Struct Query 

pub struct Query { /* private fields */ }

A SPARQL query configured before execution (ADR-009).

Examples

ASK:

use oxiland::terms::{self, Literal, Triple};
use oxiland::{Model, Query, QueryResults};

let model = Model::new()?;
model.add(Triple::new(
    terms::named_node("https://example.com/alice")?,
    terms::named_node("https://example.com/name")?,
    Literal::new_simple_literal("Alice"),
))?;

let results = Query::new("ASK { ?s ?p ?o }").execute(&model)?;
assert!(matches!(results, QueryResults::Boolean(true)));

SELECT with limit:

use oxiland::terms::{self, Literal, Triple};
use oxiland::{Model, Query, QueryResults};

let model = Model::new()?;
model.add(Triple::new(
    terms::named_node("https://example.com/alice")?,
    terms::named_node("https://example.com/name")?,
    Literal::new_simple_literal("Alice"),
))?;

let results = Query::new(
    "SELECT ?name WHERE { <https://example.com/alice> <https://example.com/name> ?name }",
)
.limit(1)?
.execute(&model)?;

if let QueryResults::Solutions(mut solutions) = results {
    let solution = solutions
        .next()
        .expect("one row")
        .map_err(|error| oxiland::Error::SparqlEvaluation(error.to_string()))?;
    assert!(solution.get("name").is_some());
}

Implementations

impl Query

pub fn new(text: impl Into<String>) -> Self

Creates a SPARQL query from its text.

pub fn as_str(&self) -> &str

Returns the query text.

pub fn base_iri(self, base_iri: impl Into<String>) -> Result<Self>

Sets the base IRI used while parsing the query.

Invalid IRIs return Error::InvalidRdf.

pub fn prefix( self, prefix_name: impl Into<String>, prefix_iri: impl Into<String>, ) -> Result<Self>

Adds a default IRI prefix used while parsing the query.

Invalid IRIs return Error::InvalidRdf.

pub fn limit(self, limit: usize) -> Result<Self>

Sets an API-level result limit (algebra Slice; ADR-009).

Replaces any in-query LIMIT/OFFSET slice on SELECT/CONSTRUCT/DESCRIBE. ASK queries return Error::Unsupported here (not only at execute).

pub fn offset(self, offset: usize) -> Result<Self>

Sets an API-level result offset (algebra Slice; ADR-009).

Replaces any in-query LIMIT/OFFSET slice on SELECT/CONSTRUCT/DESCRIBE. ASK queries return Error::Unsupported here (not only at execute).

pub fn default_graph(self, graphs: impl IntoIterator<Item = GraphName>) -> Self

Restricts the query default graph to the given graph names.

An empty list selects an empty default dataset (no triples match from the default graph).

pub fn default_graph_as_union(self) -> Self

Treats the union of all named graphs as the default graph.

pub fn available_named_graphs( self, graphs: impl IntoIterator<Item = NamedOrBlankNode>, ) -> Self

Restricts available named graphs for the query dataset.

pub fn cancellation_token(self, token: CancellationToken) -> Self

Attaches a cooperative cancellation token (ADR-012).

Wall-clock timeouts are caller-driven: cancel the token from another thread when a deadline expires.

pub fn execute<'a>(&self, model: &'a Model) -> Result<QueryResults<'a>>

Parses and executes the query against a model.

Parse failures return Error::SparqlParse. Evaluation failures return Error::SparqlEvaluation. Invalid configured base/prefix IRIs return Error::InvalidRdf.

Trait Implementations

impl Clone for Query

fn clone(&self) -> Query

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.