Performance Degradation Starting In v5.2.0

[SyntaxNode]

Greetings From https://github.com/prebid/prebid-server

We use json-patch in our project and observed a performance difference when we upgraded to v5 from an older version. This is a high scale application which is particularly sensitive to memory allocations. I turned the MergePatch example in the readme to a benchmark test and found the following results on the 5.2.0 and 5.1.0 version branches with Go 1.16:

func BenchmarkMergePatch(b *testing.B) {
	original := []byte(`{"name": "John", "age": 24, "height": 3.21}`)
	target := []byte(`{"name": "Jane", "age": 24}`)
	alternative := []byte(`{"name": "Tina", "age": 28, "height": 3.75}`)

	patch, err := CreateMergePatch(original, target)
	if err != nil {
		panic(err)
	}

	for n := 0; n < b.N; n++ {
		MergePatch(alternative, patch)
	}
}

v5.2.0  BenchmarkMergePatch-12    	   85310	     14823 ns/op	    6454 B/op	     154 allocs/op
v5.1.0  BenchmarkMergePatch-12    	  216194	      6405 ns/op	    2634 B/op	      56 allocs/op

v5.2.0+ is using significantly more memory in terms of bytes and allocations. I am curious if this is a known change or perhaps we need to modify our calls to optimize for lower memory usage?

Thank you.

[evanphx]

Sorry for the long delay, I'm looking into this. Part of the reason is some correctness fixes.

[SyntaxNode]

No worries. Thank you for the fix.