Provides a nice API for SPARQL SELECT solutions handling

js/src/store.rs

@@ -116,18 +116,16 @@ impl JsMemoryStore {
             .map_err(to_err)?;
         let results = query.exec().map_err(to_err)?;
         let output = match results {
-            QueryResult::Bindings(bindings) => {
-                let (variables, iter) = bindings.destruct();
-                let variables: Vec<JsValue> =
-                    variables.into_iter().map(|v| v.as_str().into()).collect();
+            QueryResult::Bindings(solutions) => {
                 let results = Array::new();
-                for values in iter {
-                    let values = values.map_err(to_err)?;
+                for solution in solutions {
+                    let solution = solution.map_err(to_err)?;
                     let result = Map::new();
-                    for (variable, value) in variables.iter().zip(values) {
-                        if let Some(value) = value {
-                            result.set(variable, &JsTerm::from(value).into());
-                        }
+                    for (variable, value) in solution.iter() {
+                        result.set(
+                            &variable.as_str().into(),
+                            &JsTerm::from(value.clone()).into(),
+                        );
                     }
                     results.push(&result.into());
                 }

lib/src/lib.rs

@@ -33,9 +33,8 @@
 //!
 //! // SPARQL query
 //! let prepared_query = store.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())?;
-//! let results = prepared_query.exec()?;
-//! if let QueryResult::Bindings(results) = results {
-//!     assert_eq!(results.into_values_iter().next().unwrap()?[0], Some(ex.into()));
+//! if let QueryResult::Bindings(mut solutions) = prepared_query.exec()? {
+//!     assert_eq!(solutions.next().unwrap()?.get("s"), Some(&ex.into()));
 //! }
 //! # Result::Ok(())
 //! ```

lib/src/model/named_node.rs

@@ -13,7 +13,6 @@ use std::fmt;
 ///     NamedNode::parse("http://example.com/foo").unwrap().to_string()
 /// )
 /// ```
-///
 #[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
 pub struct NamedNode {
     iri: String,

lib/src/sparql/eval.rs

@@ -1564,13 +1564,13 @@ impl<'a, S: ReadableEncodedStore + 'a> SimpleEvaluator<S> {
         &'b self,
         iter: EncodedTuplesIterator<'b>,
         variables: Vec<Variable>,
-    ) -> BindingsIterator<'b>
+    ) -> QuerySolutionsIterator<'b>
     where
         'a: 'b,
     {
         let eval = self;
         let tuple_size = variables.len();
-        BindingsIterator::new(
+        QuerySolutionsIterator::new(
             variables,
             Box::new(iter.map(move |values| {
                 let mut result = vec![None; tuple_size];
@@ -1584,40 +1584,25 @@ impl<'a, S: ReadableEncodedStore + 'a> SimpleEvaluator<S> {
         )
     }
 
-    // this is used to encode results froma BindingIterator into an EncodedTuplesIterator. This happens when SERVICE clauses are evaluated
+    // this is used to encode results from a BindingIterator into an EncodedTuplesIterator. This happens when SERVICE clauses are evaluated
     fn encode_bindings<'b>(
         &'b self,
         variables: &'b [Variable],
-        iter: BindingsIterator<'b>,
+        iter: QuerySolutionsIterator<'b>,
     ) -> EncodedTuplesIterator<'b>
     where
         'a: 'b,
     {
-        let (binding_variables, iter) = BindingsIterator::destruct(iter);
-        let mut combined_variables = variables.to_vec();
-        for v in binding_variables.clone() {
-            if !combined_variables.contains(&v) {
-                combined_variables.resize(combined_variables.len() + 1, v);
-            }
-        }
-        Box::new(iter.map(move |terms| {
+        Box::new(iter.map(move |solution| {
             let mut encoder = self.dataset.encoder();
-            let mut encoded_terms = EncodedTuple::with_capacity(combined_variables.len());
-            for (i, term_option) in terms?.into_iter().enumerate() {
-                match term_option {
-                    None => (),
-                    Some(term) => {
-                        if let Ok(encoded) = encoder.encode_term(&term) {
-                            let variable = binding_variables[i].clone();
-                            put_variable_value(
-                                &variable,
-                                &combined_variables,
-                                encoded,
-                                &mut encoded_terms,
-                            )
-                        }
-                    }
-                }
+            let mut encoded_terms = EncodedTuple::with_capacity(variables.len());
+            for (variable, term) in solution?.iter() {
+                put_variable_value(
+                    variable,
+                    variables,
+                    encoder.encode_term(term)?,
+                    &mut encoded_terms,
+                )
             }
             Ok(encoded_terms)
         }))

