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https://issues.apache.org/jira/browse/HIVE-26047?focusedWorklogId=746464&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-746464
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ASF GitHub Bot logged work on HIVE-26047:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 23/Mar/22 10:09
Start Date: 23/Mar/22 10:09
Worklog Time Spent: 10m
Work Description: zabetak commented on pull request #3117:
URL: https://github.com/apache/hive/pull/3117#issuecomment-1076183992
If I understand well the problem may appear when a certain `LIKE` pattern is
relatively big. Most, if not all, of the supported patterns can be identified
with a linear complexity algorithm. Identifying the type of pattern using
regular expressions (`java.util.regex.Pattern` or `com.google.re2j.Pattern`),
although convenient, can hardly become more efficient than a custom algorithm.
If we want to avoid the performance hit of JDK-8203458 for the specific case of
`LIKE` patterns then going for custom implementation should be the way to go.
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Issue Time Tracking
-------------------
Worklog Id: (was: 746464)
Time Spent: 0.5h (was: 20m)
> Vectorized LIKE UDF should use Re2J regex to address JDK-8203458
> ----------------------------------------------------------------
>
> Key: HIVE-26047
> URL: https://issues.apache.org/jira/browse/HIVE-26047
> Project: Hive
> Issue Type: Bug
> Reporter: Naresh P R
> Assignee: Naresh P R
> Priority: Major
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Below pattern is taking a long time to validate regex in java8 with same
> trace as shown in java bug
> [JDK-8203458|https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8203458]
>
> {code:java}
> import java.util.regex.Pattern;
> public class Test {
> public static void main(String args[]) {
> String pattern =
> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_b";
>
> Pattern CHAIN_PATTERN = Pattern.compile("(%?[^%_\\\\]+%?)+");
> CHAIN_PATTERN.matcher(pattern).matches();
> }
> }
> {code}
> Same is reproducible with following SQL
> {code:java}
> create table table1(name string);
> insert into table1 (name) values
> ('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_b');
> select * from table1 where name like
> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_b";{code}
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