encoding/json: fix and optimize marshal for quoted string #34127

breml · 2019-09-05T21:36:48Z

Since Go 1.2 every string can be marshaled to JSON without error even if it
contains invalid UTF-8 byte sequences. Therefore there is no need to use
Marshal again for the only reason of enclosing the string in double quotes.
Not using Marshal here also removes the error check as there has not been a
way for Marshal to fail anyway.

name old time/op new time/op delta
Issue34127-4 360ns ± 3% 200ns ± 3% -44.56% (p=0.008 n=5+5)

name old alloc/op new alloc/op delta
Issue34127-4 56.0B ± 0% 40.0B ± 0% -28.57% (p=0.008 n=5+5)

name old allocs/op new allocs/op delta
Issue34127-4 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.008 n=5+5)

Fixes #34154

gopherbot · 2019-09-05T21:38:46Z

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gopherbot · 2019-09-06T17:08:25Z

Message from Daniel Martí:

Patch Set 1:

Any optimization must include benchmark numbers via benchstat. For example, look at recent speed-ups in the json package. BenchmarkCodeEncoder might be a good start.

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breml · 2019-09-06T19:55:37Z

@mvdan Thanks for your hint about the benchmarks. From my point of view, the change was not primary driven by performance optimization in mind, this came more as a welcome side effect.

My motivation for the proposed change is:

remove the unnecessary error case
fix encoding/json: string option (struct tag) on string field with SetEscapeHTML(false) escapes anyway #34154

Nevertheless I will try to have a look at benchstat and provide some benchmark statistics for the improved performance as well.

gopherbot · 2019-09-06T19:57:51Z

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breml · 2019-09-06T20:14:47Z

@mvdan I had a look at the benchmarks in encoding/json and non of them contains struct fields with the string option set in the struct tags.

The change affects the encoding of struct like:

type Foo struct {
	Bar string `json:"bar,string"`
}

While looking through the commit messages for the recent changes on encoding/json I found this one from you:

...
This change should slightly reduce the amount of work when decoding into
json.Number, though that isn't very common nor part of any current
benchmarks.
...

I would argue, that this change also slightly improves encoding performance and that it is not very common nor part of any existing benchmarks. Would this be fine as well or do you insist on benchmarks for this particular case?

mvdan · 2019-09-06T20:59:00Z

Please reply on Gerrit. I'd rather not keep the discussion in two places.

gopherbot · 2019-09-09T16:37:12Z

Message from Daniel Martí:

Patch Set 2: Code-Review-1

There were some replies on GitHub - hopefully the author can post them here. Until then, -1 as per my comment above.

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gopherbot · 2019-09-09T20:03:07Z

Message from Lucas Bremgartner:

Patch Set 2:

Patch Set 1:

Any optimization must include benchmark numbers via benchstat. For example, look at recent speed-ups in the json package. BenchmarkCodeEncoder might be a good start.

Copy'n'paste from #34127 (comment)

@mvdan Thanks for your hint about the benchmarks. From my point of view, the change was not primary driven by performance optimization in mind, this came more as a welcome side effect.

My motivation for the proposed change is:

remove the unnecessary error case
fix #34154
Nevertheless I will try to have a look at benchstat and provide some benchmark statistics for the improved performance as well.

Copy'n'paste from #34127 (comment)

@mvdan I had a look at the benchmarks in encoding/json and non of them contains struct fields with the string option set in the struct tags.

The change affects the encoding of struct like:

type Foo struct {
Bar string json:"bar,string"
}
While looking through the commit messages for the recent changes on encoding/json I found this one from you:

...
This change should slightly reduce the amount of work when decoding into
json.Number, though that isn't very common nor part of any current
benchmarks.
...

I would argue, that this change also slightly improves encoding performance and that it is not very common nor part of any existing benchmarks. Would this be fine as well or do you insist on benchmarks for this particular case?

Please don’t reply on this GitHub thread. Visit golang.org/cl/193604.
After addressing review feedback, remember to publish your drafts!

gopherbot · 2019-09-09T20:13:00Z

Message from Lucas Bremgartner:

Patch Set 2:

Patch Set 2: Code-Review-1

There were some replies on GitHub - hopefully the author can post them here. Until then, -1 as per my comment above.

Please also consider the issue #34154, because it is related to this PR (in fact the issue is solved by this PR).

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gopherbot · 2019-09-09T20:16:00Z

Message from Lucas Bremgartner:

Patch Set 3: Commit message was updated.

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gopherbot · 2019-09-09T20:46:33Z

This PR (HEAD: b4da9fd) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/go/+/193604 to see it.

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gopherbot · 2019-09-09T21:01:47Z

This PR (HEAD: 96aea0f) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/go/+/193604 to see it.