lib/src/sparql/json_results.rs

@@ -13,11 +13,10 @@ pub fn write_json_results<W: Write>(results: QueryResult<'_>, mut sink: W) -> Re
             sink.write_all(if value { b"true" } else { b"false" })?;
             sink.write_all(b"}")?;
         }
-        QueryResult::Bindings(bindings) => {
-            let (variables, results) = bindings.destruct();
+        QueryResult::Bindings(solutions) => {
             sink.write_all(b"{\"head\":{\"vars\":[")?;
             let mut start_vars = true;
-            for variable in &variables {
+            for variable in solutions.variables() {
                 if start_vars {
                     start_vars = false;
                 } else {
@@ -27,7 +26,7 @@ pub fn write_json_results<W: Write>(results: QueryResult<'_>, mut sink: W) -> Re
             }
             sink.write_all(b"]},\"results\":{\"bindings\":[")?;
             let mut start_bindings = true;
-            for result in results {
+            for solution in solutions {
                 if start_bindings {
                     start_bindings = false;
                 } else {
@@ -35,42 +34,37 @@ pub fn write_json_results<W: Write>(results: QueryResult<'_>, mut sink: W) -> Re
                 }
                 sink.write_all(b"{")?;
 
-                let result = result?;
+                let solution = solution?;
                 let mut start_binding = true;
-                for (i, value) in result.into_iter().enumerate() {
-                    if let Some(term) = value {
-                        if start_binding {
-                            start_binding = false;
-                        } else {
-                            sink.write_all(b",")?;
+                for (variable, value) in solution.iter() {
+                    if start_binding {
+                        start_binding = false;
+                    } else {
+                        sink.write_all(b",")?;
+                    }
+                    write_escaped_json_string(variable.as_str(), &mut sink)?;
+                    match value {
+                        Term::NamedNode(uri) => {
+                            sink.write_all(b":{\"type\":\"uri\",\"value\":")?;
+                            write_escaped_json_string(uri.as_str(), &mut sink)?;
+                            sink.write_all(b"}")?;
                         }
-                        write_escaped_json_string(variables[i].as_str(), &mut sink)?;
-                        match term {
-                            Term::NamedNode(uri) => {
-                                sink.write_all(b":{\"type\":\"uri\",\"value\":")?;
-                                write_escaped_json_string(uri.as_str(), &mut sink)?;
-                                sink.write_all(b"}")?;
-                            }
-                            Term::BlankNode(bnode) => {
-                                sink.write_all(b":{\"type\":\"bnode\",\"value\":")?;
-                                write!(sink, "{}", bnode.as_str())?;
-                                sink.write_all(b"}")?;
-                            }
-                            Term::Literal(literal) => {
-                                sink.write_all(b":{\"type\":\"literal\",\"value\":")?;
-                                write_escaped_json_string(literal.value(), &mut sink)?;
-                                if let Some(language) = literal.language() {
-                                    sink.write_all(b",\"xml:lang\":")?;
-                                    write_escaped_json_string(language, &mut sink)?;
-                                } else if !literal.is_plain() {
-                                    sink.write_all(b",\"datatype\":")?;
-                                    write_escaped_json_string(
-                                        literal.datatype().as_str(),
-                                        &mut sink,
-                                    )?;
-                                }
-                                sink.write_all(b"}")?;
+                        Term::BlankNode(bnode) => {
+                            sink.write_all(b":{\"type\":\"bnode\",\"value\":")?;
+                            write!(sink, "{}", bnode.as_str())?;
+                            sink.write_all(b"}")?;
+                        }
+                        Term::Literal(literal) => {
+                            sink.write_all(b":{\"type\":\"literal\",\"value\":")?;
+                            write_escaped_json_string(literal.value(), &mut sink)?;
+                            if let Some(language) = literal.language() {
+                                sink.write_all(b",\"xml:lang\":")?;
+                                write_escaped_json_string(language, &mut sink)?;
+                            } else if !literal.is_plain() {
+                                sink.write_all(b",\"datatype\":")?;
+                                write_escaped_json_string(literal.datatype().as_str(), &mut sink)?;
                             }
+                            sink.write_all(b"}")?;
                         }
                     }
                 }

