Makes Oxigraph store "graph aware"

CHANGELOG.md

@@ -4,10 +4,10 @@
 - [SPARQL 1.1 Update](https://www.w3.org/TR/sparql11-update/) support for Rust, Python and JavaScript. All store-like classes now provide an `update` method.
 - [SPARQL 1.1 Query Results CSV and TSV Formats](https://www.w3.org/TR/sparql11-results-csv-tsv/) serializers and TSV format parser.
 - The SPARQL Query and Update algebra is now public.
+- The stores are now "graph aware" i.e. it is possible to create and keep empty named graphs.
 - A simple built-in HTTP client. In the Rust library, is disabled by default behind the `http_client` feature. It powers SPARQL federation and SPARQL UPDATE `LOAD` operations.
 - `std::str::FromStr` implementations to `NamedNode`, `BlankNode`, `Literal`, `Term` and `Variable` allowing to easily parse Turtle/SPARQL serialization of these terms.
 - Optional Sled storage for `oxigraph_server`.
-- `(Memory|RocksDB|Sled)Store::drop_graph` and `(Memory|RocksDB|Sled)Store::clear`.
 
 ### Removed
 - The `default_graph_uris` and `named_graph_uris` parameters from `pyoxigraph` `query` methods.

lib/src/sparql/dataset.rs

@@ -6,7 +6,7 @@ use crate::store::numeric_encoder::{
 use crate::store::ReadableEncodedStore;
 use lasso::{Rodeo, Spur};
 use std::cell::RefCell;
-use std::iter::empty;
+use std::iter::{empty, once, Once};
 
 pub(crate) struct DatasetView<S: ReadableEncodedStore> {
     store: S,
@@ -182,6 +182,7 @@ impl<S: ReadableEncodedStore> StrLookup for DatasetView<S> {
 impl<S: ReadableEncodedStore> ReadableEncodedStore for DatasetView<S> {
     type QuadsIter =
         Box<dyn Iterator<Item = Result<EncodedQuad<DatasetStrId<S::StrId>>, EvaluationError>>>;
+    type GraphsIter = Once<Result<EncodedTerm<DatasetStrId<S::StrId>>, EvaluationError>>;
 
     fn encoded_quads_for_pattern(
         &self,
@@ -199,6 +200,21 @@ impl<S: ReadableEncodedStore> ReadableEncodedStore for DatasetView<S> {
             Box::new(empty())
         }
     }
+
+    fn encoded_named_graphs(&self) -> Self::GraphsIter {
+        once(Err(EvaluationError::msg(
+            "Graphs lookup is not implemented by DatasetView",
+        )))
+    }
+
+    fn contains_encoded_named_graph(
+        &self,
+        _: EncodedTerm<Self::StrId>,
+    ) -> Result<bool, EvaluationError> {
+        Err(EvaluationError::msg(
+            "Graphs lookup is not implemented by DatasetView",
+        ))
+    }
 }
 
 fn map_iter<'a, I: StrId>(

lib/src/sparql/parser.rs

@@ -986,7 +986,7 @@ parser! {
                 Vec::new() // identity case
             } else {
                 let bgp = GraphPattern::BGP(vec![TriplePattern::new(Variable::new_unchecked("s"), Variable::new_unchecked("p"), Variable::new_unchecked("o"))]);
-                vec![GraphUpdateOperation::Drop { silent, graph: to.clone().map_or(GraphTarget::DefaultGraph, GraphTarget::NamedNode) }, copy_graph(from.clone(), to.map(NamedNodeOrVariable::NamedNode)), GraphUpdateOperation::Drop { silent, graph: from.map_or(GraphTarget::DefaultGraph, GraphTarget::NamedNode) }]
+                vec![GraphUpdateOperation::Drop { silent: true, graph: to.clone().map_or(GraphTarget::DefaultGraph, GraphTarget::NamedNode) }, copy_graph(from.clone(), to.map(NamedNodeOrVariable::NamedNode)), GraphUpdateOperation::Drop { silent, graph: from.map_or(GraphTarget::DefaultGraph, GraphTarget::NamedNode) }]
             }
         }
 
