[HIVE-14318] Vectorization: LIKE should use matches() instead of find(0)

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 1.2.1, 1.3.0, 2.2.0
• Component/s: Vectorization
• Target Version/s: 1.3.0, 2.2.0
• Assignee: Gopal Vijayaraghavan
• Reporter: Gopal Vijayaraghavan
• Created: 23/Jul/16 01:01
• Updated: 27/Jul/16 00:10
• Resolved: 26/Jul/16 02:21

Description

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.

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

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).

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

Issue Links

• relates to: HIVE-14349 Vectorization: LIKE should anchor the regexes