lib/src/sparql/mod.rs

@@ -21,7 +21,10 @@ use crate::Result;
 use oxiri::Iri;
 
 pub use crate::sparql::algebra::GraphPattern;
-pub use crate::sparql::model::BindingsIterator;
+pub use crate::sparql::model::QuerySolution;
+pub use crate::sparql::model::QuerySolutionsIterator;
+#[deprecated(note = "Please directly use QuerySolutionsIterator type instead")]
+pub type BindingsIterator<'a> = QuerySolutionsIterator<'a>;
 pub use crate::sparql::model::QueryResult;
 pub use crate::sparql::model::QueryResultSyntax;
 pub use crate::sparql::model::Variable;
@@ -161,17 +164,17 @@ pub trait ServiceHandler {
         &'a self,
         service_name: &NamedNode,
         graph_pattern: &'a GraphPattern,
-    ) -> Result<BindingsIterator<'a>>;
+    ) -> Result<QuerySolutionsIterator<'a>>;
 }
 
-impl<F: for<'a> Fn(&NamedNode, &'a GraphPattern) -> Result<BindingsIterator<'a>>> ServiceHandler
-    for F
+impl<F: for<'a> Fn(&NamedNode, &'a GraphPattern) -> Result<QuerySolutionsIterator<'a>>>
+    ServiceHandler for F
 {
     fn handle<'a>(
         &'a self,
         service_name: &NamedNode,
         graph_pattern: &'a GraphPattern,
-    ) -> Result<BindingsIterator<'a>> {
+    ) -> Result<QuerySolutionsIterator<'a>> {
         self(service_name, graph_pattern)
     }
 }
@@ -179,7 +182,11 @@ impl<F: for<'a> Fn(&NamedNode, &'a GraphPattern) -> Result<BindingsIterator<'a>>
 struct EmptyServiceHandler;
 
 impl ServiceHandler for EmptyServiceHandler {
-    fn handle<'a>(&'a self, _: &NamedNode, _: &'a GraphPattern) -> Result<BindingsIterator<'a>> {
+    fn handle<'a>(
+        &'a self,
+        _: &NamedNode,
+        _: &'a GraphPattern,
+    ) -> Result<QuerySolutionsIterator<'a>> {
         Err(Error::msg("The SERVICE feature is not implemented"))
     }
 }

lib/src/sparql/model.rs

@@ -9,11 +9,12 @@ 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(BindingsIterator<'a>),
+    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
@@ -119,24 +120,55 @@ impl FileSyntax for QueryResultSyntax {
     }
 }
 
-/// An iterator over results bindings
-pub struct BindingsIterator<'a> {
-    variables: Vec<Variable>,
+/// 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> BindingsIterator<'a> {
+impl<'a> QuerySolutionsIterator<'a> {
     pub fn new(
         variables: Vec<Variable>,
         iter: Box<dyn Iterator<Item = Result<Vec<Option<Term>>>> + 'a>,
     ) -> Self {
-        Self { variables, iter }
+        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
     }
@@ -147,11 +179,108 @@ impl<'a> BindingsIterator<'a> {
         Vec<Variable>,
         Box<dyn Iterator<Item = Result<Vec<Option<Term>>>> + 'a>,
     ) {
-        (self.variables, self.iter)
+        ((*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,
@@ -166,7 +295,7 @@ impl Variable {
         &self.name
     }
 