@@ -997,7 +997,7 @@ parser! {
                 Vec::new() // identity case
             } else {
                 let bgp = GraphPattern::BGP(vec![TriplePattern::new(Variable::new_unchecked("s"), Variable::new_unchecked("p"), Variable::new_unchecked("o"))]);
-                vec![GraphUpdateOperation::Drop { silent, graph: to.clone().map_or(GraphTarget::DefaultGraph, GraphTarget::NamedNode) }, copy_graph(from, to.map(NamedNodeOrVariable::NamedNode))]
+                vec![GraphUpdateOperation::Drop { silent: true, graph: to.clone().map_or(GraphTarget::DefaultGraph, GraphTarget::NamedNode) }, copy_graph(from, to.map(NamedNodeOrVariable::NamedNode))]
             }
         }
 

lib/src/sparql/update.rs

@@ -81,9 +81,9 @@ where
                     Ok(())
                 }
             }
-            GraphUpdateOperation::Clear { graph, .. } => self.eval_clear(graph),
-            GraphUpdateOperation::Create { .. } => Ok(()),
-            GraphUpdateOperation::Drop { graph, .. } => self.eval_clear(graph),
+            GraphUpdateOperation::Clear { graph, silent } => self.eval_clear(graph, *silent),
+            GraphUpdateOperation::Create { graph, silent } => self.eval_create(graph, *silent),
+            GraphUpdateOperation::Drop { graph, silent } => self.eval_drop(graph, *silent),
         }
     }
 
@@ -227,55 +227,129 @@ where
         Ok(())
     }
 
-    fn eval_clear(&mut self, graph: &GraphTarget) -> Result<(), EvaluationError> {
+    fn eval_create(&mut self, graph: &NamedNode, silent: bool) -> Result<(), EvaluationError> {
+        let encoded_graph_name = self
+            .write
+            .encode_named_node(graph.as_ref())
+            .map_err(to_eval_error)?;
+        if self
+            .read
+            .contains_encoded_named_graph(encoded_graph_name)
+            .map_err(to_eval_error)?
+        {
+            if silent {
+                Ok(())
+            } else {
+                Err(EvaluationError::msg(format!(
+                    "The graph {} already exists",
+                    graph
+                )))
+            }
+        } else {
+            self.write
+                .insert_encoded_named_graph(encoded_graph_name)
+                .map_err(to_eval_error)
+        }
+    }
+
+    fn eval_clear(&mut self, graph: &GraphTarget, silent: bool) -> Result<(), EvaluationError> {
         match graph {
-            GraphTarget::NamedNode(graph) => {
-                if let Some(graph) = self
+            GraphTarget::NamedNode(graph_name) => {
+                if let Some(graph_name) = self
                     .read
-                    .get_encoded_named_node(graph.into())
+                    .get_encoded_named_node(graph_name.as_ref())
                     .map_err(to_eval_error)?
                 {
-                    for quad in self
+                    if self
                         .read
-                        .encoded_quads_for_pattern(None, None, None, Some(graph))
+                        .contains_encoded_named_graph(graph_name)
+                        .map_err(to_eval_error)?
                     {
-                        self.write
-                            .remove_encoded(&quad.map_err(to_eval_error)?)
-                            .map_err(to_eval_error)?;
+                        return self
+                            .write
+                            .clear_encoded_graph(graph_name)
+                            .map_err(to_eval_error);
                     }
+                }
+                if silent {
+                    Ok(())
                 } else {
-                    //we do not track created graph so it's fine
+                    Err(EvaluationError::msg(format!(
+                        "The graph {} does not exists",
