Introduce Date._strptime in Java to improve the performance

[muga]

Overview

• I want to improve the performance of Date._strptime method.
• I'm implementing Date._strptime in Java on Java timestamp parser and RubyDateParser embulk/embulk#608
• Can you consider about introducing our implementation to JRuby? If you agree, I will work on it after completing the implementation.

Details

My application, Embulk, is using JRuby and heavily using Date._strptime method internally to parse timestamp strings. I found that the heavy usage is one of the performance bottlenecks in my application.
To mitigate the performance issue, I started implementing Date._strptime in Java. The features are:

• 100% compatibility with the specification of Date._strptime in CRuby
• Faster performance because the # of objects passing is reduced between Java and (J)Ruby
• The implementation uses similar approach with org.jruby.util.RubyDateFormatter and org.jruby.lexer.StrftimeLexer.

Environment

• JRuby 9.1.5.0
• Java 1.8.0_91 64-Bit Server VM (build 25.91-b14, mixed mode)
• Ubuntu 16.04

[headius]

@muga We'd love to incorporate your implementation! Provide a PR and let us know you consent to it being in JRuby under our tri-license (GPL 2, LGPL 2, EPL). Thank you!

[muga]

@headius Thank you for letting me know. I complete the implementation and then create new PR.

[kares]

related #3640 (includes some numbers) ... @muga JRuby 9.2 would be perfect timing for delivery :)

[muga]

@kares We started reviewing the implementation on our application github repo embulk/embulk#611. I'll do my best :)

[muga]

I'm closing this ticket because #4635 was merged into master.