-    #[deprecated]
+    #[deprecated(note = "Please use as_str instead")]
     pub fn name(&self) -> Result<&str> {
         Ok(self.as_str())
     }

lib/src/sparql/xml_results.rs

@@ -35,63 +35,58 @@ pub fn write_xml_results<W: Write>(results: QueryResult<'_>, sink: W) -> Result<
             writer.write_event(Event::End(BytesEnd::borrowed(b"boolean")))?;
             writer.write_event(Event::End(BytesEnd::borrowed(b"sparql")))?;
         }
-        QueryResult::Bindings(bindings) => {
-            let (variables, results) = bindings.destruct();
+        QueryResult::Bindings(solutions) => {
             writer.write_event(Event::Decl(BytesDecl::new(b"1.0", None, None)))?;
             let mut sparql_open = BytesStart::borrowed_name(b"sparql");
             sparql_open.push_attribute(("xmlns", "http://www.w3.org/2005/sparql-results#"));
             writer.write_event(Event::Start(sparql_open))?;
             writer.write_event(Event::Start(BytesStart::borrowed_name(b"head")))?;
-            for variable in &variables {
+            for variable in solutions.variables() {
                 let mut variable_tag = BytesStart::borrowed_name(b"variable");
                 variable_tag.push_attribute(("name", variable.as_str()));
                 writer.write_event(Event::Empty(variable_tag))?;
             }
             writer.write_event(Event::End(BytesEnd::borrowed(b"head")))?;
             writer.write_event(Event::Start(BytesStart::borrowed_name(b"results")))?;
-            for result in results {
-                let result = result?;
+            for solution in solutions {
+                let solution = solution?;
                 writer.write_event(Event::Start(BytesStart::borrowed_name(b"result")))?;
-                for (i, value) in result.into_iter().enumerate() {
-                    if let Some(term) = value {
-                        let mut binding_tag = BytesStart::borrowed_name(b"binding");
-                        binding_tag.push_attribute(("name", variables[i].as_str()));
-                        writer.write_event(Event::Start(binding_tag))?;
-                        match term {
-                            Term::NamedNode(uri) => {
-                                writer
-                                    .write_event(Event::Start(BytesStart::borrowed_name(b"uri")))?;
-                                writer.write_event(Event::Text(BytesText::from_plain_str(
-                                    uri.as_str(),
-                                )))?;
-                                writer.write_event(Event::End(BytesEnd::borrowed(b"uri")))?;
-                            }
-                            Term::BlankNode(bnode) => {
-                                writer.write_event(Event::Start(BytesStart::borrowed_name(
-                                    b"bnode",
-                                )))?;
-                                writer.write_event(Event::Text(BytesText::from_plain_str(
-                                    bnode.as_str(),
-                                )))?;
-                                writer.write_event(Event::End(BytesEnd::borrowed(b"bnode")))?;
-                            }
-                            Term::Literal(literal) => {
-                                let mut literal_tag = BytesStart::borrowed_name(b"literal");
-                                if let Some(language) = literal.language() {
-                                    literal_tag.push_attribute(("xml:lang", language));
-                                } else if !literal.is_plain() {
-                                    literal_tag
-                                        .push_attribute(("datatype", literal.datatype().as_str()));
-                                }
-                                writer.write_event(Event::Start(literal_tag))?;
-                                writer.write_event(Event::Text(BytesText::from_plain_str(
-                                    literal.value(),
-                                )))?;
-                                writer.write_event(Event::End(BytesEnd::borrowed(b"literal")))?;
+                for (variable, value) in solution.iter() {
+                    let mut binding_tag = BytesStart::borrowed_name(b"binding");
+                    binding_tag.push_attribute(("name", variable.as_str()));
+                    writer.write_event(Event::Start(binding_tag))?;
+                    match value {
+                        Term::NamedNode(uri) => {
+                            writer.write_event(Event::Start(BytesStart::borrowed_name(b"uri")))?;
+                            writer.write_event(Event::Text(BytesText::from_plain_str(
+                                uri.as_str(),
+                            )))?;
+                            writer.write_event(Event::End(BytesEnd::borrowed(b"uri")))?;
+                        }
+                        Term::BlankNode(bnode) => {
+                            writer
+                                .write_event(Event::Start(BytesStart::borrowed_name(b"bnode")))?;
+                            writer.write_event(Event::Text(BytesText::from_plain_str(
+                                bnode.as_str(),
+                            )))?;
+                            writer.write_event(Event::End(BytesEnd::borrowed(b"bnode")))?;
+                        }
+                        Term::Literal(literal) => {
+                            let mut literal_tag = BytesStart::borrowed_name(b"literal");
+                            if let Some(language) = literal.language() {
+                                literal_tag.push_attribute(("xml:lang", language));
+                            } else if !literal.is_plain() {
+                                literal_tag
+                                    .push_attribute(("datatype", literal.datatype().as_str()));
                             }
+                            writer.write_event(Event::Start(literal_tag))?;
+                            writer.write_event(Event::Text(BytesText::from_plain_str(
+                                literal.value(),
+                            )))?;
+                            writer.write_event(Event::End(BytesEnd::borrowed(b"literal")))?;
                         }
-                        writer.write_event(Event::End(BytesEnd::borrowed(b"binding")))?;
                     }
+                    writer.write_event(Event::End(BytesEnd::borrowed(b"binding")))?;
                 }
                 writer.write_event(Event::End(BytesEnd::borrowed(b"result")))?;
             }
@@ -175,7 +170,7 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                         for (i,var) in variables.iter().enumerate() {
                             mapping.insert(var.as_bytes().to_vec(), i);
                         }
-                        return Ok(QueryResult::Bindings(BindingsIterator::new(
+                        return Ok(QueryResult::Bindings(QuerySolutionsIterator::new(
                             variables.into_iter().map(Variable::new).collect(),
                             Box::new(ResultsIterator {
                                 reader,
@@ -214,7 +209,7 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                 },
                 State::AfterHead => {
                     if event.name() == b"results" {
-                        return Ok(QueryResult::Bindings(BindingsIterator::new(
+                        return Ok(QueryResult::Bindings(QuerySolutionsIterator::new(
                             variables.into_iter().map(Variable::new).collect(),
                             Box::new(empty()),
                         )))

