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Posted to issues@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2018/01/18 21:48:00 UTC

[jira] [Commented] (HIVE-18487) Vectorization: Undecoded utf-8 fast-path for _ wildcards in LIKE

    [ https://issues.apache.org/jira/browse/HIVE-18487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16331283#comment-16331283 ] 

Gopal V commented on HIVE-18487:
--------------------------------

Specific corner-case is that the _ wildcard can represent anywhere between 1-6 bytes in UTF-8.

> Vectorization: Undecoded utf-8 fast-path for _ wildcards in LIKE
> ----------------------------------------------------------------
>
>                 Key: HIVE-18487
>                 URL: https://issues.apache.org/jira/browse/HIVE-18487
>             Project: Hive
>          Issue Type: Improvement
>    Affects Versions: 3.0.0
>            Reporter: Gopal V
>            Priority: Major
>
> Queries with "%" are optimized using the BoyerMooreHorspool lookups, while the simpler single char wildcard "_" isn't optimized to be faster.
> [https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/AbstractFilterStringColLikeStringScalar.java]
> Has Begin, End, Middle and Chained checkers for "%", but no option to handle "_" in the chained mode.



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