+                        graph
+                    )))
+                }
+            }
+            GraphTarget::DefaultGraph => self
+                .write
+                .clear_encoded_graph(EncodedTerm::DefaultGraph)
+                .map_err(to_eval_error),
+            GraphTarget::NamedGraphs => {
+                // TODO: optimize?
+                for graph in self.read.encoded_named_graphs() {
+                    self.write
+                        .clear_encoded_graph(graph.map_err(to_eval_error)?)
+                        .map_err(to_eval_error)?;
                 }
+                Ok(())
             }
-            GraphTarget::DefaultGraph => {
-                for quad in self.read.encoded_quads_for_pattern(
-                    None,
-                    None,
-                    None,
-                    Some(EncodedTerm::DefaultGraph),
-                ) {
+            GraphTarget::AllGraphs => {
+                // TODO: optimize?
+                for graph in self.read.encoded_named_graphs() {
                     self.write
-                        .remove_encoded(&quad.map_err(to_eval_error)?)
+                        .clear_encoded_graph(graph.map_err(to_eval_error)?)
                         .map_err(to_eval_error)?;
                 }
+                self.write
+                    .clear_encoded_graph(EncodedTerm::DefaultGraph)
+                    .map_err(to_eval_error)
             }
-            GraphTarget::NamedGraphs => {
-                for quad in self.read.encoded_quads_for_pattern(None, None, None, None) {
-                    let quad = quad.map_err(to_eval_error)?;
-                    if !quad.graph_name.is_default_graph() {
-                        self.write.remove_encoded(&quad).map_err(to_eval_error)?;
+        }
+    }
+
+    fn eval_drop(&mut self, graph: &GraphTarget, silent: bool) -> Result<(), EvaluationError> {
+        match graph {
+            GraphTarget::NamedNode(graph_name) => {
+                if let Some(graph_name) = self
+                    .read
+                    .get_encoded_named_node(graph_name.as_ref())
+                    .map_err(to_eval_error)?
+                {
+                    if self
+                        .read
+                        .contains_encoded_named_graph(graph_name)
+                        .map_err(to_eval_error)?
+                    {
+                        return self
+                            .write
+                            .remove_encoded_named_graph(graph_name)
+                            .map_err(to_eval_error);
                     }
                 }
+                if silent {
+                    Ok(())
+                } else {
+                    Err(EvaluationError::msg(format!(
+                        "The graph {} does not exists",
+                        graph
+                    )))
+                }
             }
-            GraphTarget::AllGraphs => {
-                for quad in self.read.encoded_quads_for_pattern(None, None, None, None) {
+            GraphTarget::DefaultGraph => self
+                .write
+                .clear_encoded_graph(EncodedTerm::DefaultGraph)
+                .map_err(to_eval_error),
+            GraphTarget::NamedGraphs => {
+                // TODO: optimize?
+                for graph in self.read.encoded_named_graphs() {
                     self.write
-                        .remove_encoded(&quad.map_err(to_eval_error)?)
+                        .remove_encoded_named_graph(graph.map_err(to_eval_error)?)
                         .map_err(to_eval_error)?;
                 }
+                Ok(())
             }
-        };
-        Ok(())
+            GraphTarget::AllGraphs => self.write.clear().map_err(to_eval_error),
+        }
     }
 