lib/src/store/memory.rs

@@ -31,9 +31,8 @@ use std::sync::{Arc, RwLock, RwLockReadGuard, RwLockWriteGuard};
 ///
 /// // SPARQL query
 /// let prepared_query = store.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())?;
-/// let results = prepared_query.exec()?;
-/// if let QueryResult::Bindings(results) = results {
-///     assert_eq!(results.into_values_iter().next().unwrap()?[0], Some(ex.into()));
+/// if let QueryResult::Bindings(mut solutions) = prepared_query.exec()? {
+///     assert_eq!(solutions.next().unwrap()?.get("s"), Some(&ex.into()));
 /// }
 /// # Result::Ok(())
 /// ```
@@ -88,9 +87,8 @@ impl MemoryStore {
     ///
     /// // SPARQL query
     /// let prepared_query = store.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())?;
-    /// let results = prepared_query.exec()?;
-    /// if let QueryResult::Bindings(results) = results {
-    ///     assert_eq!(results.into_values_iter().next().unwrap()?[0], Some(ex.into()));
+    /// if let QueryResult::Bindings(mut solutions) = prepared_query.exec()? {
+    ///     assert_eq!(solutions.next().unwrap()?.get("s"), Some(&ex.into()));
     /// }
     /// # Result::Ok(())
     /// ```

lib/src/store/rocksdb.rs

@@ -37,8 +37,8 @@ use std::sync::Arc;
 /// // SPARQL query
 /// let prepared_query = store.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())?;
 /// let results = prepared_query.exec()?;
-/// if let QueryResult::Bindings(results) = results {
-///     assert_eq!(results.into_values_iter().next().unwrap()?[0], Some(ex.into()));
+/// if let QueryResult::Bindings(mut solutions) =  results {
+///     assert_eq!(solutions.next().unwrap()?.get("s"), Some(&ex.into()));
 /// }
 /// #
 /// # }

lib/src/store/sled.rs

@@ -36,9 +36,8 @@ use std::str;
 ///
 /// // SPARQL query
 /// let prepared_query = store.prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())?;
-/// let results = prepared_query.exec()?;
-/// if let QueryResult::Bindings(results) = results {
-///     assert_eq!(results.into_values_iter().next().unwrap()?[0], Some(ex.into()));
+/// if let QueryResult::Bindings(mut solutions) = prepared_query.exec()? {
+///     assert_eq!(solutions.next().unwrap()?.get("s"), Some(&ex.into()));
 /// }
 /// #
 /// # }

