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oxigraph/lib/src/sparql/model.rs

317 lines
9.6 KiB

use crate::model::*;
use crate::sparql::json_results::write_json_results;
use crate::sparql::xml_results::{read_xml_results, write_xml_results};
use crate::Error;
use crate::{FileSyntax, GraphSyntax, Result};
use rand::random;
use rio_api::formatter::TriplesFormatter;
use rio_turtle::{NTriplesFormatter, TurtleFormatter};
use rio_xml::RdfXmlFormatter;
use std::fmt;
use std::io::{BufRead, Write};
use std::rc::Rc;
/// Results of a [SPARQL query](https://www.w3.org/TR/sparql11-query/)
pub enum QueryResult<'a> {
/// Results of a [SELECT](https://www.w3.org/TR/sparql11-query/#select) query
Bindings(QuerySolutionsIterator<'a>),
/// Result of a [ASK](https://www.w3.org/TR/sparql11-query/#ask) query
Boolean(bool),
/// Results of a [CONSTRUCT](https://www.w3.org/TR/sparql11-query/#construct) or [DESCRIBE](https://www.w3.org/TR/sparql11-query/#describe) query
Graph(Box<dyn Iterator<Item = Result<Triple>> + 'a>),
}
impl<'a> QueryResult<'a> {
pub fn read(reader: impl BufRead + 'a, syntax: QueryResultSyntax) -> Result<Self> {
match syntax {
QueryResultSyntax::Xml => read_xml_results(reader),
QueryResultSyntax::Json => Err(Error::msg(
//TODO: implement
"JSON SPARQL results format parsing has not been implemented yet",
)),
}
}
pub fn write<W: Write>(self, writer: W, syntax: QueryResultSyntax) -> Result<W> {
match syntax {
QueryResultSyntax::Xml => write_xml_results(self, writer),
QueryResultSyntax::Json => write_json_results(self, writer),
}
}
pub fn write_graph<W: Write>(self, write: W, syntax: GraphSyntax) -> Result<W> {
if let QueryResult::Graph(triples) = self {
Ok(match syntax {
GraphSyntax::NTriples => {
let mut formatter = NTriplesFormatter::new(write);
for triple in triples {
formatter.format(&(&triple?).into())?;
}
formatter.finish()
}
GraphSyntax::Turtle => {
let mut formatter = TurtleFormatter::new(write);
for triple in triples {
formatter.format(&(&triple?).into())?;
}
formatter.finish()?
}
GraphSyntax::RdfXml => {
let mut formatter = RdfXmlFormatter::new(write)?;
for triple in triples {
formatter.format(&(&triple?).into())?;
}
formatter.finish()?
}
})
} else {
Err(Error::msg(
"Bindings or booleans could not be formatted as an RDF graph",
))
}
}
}
/// [SPARQL query](https://www.w3.org/TR/sparql11-query/) serialization formats
#[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
pub enum QueryResultSyntax {
/// [SPARQL Query Results XML Format](http://www.w3.org/TR/rdf-sparql-XMLres/)
Xml,
/// [SPARQL Query Results JSON Format](https://www.w3.org/TR/sparql11-results-json/)
Json,
}
impl FileSyntax for QueryResultSyntax {
fn iri(self) -> &'static str {
match self {
QueryResultSyntax::Xml => "http://www.w3.org/ns/formats/SPARQL_Results_XML",
QueryResultSyntax::Json => "http://www.w3.org/ns/formats/SPARQL_Results_JSON",
}
}
fn media_type(self) -> &'static str {
match self {
QueryResultSyntax::Xml => "application/sparql-results+xml",
QueryResultSyntax::Json => "application/sparql-results+json",
}
}
fn file_extension(self) -> &'static str {
match self {
QueryResultSyntax::Xml => "srx",
QueryResultSyntax::Json => "srj",
}
}
fn from_mime_type(media_type: &str) -> Option<Self> {
if let Some(base_type) = media_type.split(';').next() {
match base_type {
"application/xml" | "application/sparql-results+xml" => {
Some(QueryResultSyntax::Xml)
}
"application/json" | "application/sparql-results+json" => {
Some(QueryResultSyntax::Json)
}
_ => None,
}
} else {
None
}
}
}
/// An iterator over query result solutions
///
/// ```
/// use oxigraph::{MemoryStore, Result};
/// use oxigraph::sparql::{PreparedQuery, QueryResult, QueryOptions, Variable};
///
/// let store = MemoryStore::new();
/// let prepared_query = store.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())?;
/// if let QueryResult::Bindings(solutions) = prepared_query.exec()? {
/// for solution in solutions {
/// println!("{:?}", solution?.get("s"));
/// }
/// }
/// # Result::Ok(())
/// ```
pub struct QuerySolutionsIterator<'a> {
variables: Rc<Vec<Variable>>,
