Gopal V created HIVE-14318:
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Summary: 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
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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