lib/tests/service_test_cases.rs

@@ -11,7 +11,7 @@ fn simple_service_test() {
             &'a self,
             _: &NamedNode,
             graph_pattern: &'a GraphPattern,
-        ) -> Result<BindingsIterator<'a>> {
+        ) -> Result<QuerySolutionsIterator<'a>> {
             let triples =
                 b"<http://example.com/s> <http://example.com/p> <http://example.com/o> .".as_ref();
             do_pattern(triples, graph_pattern, QueryOptions::default())
@@ -30,16 +30,16 @@ fn simple_service_test() {
     .to_string();
 
     let options = QueryOptions::default().with_service_handler(TestServiceHandler);
-    let results = do_query(b"".as_ref(), query, options).unwrap();
-    let collected = results
-        .into_values_iter()
-        .map(move |b| b.unwrap())
+    let collected = do_query(b"".as_ref(), query, options)
+        .unwrap()
+        .map(|b| {
+            b.unwrap()
+                .iter()
+                .map(|(_, v)| v.clone())
+                .collect::<Vec<_>>()
+        })
         .collect::<Vec<_>>();
-    let solution = vec![vec![
-        Some(ex(String::from("s"))),
-        Some(ex(String::from("p"))),
-        Some(ex(String::from("o"))),
-    ]];
+    let solution = vec![vec![ex("s"), ex("p"), ex("o")]];
     assert_eq!(collected, solution);
 }
 
@@ -52,7 +52,7 @@ fn two_service_test() {
             &'a self,
             named_node: &NamedNode,
             graph_pattern: &'a GraphPattern,
-        ) -> Result<BindingsIterator<'a>> {
+        ) -> Result<QuerySolutionsIterator<'a>> {
             let service1 = NamedNode::parse("http://service1.org").unwrap();
             let service2 = NamedNode::parse("http://service2.org").unwrap();
             if named_node == &service1 {
@@ -93,20 +93,18 @@ fn two_service_test() {
     .to_string();
 
     let options = QueryOptions::default().with_service_handler(TwoServiceTest);
-    let results = do_query(b"".as_ref(), query, options).unwrap();
-    let collected = results
-        .into_values_iter()
-        .map(move |b| b.unwrap())
+    let collected = do_query(b"".as_ref(), query, options)
+        .unwrap()
+        .map(|b| {
+            b.unwrap()
+                .iter()
+                .map(|(_, v)| v.clone())
+                .collect::<Vec<_>>()
+        })
         .collect::<Vec<_>>();
     let solution = vec![
-        vec![
-            Some(literal("Alice".to_string())),
-            Some(mailto("alice@example.com".to_string())),
-        ],
-        vec![
-            Some(literal("Bob".to_string())),
-            Some(mailto("bob@example.com".to_string())),
-        ],
+        vec![literal("Alice"), mailto("alice@example.com")],
+        vec![literal("Bob"), mailto("bob@example.com")],
     ];
     assert_eq!(collected, solution);
 }
@@ -120,7 +118,7 @@ fn silent_service_empty_set_test() {
             &'a self,
             _: &NamedNode,
             _: &'a GraphPattern,
-        ) -> Result<BindingsIterator<'a>> {
+        ) -> Result<QuerySolutionsIterator<'a>> {
             Err(Error::msg("This is supposed to fail"))
         }
     }
@@ -141,12 +139,7 @@ fn silent_service_empty_set_test() {
 
     let triples = b"".as_ref();
     let options = QueryOptions::default().with_service_handler(ServiceTest);
-    let results = do_query(triples, query, options).unwrap();
-    let collected = results
-        .into_values_iter()
-        .map(move |b| b.unwrap())
-        .collect::<Vec<_>>();
-    assert_eq!(collected.len(), 1);
+    assert_eq!(do_query(triples, query, options).unwrap().count(), 1);
 }
 
