mirror of https://github.com/minio/minio.git
94 lines
2.5 KiB
Markdown
94 lines
2.5 KiB
Markdown
|
<p align="center"><img width="350px" src="jstream.png" alt="jstream"/></p>
|
||
|
|
|
||
|
|
#
|
||
|
|
|
||
|
|
[](https://godoc.org/github.com/bcicen/jstream)
|
||
|
|
|
||
|
|
|
||
|
|
`jstream` is a streaming JSON parser and value extraction library for Go.
|
||
|
|
|
||
|
|
Unlike most JSON parsers, `jstream` is document position- and depth-aware -- this enables the extraction of values at a specified depth, eliminating the overhead of allocating encompassing arrays or objects; e.g:
|
||
|
|
|
||
|
|
Using the below example document:
|
||
|
|
<img width="85%" src="https://bradley.codes/static/img/jstream-levels.gif" alt="jstream"/>
|
||
|
|
|
||
|
|
we can choose to extract and act only the objects within the top-level array:
|
||
|
|
```go
|
||
|
|
f, _ := os.Open("input.json")
|
||
|
|
decoder := jstream.NewDecoder(f, 1) // extract JSON values at a depth level of 1
|
||
|
|
for mv := range decoder.Stream() {
|
||
|
|
fmt.Printf("%v\n ", mv.Value)
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
output:
|
||
|
|
```
|
||
|
|
map[desc:RGB colors:[red green blue]]
|
||
|
|
map[desc:CMYK colors:[cyan magenta yellow black]]
|
||
|
|
```
|
||
|
|
|
||
|
|
likewise, increasing depth level to `3` yields:
|
||
|
|
```
|
||
|
|
red
|
||
|
|
green
|
||
|
|
blue
|
||
|
|
cyan
|
||
|
|
magenta
|
||
|
|
yellow
|
||
|
|
black
|
||
|
|
```
|
||
|
|
|
||
|
|
optionally, kev:value pairs can be emitted as an individual struct:
|
||
|
|
```go
|
||
|
|
decoder := jstream.NewDecoder(f, 2).EmitKV() // enable KV streaming at a depth level of 2
|
||
|
|
```
|
||
|
|
|
||
|
|
```
|
||
|
|
jstream.KV{desc RGB}
|
||
|
|
jstream.KV{colors [red green blue]}
|
||
|
|
jstream.KV{desc CMYK}
|
||
|
|
jstream.KV{colors [cyan magenta yellow black]}
|
||
|
|
```
|
||
|
|
|
||
|
|
## Installing
|
||
|
|
|
||
|
|
```bash
|
||
|
|
go get github.com/bcicen/jstream
|
||
|
|
```
|
||
|
|
|
||
|
|
## Commandline
|
||
|
|
|
||
|
|
`jstream` comes with a cli tool for quick viewing of parsed values from JSON input:
|
||
|
|
|
||
|
|
```bash
|
||
|
|
cat input.json | jstream -v -d 1
|
||
|
|
depth start end type | value
|
||
|
|
|
||
|
|
1 004 069 object | {"colors":["red","green","blue"],"desc":"RGB"}
|
||
|
|
1 073 153 object | {"colors":["cyan","magenta","yellow","black"],"desc":"CMYK"}
|
||
|
|
```
|
||
|
|
|
||
|
|
### Options
|
||
|
|
|
||
|
|
Opt | Description
|
||
|
|
--- | ---
|
||
|
|
-d \<n\> | emit values at depth n. if n < 0, all values will be emitted
|
||
|
|
-v | output depth and offset details for each value
|
||
|
|
-h | display help dialog
|
||
|
|
|
||
|
|
## Benchmarks
|
||
|
|
|
||
|
|
Obligatory benchmarks performed on files with arrays of objects, where the decoded objects are to be extracted.
|
||
|
|
|
||
|
|
Two file sizes are used -- regular (1.6mb, 1000 objects) and large (128mb, 100000 objects)
|
||
|
|
|
||
|
|
input size | lib | MB/s | Allocated
|
||
|
|
--- | --- | --- | ---
|
||
|
|
regular | standard | 97 | 3.6MB
|
||
|
|
regular | jstream | 175 | 2.1MB
|
||
|
|
large | standard | 92 | 305MB
|
||
|
|
large | jstream | 404 | 69MB
|
||
|
|
|
||
|
|
In a real world scenario, including initialization and reader overhead from varying blob sizes, performance can be expected as below:
|
||
|
|
<img src="https://bradley.codes/static/img/bench.svg" alt="jstream"/>
|