     fn encode_quad_for_insertion(

lib/src/store/binary_encoder.rs

@@ -11,7 +11,7 @@ use std::mem::size_of;
 type EncodedTerm = crate::store::numeric_encoder::EncodedTerm<StrHash>;
 type EncodedQuad = crate::store::numeric_encoder::EncodedQuad<StrHash>;
 
-pub const LATEST_STORAGE_VERSION: u64 = 0;
+pub const LATEST_STORAGE_VERSION: u64 = 1;
 pub const WRITTEN_TERM_MAX_SIZE: usize = size_of::<u8>() + 2 * size_of::<StrHash>();
 
 // Encoded term type blocks
@@ -111,6 +111,10 @@ impl QuadEncoding {
     }
 }
 
+pub fn decode_term(buffer: &[u8]) -> Result<EncodedTerm, io::Error> {
+    Cursor::new(&buffer).read_term()
+}
+
 pub trait TermReader {
     fn read_term(&mut self) -> Result<EncodedTerm, io::Error>;
 

lib/src/store/memory.rs

@@ -455,7 +455,75 @@ impl MemoryStore {
         dump_dataset(self.iter().map(Ok), writer, format)
     }
 
-    /// Removes a graph from this store.
+    /// Returns all the store named graphs
+    ///
+    /// Usage example:
+    /// ```
+    /// use oxigraph::MemoryStore;
+    /// use oxigraph::model::{NamedNode, Quad, NamedOrBlankNode};
+    ///
+    /// let ex = NamedNode::new("http://example.com")?;
+    /// let store = MemoryStore::new();
+    /// store.insert(Quad::new(ex.clone(), ex.clone(), ex.clone(), ex.clone()));
+    /// store.insert(Quad::new(ex.clone(), ex.clone(), ex.clone(), None));     
+    /// assert_eq!(vec![NamedOrBlankNode::from(ex)], store.named_graphs().collect::<Vec<_>>());
+    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
+    /// ```
+    pub fn named_graphs(&self) -> MemoryGraphNameIter {
+        MemoryGraphNameIter {
+            iter: self.encoded_named_graphs(),
+            store: self.clone(),
+        }
+    }
+
+    /// Checks if the store contains a given graph
+    ///
+    /// Usage example:
+    /// ```
+    /// use oxigraph::MemoryStore;
+    /// use oxigraph::model::{NamedNode, Quad};
+    ///
+    /// let ex = NamedNode::new("http://example.com")?;
+    /// let store = MemoryStore::new();
+    /// store.insert(Quad::new(ex.clone(), ex.clone(), ex.clone(), ex.clone()));
+    /// assert!(store.contains_named_graph(&ex));
+    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
+    /// ```
+    pub fn contains_named_graph<'a>(&self, graph_name: impl Into<NamedOrBlankNodeRef<'a>>) -> bool {
+        if let Some(graph_name) = self
+            .get_encoded_named_or_blank_node(graph_name.into())
+            .unwrap_infallible()
+        {
+            self.contains_encoded_named_graph(graph_name)
+                .unwrap_infallible()
+        } else {
+            false
+        }
+    }
+
+    /// Inserts a graph into this store
+    ///
+    /// Usage example:
+    /// ```
+    /// use oxigraph::MemoryStore;
+    /// use oxigraph::model::NamedNode;
+    ///
+    /// let ex = NamedNode::new("http://example.com")?;
+    /// let store = MemoryStore::new();
+    /// store.insert_named_graph(ex.clone());
+    /// assert_eq!(store.named_graphs().count(), 1);
+    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
+    /// ```
+    pub fn insert_named_graph(&self, graph_name: impl Into<NamedOrBlankNode>) {
+        let mut this = self;
+        let graph_name = this
+            .encode_named_or_blank_node(graph_name.into().as_ref())
+            .unwrap_infallible();
+        this.insert_encoded_named_graph(graph_name)
+            .unwrap_infallible()
+    }
+
+    /// Clears a graph from this store.
     ///
     /// Usage example:
     /// ```
@@ -465,22 +533,50 @@ impl MemoryStore {
     /// let ex = NamedNode::new("http://example.com")?;
     /// let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), ex.clone());
     /// let store = MemoryStore::new();
-    /// store.insert(quad.clone());    
+    /// store.insert(quad.clone());
     /// assert_eq!(1, store.len());
     ///
-    /// store.drop_graph(&ex);
+    /// store.clear_graph(&ex);
     /// assert_eq!(0, store.len());
+    /// assert_eq!(1, store.named_graphs().count());
     /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
     /// ```
-    pub fn drop_graph<'a>(&self, graph_name: impl Into<GraphNameRef<'a>>) {
+    pub fn clear_graph<'a>(&self, graph_name: impl Into<GraphNameRef<'a>>) {
         if let Some(graph_name) = self
             .get_encoded_graph_name(graph_name.into())
             .unwrap_infallible()
         {
-            for quad in self.encoded_quads_for_pattern_inner(None, None, None, Some(graph_name)) {
-                let mut this = self;
-                this.remove_encoded(&quad).unwrap_infallible();
-            }
+            let mut this = self;
+            this.clear_encoded_graph(graph_name).unwrap_infallible()
+        }
+    }
+
+    /// Removes a graph from this store.
+    ///
+    /// Usage example:
+    /// ```
+    /// use oxigraph::MemoryStore;
+    /// use oxigraph::model::{NamedNode, Quad};
+    ///
+    /// let ex = NamedNode::new("http://example.com")?;
+    /// let quad = Quad::new(ex.clone(), ex.clone(), ex.clone(), ex.clone());
+    /// let store = MemoryStore::new();
+    /// store.insert(quad.clone());
+    /// assert_eq!(1, store.len());
+    ///
+    /// store.remove_named_graph(&ex);
+    /// assert_eq!(0, store.len());
+    /// assert_eq!(0, store.named_graphs().count());
+    /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
+    /// ```
+    pub fn remove_named_graph<'a>(&self, graph_name: impl Into<NamedOrBlankNodeRef<'a>>) {
+        if let Some(graph_name) = self
+            .get_encoded_named_or_blank_node(graph_name.into())
+            .unwrap_infallible()
+        {
+            let mut this = self;
+            this.remove_encoded_named_graph(graph_name)
+                .unwrap_infallible()
         }
     }
 
@@ -502,7 +598,7 @@ impl MemoryStore {
     /// # Result::<_,Box<dyn std::error::Error>>::Ok(())
     /// ```
     pub fn clear(&self) {
-        *self.indexes_mut() = MemoryStoreIndexes::default();
+        self.indexes_mut().clear().unwrap_infallible()
     }
 