 #[test]
@@ -158,7 +151,7 @@ fn non_silent_service_test() {
             &'a self,
             _: &NamedNode,
             _: &'a GraphPattern,
-        ) -> Result<BindingsIterator<'a>> {
+        ) -> Result<QuerySolutionsIterator<'a>> {
             Err(Error::msg("This is supposed to fail"))
         }
     }
@@ -179,26 +172,22 @@ fn non_silent_service_test() {
 
     let triples = b"".as_ref();
     let options = QueryOptions::default().with_service_handler(ServiceTest);
-    let results = do_query(triples, query, options).unwrap();
-    let result = results.into_values_iter().next();
-    match result {
-        Some(Err(_)) => assert_eq!(true, true),
-        _ => assert_eq!(
-            true, false,
-            "This should have been an error since the service fails"
-        ),
+    let mut solutions = do_query(triples, query, options).unwrap();
+    if let Some(Err(_)) = solutions.next() {
+    } else {
+        panic!("This should have been an error since the service fails")
     }
 }
 
-fn ex(id: String) -> Term {
-    Term::NamedNode(NamedNode::parse(format!("http://example.com/{}", &id)).unwrap())
+fn ex(id: &str) -> Term {
+    Term::NamedNode(NamedNode::parse(format!("http://example.com/{}", id)).unwrap())
 }
 
-fn mailto(id: String) -> Term {
-    Term::NamedNode(NamedNode::parse(format!("mailto:{}", &id)).unwrap())
+fn mailto(id: &str) -> Term {
+    Term::NamedNode(NamedNode::parse(format!("mailto:{}", id)).unwrap())
 }
 
-fn literal(str: String) -> Term {
+fn literal(str: &str) -> Term {
     Term::Literal(Literal::new_simple_literal(str))
 }
 
@@ -214,13 +203,13 @@ fn query_store<'a>(
     store: MemoryStore,
     query: String,
     options: QueryOptions<'a>,
-) -> Result<BindingsIterator<'a>> {
+) -> Result<QuerySolutionsIterator<'a>> {
     match store.prepare_query(&query, options)?.exec()? {
         QueryResult::Bindings(iterator) => {
-            let (varaibles, iter) = iterator.destruct();
+            let (variables, iter) = iterator.destruct();
             let collected = iter.collect::<Vec<_>>();
-            Ok(BindingsIterator::new(
-                varaibles,
+            Ok(QuerySolutionsIterator::new(
+                variables,
                 Box::new(collected.into_iter()),
             ))
         }
@@ -232,7 +221,7 @@ fn pattern_store<'a>(
     store: MemoryStore,
     pattern: &'a GraphPattern,
     options: QueryOptions<'a>,
-) -> Result<BindingsIterator<'a>> {
+) -> Result<QuerySolutionsIterator<'a>> {
     match store
         .prepare_query_from_pattern(&pattern, options)?
         .exec()?
@@ -240,7 +229,7 @@ fn pattern_store<'a>(
         QueryResult::Bindings(iterator) => {
             let (varaibles, iter) = iterator.destruct();
             let collected = iter.collect::<Vec<_>>();
-            Ok(BindingsIterator::new(
+            Ok(QuerySolutionsIterator::new(
                 varaibles,
                 Box::new(collected.into_iter()),
             ))
@@ -253,7 +242,7 @@ fn do_query<'a>(
     reader: impl BufRead,
     query: String,
     options: QueryOptions<'a>,
-) -> Result<BindingsIterator<'a>> {
+) -> Result<QuerySolutionsIterator<'a>> {
     let store = make_store(reader)?;
     query_store(store, query, options)
 }
@@ -262,7 +251,7 @@ fn do_pattern<'a>(
     reader: impl BufRead,
     pattern: &'a GraphPattern,
     options: QueryOptions<'a>,
-) -> Result<BindingsIterator<'a>> {
+) -> Result<QuerySolutionsIterator<'a>> {
     let store = make_store(reader)?;
     pattern_store(store, pattern, options)
 }

