19 releases (1 stable)

1.0.0 Dec 29, 2023
0.12.0 Jun 17, 2023
0.11.0 Jun 12, 2023
0.9.0 Feb 6, 2023
0.1.2 Mar 15, 2022

#532 in Parser implementations

Download history 3/week @ 2024-03-10 118/week @ 2024-03-31

68 downloads per month



ksql   Latest Version

Is a JSON data expression lexer, parser, cli and library.

How to install CLI

~ cargo install ksql


use ksql::parser::{Parser, Value};
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>>{
    let src = r#"{"name":"MyCompany", "properties":{"employees": 50}"#.as_bytes();
    let expression = ".properties.employees > 20";
    let ex = Parser::parse(expression.as_bytes())?;
    let result = ex.calculate(src)?;
    assert_eq!(Value::Bool(true), result);

CLI Usage

~ ksql '(.field1 + 1) /2' '{"field1": 1}'
echo '{"field1": 1}' | ksql '(.field1 + 1) /2'


Expressions support most mathematical and string expressions see below for details:

Syntax & Rules

Token Example Syntax Rules
Equals == supports both == and =.
Add + N/A
Subtract - N/A
Multiply * N/A
Divide / N/A
Gt > N/A
Gte >= N/A
Lt < N/A
Lte <= N/A
OpenParen ( N/A
CloseParen ) N/A
OpenBracket [ N/A
CloseBracket ] N/A
Comma , N/A
QuotedString "sample text" Must start and end with an unescaped " character
Number 123.45 Must start and end with a space or '+' or '-' when hard coded value in expression and supports 0-9 +- e characters for numbers and exponent notation.
BooleanTrue true Accepts true as a boolean only.
BooleanFalse false Accepts false as a boolean only.
SelectorPath .selector_path Starts with a . and ends with whitespace blank space. This crate currently uses gjson and so the full gjson syntax for identifiers is supported.
And && N/A
Not ! Must be before Boolean identifier or expression or be followed by an operation
Or || N/A
Contains CONTAINS Ends with whitespace blank space.
ContainsAny CONTAINS_ANY Ends with whitespace blank space.
ContainsAll CONTAINS_ALL Ends with whitespace blank space.
In IN Ends with whitespace blank space.
Between BETWEEN Starts & ends with whitespace blank space. example 1 BETWEEN 0 10
StartsWith STARTSWITH Ends with whitespace blank space.
EndsWith ENDSWITH Ends with whitespace blank space.
Coerce COERCE Coerces one data type into another using in combination with 'Identifier'. Syntax is COERCE <expression> _identifer_.
Identifier _identifier_ Starts and end with an _ used with 'COERCE' to cast data types, see table below with supported values. You can combine multiple coercions if separated by a COMMA.
Colon : N/A


Type Description
_datetime_ This attempts to convert the type into a DateTime.
_lowercase_ This converts the text into lowercase.
_uppercase_ This converts the text into uppercase.
_title_ This converts the text into title case, when the first letter is capitalized but the rest lower cased.
_string_ This converts the value into a string and supports the Value's String, Number, Bool, DateTime with nanosecond precision.
_number_ This converts the value into an f64 number and supports the Value's Null, String, Number, Bool and DateTime.
_substr_[n:n] This allows taking a substring of a string value. this returns Null if no match at specified indices exits.


Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Proteus by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


~74K SLoC