     #[allow(clippy::expect_used)]
@@ -891,6 +987,7 @@ impl<'a> StrContainer for &'a MemoryStore {
 
 impl<'a> ReadableEncodedStore for MemoryStore {
     type QuadsIter = EncodedQuadsIter;
+    type GraphsIter = EncodedGraphsIter;
 
     fn encoded_quads_for_pattern(
         &self,
@@ -905,6 +1002,22 @@ impl<'a> ReadableEncodedStore for MemoryStore {
                 .into_iter(),
         }
     }
+
+    fn encoded_named_graphs(&self) -> Self::GraphsIter {
+        EncodedGraphsIter {
+            iter: self
+                .indexes()
+                .gosp
+                .keys()
+                .cloned()
+                .collect::<Vec<_>>()
+                .into_iter(),
+        }
+    }
+
+    fn contains_encoded_named_graph(&self, graph_name: EncodedTerm) -> Result<bool, Infallible> {
+        Ok(self.indexes().gspo.contains_key(&graph_name))
+    }
 }
 
 impl<'a> WritableEncodedStore for &'a MemoryStore {
@@ -915,6 +1028,22 @@ impl<'a> WritableEncodedStore for &'a MemoryStore {
     fn remove_encoded(&mut self, quad: &EncodedQuad) -> Result<(), Infallible> {
         self.indexes_mut().remove_encoded(quad)
     }
+
+    fn insert_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), Infallible> {
+        self.indexes_mut().insert_encoded_named_graph(graph_name)
+    }
+
+    fn clear_encoded_graph(&mut self, graph_name: EncodedTerm) -> Result<(), Infallible> {
+        self.indexes_mut().clear_encoded_graph(graph_name)
+    }
+
+    fn remove_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), Infallible> {
+        self.indexes_mut().remove_encoded_named_graph(graph_name)
+    }
+
+    fn clear(&mut self) -> Result<(), Self::Error> {
+        self.indexes_mut().clear()
+    }
 }
 
 impl StrEncodingAware for MemoryStoreIndexes {
@@ -1011,27 +1140,15 @@ impl WritableEncodedStore for MemoryStoreIndexes {
                 &quad.predicate,
             );
         } else {
-            remove_from_quad_map(
-                &mut self.gspo,
-                &quad.graph_name,
-                &quad.subject,
-                &quad.predicate,
-                &quad.object,
-            );
-            remove_from_quad_map(
-                &mut self.gpos,
-                &quad.graph_name,
-                &quad.predicate,
-                &quad.object,
-                &quad.subject,
-            );
-            remove_from_quad_map(
-                &mut self.gosp,
-                &quad.graph_name,
-                &quad.object,
-                &quad.subject,
-                &quad.predicate,
-            );
+            if let Some(spo) = self.gspo.get_mut(&quad.graph_name) {
+                remove_from_triple_map(spo, &quad.subject, &quad.predicate, &quad.object);
+            }
+            if let Some(pos) = self.gpos.get_mut(&quad.graph_name) {
+                remove_from_triple_map(pos, &quad.predicate, &quad.object, &quad.subject);
+            }
+            if let Some(osp) = self.gosp.get_mut(&quad.graph_name) {
+                remove_from_triple_map(osp, &quad.object, &quad.subject, &quad.predicate);
+            }
             remove_from_quad_map(
                 &mut self.spog,
                 &quad.subject,
@@ -1056,6 +1173,66 @@ impl WritableEncodedStore for MemoryStoreIndexes {
         }
         Ok(())
     }
+
+    fn insert_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), Infallible> {
+        self.gspo.entry(graph_name).or_default();
+        self.gpos.entry(graph_name).or_default();
+        self.gosp.entry(graph_name).or_default();
+        Ok(())
+    }
+
+    fn clear_encoded_graph(&mut self, graph_name: EncodedTerm) -> Result<(), Infallible> {
+        if graph_name.is_default_graph() {
+            self.default_spo.clear();
+            self.default_pos.clear();
+            self.default_osp.clear();
+        } else {
+            if let Some(spo) = self.gspo.get(&graph_name) {
+                for (s, po) in spo {
+                    for (p, os) in po {
+                        for o in os {
+                            remove_from_quad_map(&mut self.spog, s, p, o, &graph_name);
+                            remove_from_quad_map(&mut self.posg, p, o, s, &graph_name);
+                            remove_from_quad_map(&mut self.ospg, o, s, p, &graph_name);
+                        }
+                    }
+                }
+            }
+            if let Some(spo) = self.gspo.get_mut(&graph_name) {
+                spo.clear();
+            }
+            if let Some(pos) = self.gpos.get_mut(&graph_name) {
+                pos.clear();
+            }
+            if let Some(osp) = self.gosp.get_mut(&graph_name) {
+                osp.clear();
+            }
+        }
+        Ok(())
+    }
+
+    fn remove_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), Infallible> {
+        if let Some(spo) = self.gspo.get(&graph_name) {
+            for (s, po) in spo {
+                for (p, os) in po {
+                    for o in os {
+                        remove_from_quad_map(&mut self.spog, s, p, o, &graph_name);
+                        remove_from_quad_map(&mut self.posg, p, o, s, &graph_name);
+                        remove_from_quad_map(&mut self.ospg, o, s, p, &graph_name);
+                    }
+                }
+            }
+        }
+        self.gspo.remove(&graph_name);
+        self.gpos.remove(&graph_name);
+        self.gosp.remove(&graph_name);
+        Ok(())
+    }
+
+    fn clear(&mut self) -> Result<(), Infallible> {
+        *self = MemoryStoreIndexes::default();
+        Ok(())
+    }
 }
 
