11 releases
new 0.4.4 | Nov 16, 2024 |
---|---|
0.4.1 | Jul 18, 2024 |
0.3.0 | Oct 13, 2023 |
0.2.3 | Jul 10, 2023 |
0.1.1 | Mar 3, 2023 |
#292 in Encoding
3,291 downloads per month
Used in 6 crates
(3 directly)
740KB
6K
SLoC
jsonb
jsonb
is a binary format JSON
representation inspired by PostgreSQL and CockroachDB. It provides a fast, lightweight and easy-to-use API for working with JSON
data.
Features
- Good compatibility:
jsonb
fully supports theJSON
standard and can be used to store complex data structures. - Fast performance:
jsonb
is designed for high performance, allowing you to work with largeJSON
data sets with ease. - Easy to use:
jsonb
provides a number of built-in functions to support various operations, and also supports theJSONPath
syntax for selecting and extracting subset elements. - Safe and secure:
jsonb
is written in Rust, which provides memory and thread safety guarantees, making it a safe choice for handling sensitive data.
Encoding format
The jsonb
encoding format is a tree-like structure. Each node contains a container header, a number of JEntry headers, and nested encoding values.
- 32-bit container header. 3 bits identify the type of value, including
scalar
,object
andarray
, and 29 bits identify the number of JEntries in thearray
orobject
. The root node of thejsonb
value is always a container header.scalar
container header:0x20000000
object
container header:0x40000000
array
container header:0x80000000
- 32-bit JEntry header. 1 bit identifies whether the JEntry stores a length or an offset, 3 bits identify the type of value, including
null
,string
,number
,false
,true
andcontainer
, and the remaining 28 bits identify the length or offset of the encoding value.null
JEntry header:0x00000000
string
JEntry header:0x10000000
number
JEntry header:0x20000000
false
JEntry header:0x30000000
true
JEntry header:0x40000000
container
JEntry header0x50000000
- Encoding value. Different types of JEntry header have different encoding values.
null
,true
,false
: no encoding value, identified by the JEntry header.string
: a normal UTF-8 string.number
: an encoded number to represent uint64s, int64s and float64s.container
: a nestedjson
value with a recursive structure.
An encoding example
// JSON value
[false, 10, {"k":"v"}]
// JSONB encoding
0x80000003 array container header (3 JEntries)
0x30000000 false JEntry header (no encoding value)
0x20000002 number JEntry header (encoding value length 2)
0x5000000e container JEntry header (encoding value length 14)
0x500a number encoding value (10)
0x40000001 object container header (1 JEntry)
0x10000001 string key JEntry header (encoding value length 1)
0x10000001 string value JEntry header (encoding value length 1)
0x6b string encoding value ("k")
0x76 string encoding value ("v")
Jsonb value
The jsonb
value is an enumeration that represents all kinds of JSON
values and serves as an intermediate for converting other data types to the jsonb
binary format value.
// jsonb value
#[derive(Clone, PartialEq, Eq)]
pub enum Value<'a> {
Null,
Bool(bool),
String(Cow<'a, str>),
Number(Number),
Array(Vec<Value<'a>>),
Object(Object<'a>),
}
Built-in functions
jsonb
implements a number of commonly used built-in functions. Since most functions only focus on a subset of the total value, using container headers and JEntry headers to can efficiently skip over intermediate parts of the jsonb
value. This avoids time-consuming deserialisation operations and provides very high performance. For more information, see https://docs.rs/jsonb/latest/jsonb/#functions
SQL/JSONPath
SQL/JSONPath is a query language used to select and extract a subset of elements from a jsonb
value.
Operators
The following operators have been implemented:
Operator | Description | Examples |
---|---|---|
$ |
The root element | $ |
@ |
The current element in the filter expression | $.event?(@ == 1) |
.* |
Selecting all elements in an Object | $.* |
.<name> |
Selecting element that match the name in an Object | $.event |
:<name> |
Alias of .<name> |
$:event |
["<name>"] |
Alias of .<name> |
$["event"] |
[*] |
Selecting all elements in an Array | $[*] |
[<pos>, ..] |
Selecting 0-based n-th elements in an Array |
$[1, 2] |
[last - <pos>, ..] |
Selecting n-th element before the last element in an Array |
$[0, last - 1] |
[<pos1> to <pos2>, ..] |
Selecting all elements of a range in an Array | $[1 to last - 2] |
?(<expr>) |
Selecting all elements that matched the filter expression | $?(@.price < 10) |
Examples
fn main() {
let json = r#"
{
"name":"Fred",
"phones":[
{
"type":"home",
"number":3720453
},
{
"type": "work",
"number":5062051
}
]
}"#;
let path = r#"$.phones[*]?(@.number == 3720453)"#;
// parse JSON string to jsonb value
let value = jsonb::parse_value(json.as_bytes()).unwrap();
// encode jsonb value to jsonb binary value
let jsonb = value.to_vec();
// parse JSONPath string
let json_path = jsonb::jsonpath::parse_json_path(path.as_bytes()).unwrap();
// select subset value from jsonb binary value
let mut sub_jsonb = Vec::new();
let mut sub_offsets = Vec::new();
jsonb::get_by_path(&jsonb, json_path, &mut sub_jsonb, &mut sub_offsets);
// value={"number":3720453,"type":"home"}
println!("value={}", jsonb::to_string(&sub_jsonb));
}
Contributing
jsonb
is an open source project and all kinds of contributions are welcome! You can help with ideas, code or documentation.
License
Licensed under the Apache License, Version 2.0
Dependencies
~2.5–3.5MB
~63K SLoC