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gopherbot · 2019-09-09T21:34:04Z

Message from Daniel Martí:

Patch Set 8:

(5 comments)

Thanks, I didn't know there was an issue to fix here. My previous CL didn't include benchmark numbers because it wasn't a performance optimization. I was simply deleting dead code, so I imagined that the edge case would be a bit faster.

If this CL is about making JSON encoding follow an option correctly, and that's the bug you filed, then no need to add the benchmark. I only insisted on that because the original CL was written in a way that seemed like you were optimizing the code :)

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Since Go 1.2 every string can be marshaled to JSON without error even if it contains invalid UTF-8 byte sequences. Therefore there is no need to use Marshal again for the only reason of enclosing the string in double quotes. Not using Marshal here also removes the error check as there has not been a way for Marshal to fail anyway. name old time/op new time/op delta Issue34127-4 360ns ± 3% 200ns ± 3% -44.56% (p=0.008 n=5+5) name old alloc/op new alloc/op delta Issue34127-4 56.0B ± 0% 40.0B ± 0% -28.57% (p=0.008 n=5+5) name old allocs/op new allocs/op delta Issue34127-4 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.008 n=5+5) Fixes golang#34154

gopherbot · 2019-09-10T18:52:08Z

This PR (HEAD: 9b0ac1d) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/go/+/193604 to see it.

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gopherbot · 2019-09-10T18:56:12Z

Message from Lucas Bremgartner:

Patch Set 10:

(5 comments)

I have updated the commit message and integrated the test into an existing table driven test.

I have also added the ideas, I considered regarding the implementation without make+append.

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andig · 2019-09-10T19:06:59Z

For some reason I cannot comment on the CL. I have a stupid suggestion that might be worth trying. In https://go-review.googlesource.com/c/go/+/194338 an encodeBuffer from Pool is used to optimize allocations. Being in the same package it might also lend itself here instead of the bytes array. However, it contains overhead and cannot be allocated to the desired size. May not be worth it in the end or not even the cleanest thing to do.

gopherbot · 2019-09-11T05:40:39Z

Message from Andreas Goetz:

Patch Set 10:

Patch Set 10:

(5 comments)

I have updated the commit message and integrated the test into an existing table driven test.

I have also added the ideas, I considered regarding the implementation without make+append.

Couldn't 607 just be like this:

	e.WriteByte('"')
	e.string(v.String(), opts.escapeHTML)
	e.WriteByte('"')

without the additional []byte allocation?

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gopherbot · 2019-09-11T05:54:25Z

Message from Lucas Bremgartner:

Patch Set 10:

Patch Set 10:

Patch Set 10:

(5 comments)

I have updated the commit message and integrated the test into an existing table driven test.

I have also added the ideas, I considered regarding the implementation without make+append.

Couldn't 607 just be like this:
  e.WriteByte('"')
  e.string(v.String(), opts.escapeHTML)
  e.WriteByte('"')
without the additional []byte allocation?

This was my very first try as well, when I approached the problem. Unfortunately, this does not work, because e.string adds the double quotes as well (see:

go/src/encoding/json/encode.go

Line 954 in cf63058

e.WriteByte('"')

). So you end up with invalid json like this, because the inner quotes are not escaped properly:

 { "foo": ""bar"" }

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gopherbot · 2019-09-11T06:08:39Z

Message from Andreas Goetz:

Patch Set 10:

Patch Set 10:
Couldn't 607 just be like this:
	e.WriteByte('"')
	e.string(v.String(), opts.escapeHTML)
	e.WriteByte('"')
without the additional []byte allocation?
This was my very first try as well, when I approached the problem. Unfortunately, this does not work, because e.string adds the double quotes as well (see:

go/src/encoding/json/encode.go

Line 954 in cf63058

e.WriteByte('"')

). So you end up with invalid json like this, because the inner quotes are not escaped properly:
 { "foo": ""bar"" }

Ok, please tell me off if I'm confusing the discussion. Isn't then your patch really equal to:

e.string(v.String(), opts.escapeHTML)

and basically means that the entire optQuoted block could really be removed?

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gopherbot · 2019-09-11T06:49:52Z

Message from Lucas Bremgartner:

Patch Set 10:

Patch Set 10:
Patch Set 10:
Couldn't 607 just be like this:
  e.WriteByte('"')
  e.string(v.String(), opts.escapeHTML)
  e.WriteByte('"')
without the additional []byte allocation?
This was my very first try as well, when I approached the problem. Unfortunately, this does not work, because e.string adds the double quotes as well (see:

go/src/encoding/json/encode.go

Line 954 in cf63058

e.WriteByte('"')

). So you end up with invalid json like this, because the inner quotes are not escaped properly:
 { "foo": ""bar"" }
Ok, please tell me off if I'm confusing the discussion. Isn't then your patch really equal to:
e.string(v.String(), opts.escapeHTML)
and basically means that the entire optQuoted block could really be removed?