 fn insert_into_triple_map<T: Eq + Hash>(map: &mut TripleMap<T>, e1: T, e2: T, e3: T) {
@@ -1337,6 +1514,29 @@ impl Iterator for EncodedQuadsIter {
     }
 }
 
+pub(crate) struct EncodedGraphsIter {
+    iter: IntoIter<EncodedTerm>,
+}
+
+impl Iterator for EncodedGraphsIter {
+    type Item = Result<EncodedTerm, Infallible>;
+
+    fn next(&mut self) -> Option<Result<EncodedTerm, Infallible>> {
+        self.iter.next().map(Ok)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+
+    fn fold<Acc, G>(self, init: Acc, mut g: G) -> Acc
+    where
+        G: FnMut(Acc, Self::Item) -> Acc,
+    {
+        self.iter.fold(init, |acc, elt| g(acc, Ok(elt)))
+    }
+}
+
 /// An iterator returning the quads contained in a [`MemoryStore`].
 pub struct MemoryQuadIter {
     iter: IntoIter<EncodedQuad>,
@@ -1355,6 +1555,28 @@ impl Iterator for MemoryQuadIter {
     }
 }
 
+/// An iterator returning the graph names contained in a [`MemoryStore`].
+pub struct MemoryGraphNameIter {
+    iter: EncodedGraphsIter,
+    store: MemoryStore,
+}
+
+impl Iterator for MemoryGraphNameIter {
+    type Item = NamedOrBlankNode;
+
+    fn next(&mut self) -> Option<NamedOrBlankNode> {
+        Some(
+            self.store
+                .decode_named_or_blank_node(self.iter.next()?.unwrap_infallible())
+                .unwrap(),
+        )
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
 impl StrId for LargeSpur {}
 
 // Isomorphism implementation

lib/src/store/mod.rs

@@ -34,6 +34,7 @@ use std::iter::Iterator;
 
 pub(crate) trait ReadableEncodedStore: StrLookup {
     type QuadsIter: Iterator<Item = Result<EncodedQuad<Self::StrId>, Self::Error>> + 'static;
+    type GraphsIter: Iterator<Item = Result<EncodedTerm<Self::StrId>, Self::Error>> + 'static;
 
     fn encoded_quads_for_pattern(
         &self,
@@ -42,12 +43,36 @@ pub(crate) trait ReadableEncodedStore: StrLookup {
         object: Option<EncodedTerm<Self::StrId>>,
         graph_name: Option<EncodedTerm<Self::StrId>>,
     ) -> Self::QuadsIter;
+
+    fn encoded_named_graphs(&self) -> Self::GraphsIter;
+
+    fn contains_encoded_named_graph(
+        &self,
+        graph_name: EncodedTerm<Self::StrId>,
+    ) -> Result<bool, Self::Error>;
 }
 
 pub(crate) trait WritableEncodedStore: StrEncodingAware {
     fn insert_encoded(&mut self, quad: &EncodedQuad<Self::StrId>) -> Result<(), Self::Error>;
 
     fn remove_encoded(&mut self, quad: &EncodedQuad<Self::StrId>) -> Result<(), Self::Error>;
+
+    fn insert_encoded_named_graph(
+        &mut self,
+        graph_name: EncodedTerm<Self::StrId>,
+    ) -> Result<(), Self::Error>;
+
+    fn clear_encoded_graph(
+        &mut self,
+        graph_name: EncodedTerm<Self::StrId>,
+    ) -> Result<(), Self::Error>;
+
+    fn remove_encoded_named_graph(
+        &mut self,
+        graph_name: EncodedTerm<Self::StrId>,
+    ) -> Result<(), Self::Error>;
+
+    fn clear(&mut self) -> Result<(), Self::Error>;
 }
 
 pub(crate) fn load_graph<S: WritableEncodedStore + StrContainer>(

lib/src/store/rocksdb.rs

@@ -77,9 +77,11 @@ const GOSP_CF: &str = "gosp";
 const DSPO_CF: &str = "dspo";
 const DPOS_CF: &str = "dpos";
 const DOSP_CF: &str = "dosp";
+const GRAPHS_CF: &str = "graphs";
 