lib/tests/sparql_test_cases.rs

@@ -348,7 +348,7 @@ fn to_graph(result: QueryResult<'_>, with_order: bool) -> Result<SimpleGraph> {
             ));
             Ok(graph)
         }
-        QueryResult::Bindings(bindings) => {
+        QueryResult::Bindings(solutions) => {
             let mut graph = SimpleGraph::default();
             let result_set = BlankNode::default();
             graph.insert(Triple::new(
@@ -356,33 +356,30 @@ fn to_graph(result: QueryResult<'_>, with_order: bool) -> Result<SimpleGraph> {
                 rdf::TYPE.clone(),
                 rs::RESULT_SET.clone(),
             ));
-            let (variables, iter) = bindings.destruct();
-            for variable in &variables {
+            for variable in solutions.variables() {
                 graph.insert(Triple::new(
                     result_set,
                     rs::RESULT_VARIABLE.clone(),
                     Literal::new_simple_literal(variable.as_str()),
                 ));
             }
-            for (i, binding_values) in iter.enumerate() {
-                let binding_values = binding_values?;
-                let solution = BlankNode::default();
-                graph.insert(Triple::new(result_set, rs::SOLUTION.clone(), solution));
-                for i in 0..variables.len() {
-                    if let Some(ref value) = binding_values[i] {
-                        let binding = BlankNode::default();
-                        graph.insert(Triple::new(solution, rs::BINDING.clone(), binding));
-                        graph.insert(Triple::new(binding, rs::VALUE.clone(), value.clone()));
-                        graph.insert(Triple::new(
-                            binding,
-                            rs::VARIABLE.clone(),
-                            Literal::new_simple_literal(variables[i].as_str()),
-                        ));
-                    }
+            for (i, solution) in solutions.enumerate() {
+                let solution = solution?;
+                let solution_id = BlankNode::default();
+                graph.insert(Triple::new(result_set, rs::SOLUTION.clone(), solution_id));
+                for (variable, value) in solution.iter() {
+                    let binding = BlankNode::default();
+                    graph.insert(Triple::new(solution_id, rs::BINDING.clone(), binding));
+                    graph.insert(Triple::new(binding, rs::VALUE.clone(), value.clone()));
+                    graph.insert(Triple::new(
+                        binding,
+                        rs::VARIABLE.clone(),
+                        Literal::new_simple_literal(variable.as_str()),
+                    ));
                 }
                 if with_order {
                     graph.insert(Triple::new(
-                        solution,
+                        solution_id,
                         rs::INDEX.clone(),
                         Literal::from((i + 1) as i128),
                     ));
@@ -720,7 +717,7 @@ impl ServiceHandler for StaticServiceHandler {
         &'a self,
         service_name: &NamedNode,
         graph_pattern: &'a GraphPattern,
-    ) -> Result<BindingsIterator<'a>> {
+    ) -> Result<QuerySolutionsIterator<'a>> {
         if let QueryResult::Bindings(iterator) = self
             .services
             .get(service_name)
@@ -731,10 +728,10 @@ impl ServiceHandler for StaticServiceHandler {
             )?
             .exec()?
         {
-            //TODO: very hugly
+            //TODO: very ugly
             let (variables, iter) = iterator.destruct();
             let collected = iter.collect::<Vec<_>>();
-            Ok(BindingsIterator::new(
+            Ok(QuerySolutionsIterator::new(
                 variables,
                 Box::new(collected.into_iter()),
             ))

lib/tests/wasm.rs

@@ -22,18 +22,17 @@ mod test {
         let prepared_query = store
             .prepare_query("SELECT ?s WHERE { ?s ?p ?o }", QueryOptions::default())
             .unwrap();
-        let results = prepared_query.exec().unwrap();
-        if let QueryResult::Bindings(results) = results {
+        if let QueryResult::Bindings(mut solutions) = prepared_query.exec().unwrap() {
             assert_eq!(
-                results.into_values_iter().next().unwrap().unwrap()[0],
-                Some(ex.into())
+                solutions.next().unwrap().unwrap().get("s"),
+                Some(&ex.into())
             );
         }
     }
 
     #[wasm_bindgen_test]
     fn now() {
-        if let QueryResult::Bindings(results) = MemoryStore::default()
+        if let QueryResult::Bindings(solutions) = MemoryStore::default()
             .prepare_query(
                 "SELECT (YEAR(NOW()) AS ?y) WHERE {}",
                 QueryOptions::default(),
@@ -42,8 +41,7 @@ mod test {
             .exec()
             .unwrap()
         {
-            if let Some(Term::Literal(l)) = &results.into_values_iter().next().unwrap().unwrap()[0]
-            {
+            if let Some(Term::Literal(l)) = solutions.next().unwrap().unwrap().get(0) {
                 let year = i64::from_str(l.value()).unwrap();
                 assert!(2020 <= year && year <= 2100);
             }