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encoding/json: json.Decoder Token method is two times slow than Decode #58786

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bigpigeon opened this issue Feb 28, 2023 · 3 comments
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encoding/json: json.Decoder Token method is two times slow than Decode #58786

bigpigeon opened this issue Feb 28, 2023 · 3 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Performance
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@bigpigeon
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question

I need Depth limit decode function with json data

but std json did not support, I want to use json.Decoder.Token to implement it

performance test

I write below benchmark to test it's performance

https://gist.github.com/bigpigeon/93f90fe84cf96f10356541c22db6e7dc

# go test -test.bench ".*" decode_test.go 
goos: linux
goarch: amd64
cpu: Intel(R) Core(TM) i5-8500 CPU @ 3.00GHz
BenchmarkJsonDecode-6   	  331059	      4878 ns/op	    3984 B/op	      44 allocs/op
BenchmarkGetToken-6     	  146536	      7969 ns/op	    3064 B/op	     135 allocs/op
PASS
ok  	command-line-arguments	2.907s

the getAllToken is even slower than Decode

What version of Go are you using (go version)?

$ go version
go version go1.19.1 linux/amd64
@dmitshur dmitshur added Performance NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Feb 28, 2023
@dmitshur dmitshur added this to the Backlog milestone Feb 28, 2023
@dmitshur
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CC @dsnet, @bradfitz, @mvdan.

@dsnet
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dsnet commented Feb 28, 2023

Closing as a duplicate of #40128. A huge part of it's slowness is the fact that it allocates.

@dsnet dsnet closed this as completed Feb 28, 2023
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dsnet commented Feb 28, 2023

On a different note, if you want to a propose a Decoder.SetDepthLimit method, that can filed separately and can be considered.

@dsnet dsnet mentioned this issue Mar 3, 2023
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