-const COLUMN_FAMILIES: [&str; 10] = [
+const COLUMN_FAMILIES: [&str; 11] = [
     ID2STR_CF, SPOG_CF, POSG_CF, OSPG_CF, GSPO_CF, GPOS_CF, GOSP_CF, DSPO_CF, DPOS_CF, DOSP_CF,
+    GRAPHS_CF,
 ];
 
 const MAX_TRANSACTION_SIZE: usize = 1024;
@@ -96,15 +98,33 @@ impl RocksDbStore {
             db: Arc::new(DB::open_cf(&options, path, &COLUMN_FAMILIES).map_err(map_err)?),
         };
 
-        let version = this.ensure_version()?;
-        if version != LATEST_STORAGE_VERSION {
-            return Err(invalid_data_error(format!(
-                "The RocksDB database is still using the encoding version {}, please upgrade it",
-                version
-            )));
+        let mut version = this.ensure_version()?;
+        if version == 0 {
+            // We migrate to v1
+            let mut transaction = this.auto_batch_writer();
+            for quad in this.encoded_quads_for_pattern(None, None, None, None) {
+                let quad = quad?;
+                if !quad.graph_name.is_default_graph() {
+                    transaction.insert_encoded_named_graph(quad.graph_name)?;
+                }
+            }
+            transaction.apply()?;
+            version = 1;
+            this.set_version(version)?;
+            this.flush()?;
         }
 
-        Ok(this)
+        match version {
+            _ if version < LATEST_STORAGE_VERSION => Err(invalid_data_error(format!(
+                "The RocksDB database is using the outdated encoding version {}. Automated migration is not supported, please dump the store dataset using a compatible Oxigraph version and load it again using the current version",
+                version
+            ))),
+            LATEST_STORAGE_VERSION => Ok(this),
+            _ => Err(invalid_data_error(format!(
+                "The RocksDB database is using the too recent version {}. Upgrade to the latest Oxigraph version to load this database",
+                version
+            )))
+        }
     }
 
     fn ensure_version(&self) -> Result<u64, io::Error> {
@@ -114,14 +134,25 @@ impl RocksDbStore {
                 buffer.copy_from_slice(&version);
                 u64::from_be_bytes(buffer)
             } else {
-                self.db
-                    .put("oxversion", &LATEST_STORAGE_VERSION.to_be_bytes())
-                    .map_err(map_err)?;
+                self.set_version(LATEST_STORAGE_VERSION)?;
                 LATEST_STORAGE_VERSION
             },
         )
     }
 
+    fn set_version(&self, version: u64) -> Result<(), io::Error> {
+        self.db
+            .put("oxversion", &version.to_be_bytes())
+            .map_err(map_err)
+    }
+
+    fn flush(&self) -> Result<(), io::Error> {
+        let mut options = FlushOptions::new();
+        options.set_wait(true);
+        self.db.flush_opt(&options).map_err(map_err)?;
+        Ok(())
+    }
+
     /// Executes a [SPARQL 1.1 query](https://www.w3.org/TR/sparql11-query/).
     ///
     /// See [`MemoryStore`](super::memory::MemoryStore::query()) for a usage example.
@@ -352,15 +383,68 @@ impl RocksDbStore {
         dump_dataset(self.iter(), writer, syntax)
     }
 
