Struct QueryResults

Source

pub struct QueryResults {
    pub result: Vec<QueryResult>,
}

Expand description

Results of evaluating a Rego query.

Generates the same json representation as opa eval.

Queries typically produce a single result.

// Create engine and evaluate "1 + 1".
let results = Engine::new().eval_query("1 + 1".to_string(), false)?;

assert_eq!(results.result.len(), 1);
assert_eq!(results.result[0].expressions[0].value, Value::from(2u64));
assert_eq!(results.result[0].expressions[0].text.as_ref(), "1 + 1");

If a query contains only one expression, and even if the expression evaluates to false, the value will be returned.

// Create engine and evaluate "1 > 2" which is false.
let results = Engine::new().eval_query("1 > 2".to_string(), false)?;

assert_eq!(results.result.len(), 1);
assert_eq!(results.result[0].expressions[0].value, Value::from(false));
assert_eq!(results.result[0].expressions[0].text.as_ref(), "1 > 2");

In a query containing multiple expressions, if any expression evaluates to false, then no results are produced.

// Create engine and evaluate "true; true; false".
let results = Engine::new().eval_query("true; true; false".to_string(), false)?;

assert!(results.result.is_empty());

Note that = is different from ==. The former evaluates to undefined if the LHS and RHS are not equal. The latter evaluates to either true or false.

// Create engine and evaluate "1 = 2" which is undefined and produces no resutl.
let results = Engine::new().eval_query("1 = 2".to_string(), false)?;

assert_eq!(results.result.len(), 0);

// Create engine and evaluate "1 == 2" which evaluates to false.
let results = Engine::new().eval_query("1 == 2".to_string(), false)?;

assert_eq!(results.result.len(), 1);
assert_eq!(results.result[0].expressions[0].value, Value::from(false));
assert_eq!(results.result[0].expressions[0].text.as_ref(), "1 == 2");

Queries containing loops produce multiple results.

let results = Engine::new().eval_query("x = [1, 2, 3][_]".to_string(), false)?;

// Three results are produced, one of each value of x.
assert_eq!(results.result.len(), 3);

// Assert expressions and bindings of results.
assert_eq!(results.result[0].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[0].expressions[0].text.as_ref(), "x = [1, 2, 3][_]");
assert_eq!(results.result[0].bindings[&Value::from("x")], Value::from(1u64));

assert_eq!(results.result[1].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[1].expressions[0].text.as_ref(), "x = [1, 2, 3][_]");
assert_eq!(results.result[1].bindings[&Value::from("x")], Value::from(2u64));

assert_eq!(results.result[2].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[2].expressions[0].text.as_ref(), "x = [1, 2, 3][_]");
assert_eq!(results.result[2].bindings[&Value::from("x")], Value::from(3u64));

Loop iterations that evaluate to false or undefined don’t produce results.

let results = Engine::new().eval_query("x = [1, 2, 3][_]; x >= 2".to_string(), false)?;

// Two results are produced, one for x = 2 and another for x = 3.
assert_eq!(results.result.len(), 2);

// Assert expressions and bindings of results.
assert_eq!(results.result[0].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[0].expressions[0].text.as_ref(), "x = [1, 2, 3][_]");
assert_eq!(results.result[0].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[0].expressions[1].text.as_ref(), "x >= 2");
assert_eq!(results.result[0].bindings[&Value::from("x")], Value::from(2u64));

assert_eq!(results.result[1].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[1].expressions[0].text.as_ref(), "x = [1, 2, 3][_]");
assert_eq!(results.result[1].expressions[0].value, Value::Bool(true));
assert_eq!(results.result[1].expressions[1].text.as_ref(), "x >= 2");
assert_eq!(results.result[1].bindings[&Value::from("x")], Value::from(3u64));