[GROOVY-9637] Improve the performance of GString

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Assignee: Paul King
• Reporter: Daniel Sun
• Created: 12/Jul/20 16:12
• Updated: 11/Nov/20 02:00
• Resolved: 31/Jul/20 22:53

Description

GString will run toString() whenever its literal string is needed, e.g. methods like equals, hashCode are called, but unfortunately its literal string will be re-constructed for each time and the process costs quite a little of time.

So I propose to check whether GString values are all of immutable type, e.g. primitive types and their boxed type, String, etc. If yes, use the cached string literal, otherwise re-construct the literal string.

Here is the test script, Groovy 3.0.5 costs about 8700ms, and PR1329 costs about 290ms on my machine. About 96.7% time is reduced.

def gstr = makeGString()
long b = System.currentTimeMillis()
for (int i = 0; i < 10000000; i++) {
	gstr.toString()
}
long e = System.currentTimeMillis()
println "${e - b}ms"

//@groovy.transform.CompileStatic
def makeGString() {
    def now = java.time.LocalDateTime.now()
    "integer: ${1}, double: ${1.2d}, string: ${'x'}, class: ${Map.class}, boolean: ${true}, now: ${now}"
}