iter: Box<dyn Iterator<Item = Result<Vec<Option<Term>>>> + 'a>,
}
impl<'a> QuerySolutionsIterator<'a> {
5 years ago
pub fn new(
variables: Vec<Variable>,
iter: Box<dyn Iterator<Item = Result<Vec<Option<Term>>>> + 'a>,
) -> Self {
Self {
variables: Rc::new(variables),
iter,
}
}
/// The variables used in the solutions
///
/// ```
/// use oxigraph::{MemoryStore, Result};
/// use oxigraph::sparql::{PreparedQuery, QueryResult, QueryOptions, Variable};
///
/// let store = MemoryStore::new();
/// let prepared_query = store.prepare_query("SELECT ?s ?o WHERE { ?s ?p ?o }", QueryOptions::default())?;
/// if let QueryResult::Bindings(solutions) = prepared_query.exec()? {
/// assert_eq!(solutions.variables(), &[Variable::new("s"), Variable::new("o")]);
/// }
/// # Result::Ok(())
/// ```
pub fn variables(&self) -> &[Variable] {
&*self.variables
}
#[deprecated(note = "Please directly use QuerySolutionsIterator as an iterator instead")]
pub fn into_values_iter(self) -> Box<dyn Iterator<Item = Result<Vec<Option<Term>>>> + 'a> {
self.iter
}
pub fn destruct(
self,
) -> (
Vec<Variable>,
Box<dyn Iterator<Item = Result<Vec<Option<Term>>>> + 'a>,
) {
((*self.variables).clone(), self.iter)
}
}
impl<'a> Iterator for QuerySolutionsIterator<'a> {
type Item = Result<QuerySolution>;
fn next(&mut self) -> Option<Result<QuerySolution>> {
Some(self.iter.next()?.map(|values| QuerySolution {
values,
variables: self.variables.clone(),
}))
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
/// Tuple associating variables and terms that are the result of a SPARQL query.
///
/// It is the equivalent of a row in SQL.
pub struct QuerySolution {
values: Vec<Option<Term>>,
variables: Rc<Vec<Variable>>,
}
impl QuerySolution {
/// Returns a value for a given position in the tuple (`usize`) or a given variable name (`&str` or `Variable`)
///
/// ```ignore
/// let foo = solution.get("foo"); // Get the value of the variable ?foo if it exists
/// let first = solution.get(1); // Get the value of the second column if it exists
/// ```
pub fn get(&self, index: impl VariableSolutionIndex) -> Option<&Term> {
self.values.get(index.index(self)?).and_then(|e| e.as_ref())
}
/// The number of variables which are bind
pub fn len(&self) -> usize {
self.values.len()
}
/// Is this binding empty?
pub fn is_empty(&self) -> bool {
self.values.is_empty()
}
/// Returns an iterator over bound variables
pub fn iter(&self) -> impl Iterator<Item = (&Variable, &Term)> {
self.values
.iter()
.enumerate()
.filter_map(move |(i, value)| {
if let Some(value) = value {
Some((&self.variables[i], value))
} else {
None
}
})
}
}
/// A utility trait to get values for a given variable or tuple position
pub trait VariableSolutionIndex {
fn index(self, solution: &QuerySolution) -> Option<usize>;
}
impl VariableSolutionIndex for usize {
fn index(self, _: &QuerySolution) -> Option<usize> {
Some(self)
}
}
impl VariableSolutionIndex for &str {
fn index(self, solution: &QuerySolution) -> Option<usize> {
solution.variables.iter().position(|v| v.as_str() == self)
}
}
impl VariableSolutionIndex for &Variable {
fn index(self, solution: &QuerySolution) -> Option<usize> {
solution.variables.iter().position(|v| v == self)
}
}
impl VariableSolutionIndex for Variable {
fn index(self, solution: &QuerySolution) -> Option<usize> {
(&self).index(solution)
}
}
/// A SPARQL query variable
///
/// ```
/// use oxigraph::sparql::Variable;
///
/// assert_eq!(
/// "?foo",
/// Variable::new("foo").to_string()
/// )
/// ```
#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
pub struct Variable {
name: String,
}
impl Variable {
pub fn new(name: impl Into<String>) -> Self {
Variable { name: name.into() }
}
pub fn as_str(&self) -> &str {
&self.name
}
#[deprecated(note = "Please use as_str instead")]
pub fn name(&self) -> Result<&str> {
Ok(self.as_str())
}
pub fn into_string(self) -> String {
self.name
}
pub(crate) fn new_random() -> Self {
Self::new(format!("{:x}", random::<u128>()))
}
}
impl fmt::Display for Variable {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "?{}", self.name)
}
}