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https://issues.apache.org/jira/browse/HIVE-14318?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gopal V updated HIVE-14318:
---------------------------
Status: Patch Available (was: Open)
> Vectorization: LIKE should use matches() instead of find(0)
> -----------------------------------------------------------
>
> Key: HIVE-14318
> URL: https://issues.apache.org/jira/browse/HIVE-14318
> Project: Hive
> Issue Type: Bug
> Components: Vectorization
> Affects Versions: 1.2.1, 1.3.0, 2.2.0
> Reporter: Gopal V
> Assignee: Gopal V
> Attachments: HIVE-14318.1.patch
>
>
> Checking for a match instead of find() would allow matcher to exit early
> instead of looking for sub-sequences beyond the first non-match.
> In UDFLike.java, the complex pattern checker uses matches() and the
> vectorized version uses find(0), which is more expensive.
> {code}
> Benchmark Mode Cnt Score Error Units
> RegexBench.testGreedyRegexHit avgt 5 379.316 ± 32.444 ns/op
> RegexBench.testGreedyRegexHitCheck avgt 5 344.895 ± 15.436 ns/op
> RegexBench.testGreedyRegexMiss avgt 5 497.193 ± 18.168 ns/op
> RegexBench.testGreedyRegexMissCheck avgt 5 171.872 ± 8.588 ns/op
> {code}
> The miss in match is nearly ~3x more expensive per-row with the .find(0) over
> the .match() check version.
> The pattern match scenario is nearly the same.
> The lazy scenario makes it slower when there's a hit (because match runs the
> check till end, but ~2x faster when there's a miss).
> {code}
> RegexBench.testLazyRegexHit avgt 5 78.398 ± 6.007 ns/op
> RegexBench.testLazyRegexHitCheck avgt 5 120.557 ± 4.396 ns/op
> RegexBench.testLazyRegexMiss avgt 5 387.594 ± 25.672 ns/op
> RegexBench.testLazyRegexMissCheck avgt 5 154.489 ± 13.622 ns/op
> {code}
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