumber,l_quantity, cast (l_shipdate as string) evt_ts
> FROM
> lineitem limit 0
>
> ) o
> ) r
> WHERE
> rn BETWEEN 1 AND 101
> ORDER BY rn;
> {code}
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