No, the optQuoted flag is controlled by the "string" option in the json struct tags. The docs (https://golang.org/pkg/encoding/json/#Marshal) says:

The "string" option signals that a field is stored as JSON inside a JSON-encoded string. It applies only to fields of string, floating point, integer, or boolean types.

This means, that any string, that is encoded, is put into additional (escaped) quotes. E.g.

{ "foo": "\"bar\"" }

I suggest, you consult the added test case (https://go-review.googlesource.com/c/go/+/193604/10/src/encoding/json/stream_test.go) to see the expected output from a given input.

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gopherbot · 2019-09-11T12:13:40Z

Message from Daniel Martí:

Patch Set 10: Run-TryBot+1 Code-Review+2

Thanks for the throrough explanation, Lucas! LGTM.

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gopherbot · 2019-09-11T12:14:43Z

Message from Gobot Gobot:

Patch Set 10:

TryBots beginning. Status page: https://farmer.golang.org/try?commit=ed63614a

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gopherbot · 2019-09-11T12:24:32Z

Message from Gobot Gobot:

Patch Set 10: TryBot-Result+1

TryBots are happy.

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Since Go 1.2 every string can be marshaled to JSON without error even if it contains invalid UTF-8 byte sequences. Therefore there is no need to use Marshal again for the only reason of enclosing the string in double quotes. Not using Marshal here also removes the error check as there has not been a way for Marshal to fail anyway. name old time/op new time/op delta Issue34127-4 360ns ± 3% 200ns ± 3% -44.56% (p=0.008 n=5+5) name old alloc/op new alloc/op delta Issue34127-4 56.0B ± 0% 40.0B ± 0% -28.57% (p=0.008 n=5+5) name old allocs/op new allocs/op delta Issue34127-4 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.008 n=5+5) Fixes #34154 Change-Id: Ib60dc11980f9b20d8bef2982de7168943d632263 GitHub-Last-Rev: 9b0ac1d GitHub-Pull-Request: #34127 Reviewed-on: https://go-review.googlesource.com/c/go/+/193604 Reviewed-by: Daniel Martí <[email protected]> Run-TryBot: Daniel Martí <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>

gopherbot · 2019-09-11T12:28:48Z

This PR is being closed because golang.org/cl/193604 has been merged.

Since Go 1.2 every string can be marshaled to JSON without error even if it contains invalid UTF-8 byte sequences. Therefore there is no need to use Marshal again for the only reason of enclosing the string in double quotes. Not using Marshal here also removes the error check as there has not been a way for Marshal to fail anyway. name old time/op new time/op delta Issue34127-4 360ns ± 3% 200ns ± 3% -44.56% (p=0.008 n=5+5) name old alloc/op new alloc/op delta Issue34127-4 56.0B ± 0% 40.0B ± 0% -28.57% (p=0.008 n=5+5) name old allocs/op new allocs/op delta Issue34127-4 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.008 n=5+5) Fixes #34154 Change-Id: Ib60dc11980f9b20d8bef2982de7168943d632263 GitHub-Last-Rev: 9b0ac1d4c5318b6bf9ed7930320f2bd755f9939c GitHub-Pull-Request: golang/go#34127 Reviewed-on: https://go-review.googlesource.com/c/go/+/193604 Reviewed-by: Daniel Martí <[email protected]> Run-TryBot: Daniel Martí <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>

googlebot added the cla: yes Used by googlebot to label PRs as having a valid CLA. The text of this label should not change. label Sep 5, 2019

breml mentioned this pull request Sep 6, 2019

encoding/json: string option (struct tag) on string field with SetEscapeHTML(false) escapes anyway #34154

Closed

breml force-pushed the optimize-json-quoted-string branch from d4bf400 to d417e71 Compare September 6, 2019 19:57

breml force-pushed the optimize-json-quoted-string branch from d417e71 to b4da9fd Compare September 9, 2019 20:45

breml force-pushed the optimize-json-quoted-string branch from b4da9fd to 96aea0f Compare September 9, 2019 21:01

breml changed the title ~~encoding/json: optimize marshal for quoted string~~ encoding/json: fix and optimize marshal for quoted string Sep 10, 2019

breml force-pushed the optimize-json-quoted-string branch from 96aea0f to 9b0ac1d Compare September 10, 2019 18:51

gopherbot closed this Sep 11, 2019

gabyhelp mentioned this pull request Jun 26, 2024

proposal: encoding/json: avoid massive escape costs #68203

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encoding/json: fix and optimize marshal for quoted string #34127

encoding/json: fix and optimize marshal for quoted string #34127

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encoding/json: fix and optimize marshal for quoted string #34127

encoding/json: fix and optimize marshal for quoted string #34127

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