[HIVE-13196] UDFLike: reduce Regex NFA sizes

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.2.1, 1.3.0, 2.0.0, 2.1.0
• Fix Version/s: 2.1.0
• Component/s: UDF
• Target Version/s: 2.1.0
• Assignee: Gopal Vijayaraghavan
• Reporter: Gopal Vijayaraghavan
• Created: 02/Mar/16 06:40
• Updated: 27/Jul/16 05:15
• Resolved: 31/May/16 18:08

Description

The NFAs built from complex regexes in UDFLike are extremely complex and spend a lot of time doing simple expression matching with no backtracking.

Prevent NFA -> DFA explosion by using reluctant regex matches instead of greedy matches.

Issue Links

• is required by: HIVE-14349 Vectorization: LIKE should anchor the regexes