-    /// Removes a graph from this store.
+    /// Returns all the store named graphs
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::named_graphs()) for a usage example.
+    pub fn named_graphs(&self) -> impl Iterator<Item = Result<NamedOrBlankNode, io::Error>> {
+        let this = self.clone();
+        self.encoded_named_graphs()
+            .map(move |g| Ok(this.decode_named_or_blank_node(g?)?))
+    }
+
+    /// Checks if the store contains a given graph
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::contains_named_graph()) for a usage example.
+    pub fn contains_named_graph<'a>(
+        &self,
+        graph_name: impl Into<NamedOrBlankNodeRef<'a>>,
+    ) -> Result<bool, io::Error> {
+        if let Some(graph_name) = self.get_encoded_named_or_blank_node(graph_name.into())? {
+            self.contains_encoded_named_graph(graph_name)
+        } else {
+            Ok(false)
+        }
+    }
+
+    /// Inserts a graph into this store
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::insert_named_graph()) for a usage example.
+    pub fn insert_named_graph<'a>(
+        &self,
+        graph_name: impl Into<NamedOrBlankNodeRef<'a>>,
+    ) -> Result<(), io::Error> {
+        let mut transaction = self.auto_batch_writer();
+        let graph_name = transaction.encode_named_or_blank_node(graph_name.into())?;
+        transaction.insert_encoded_named_graph(graph_name)?;
+        transaction.apply()
+    }
+
+    /// Clears a graph from this store.
     ///
-    /// See [`MemoryStore`](super::memory::MemoryStore::drop_graph()) for a usage example.
-    pub fn drop_graph<'a>(&self, graph_name: impl Into<GraphNameRef<'a>>) -> Result<(), io::Error> {
+    /// See [`MemoryStore`](super::memory::MemoryStore::clear_graph()) for a usage example.
+    pub fn clear_graph<'a>(
+        &self,
+        graph_name: impl Into<GraphNameRef<'a>>,
+    ) -> Result<(), io::Error> {
         if let Some(graph_name) = self.get_encoded_graph_name(graph_name.into())? {
             let mut transaction = self.auto_batch_writer();
-            for quad in self.encoded_quads_for_pattern(None, None, None, Some(graph_name)) {
-                transaction.remove_encoded(&quad?)?;
-            }
+            transaction.clear_encoded_graph(graph_name)?;
+            transaction.apply()
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Removes a graph from this store.
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::remove_named_graph()) for a usage example.
+    pub fn remove_named_graph<'a>(
+        &self,
+        graph_name: impl Into<NamedOrBlankNodeRef<'a>>,
+    ) -> Result<(), io::Error> {
+        if let Some(graph_name) = self.get_encoded_named_or_blank_node(graph_name.into())? {
+            let mut transaction = self.auto_batch_writer();
+            transaction.remove_encoded_named_graph(graph_name)?;
             transaction.apply()
         } else {
             Ok(())
@@ -371,17 +455,9 @@ impl RocksDbStore {
     ///
     /// See [`MemoryStore`](super::memory::MemoryStore::clear()) for a usage example.
     pub fn clear(&self) -> Result<(), io::Error> {
-        self.clear_cf(self.id2str_cf())?;
-        self.clear_cf(self.spog_cf())?;
-        self.clear_cf(self.posg_cf())?;
-        self.clear_cf(self.ospg_cf())?;
-        self.clear_cf(self.gspo_cf())?;
-        self.clear_cf(self.gpos_cf())?;
-        self.clear_cf(self.gosp_cf())?;
-        self.clear_cf(self.dspo_cf())?;
-        self.clear_cf(self.dpos_cf())?;
-        self.clear_cf(self.dosp_cf())?;
-        Ok(())
+        let mut transaction = self.auto_batch_writer();
+        transaction.clear()?;
+        transaction.apply()
     }
 
     fn id2str_cf(&self) -> &ColumnFamily {
@@ -424,6 +500,9 @@ impl RocksDbStore {
         get_cf(&self.db, DOSP_CF)
     }
 
+    fn graphs_cf(&self) -> &ColumnFamily {
+        get_cf(&self.db, GRAPHS_CF)
+    }
     fn auto_batch_writer(&self) -> AutoBatchWriter<'_> {
         AutoBatchWriter {
             store: self,
@@ -657,48 +736,25 @@ impl RocksDbStore {
         self.inner_quads(self.dosp_cf(), prefix, QuadEncoding::DOSP)
     }
 
-    #[allow(unsafe_code)]
     fn inner_quads(
         &self,
         cf: &ColumnFamily,
         prefix: Vec<u8>,
         encoding: QuadEncoding,
     ) -> DecodingIndexIterator {
-        let mut iter = self.db.raw_iterator_cf(cf);
-        iter.seek(&prefix);
+        let mut iter = self.db_iter(cf);
+        iter.iter.seek(&prefix);
         DecodingIndexIterator {
-            iter: unsafe { StaticDBRowIterator::new(iter, self.db.clone()) }, // This is safe because the iterator belongs to DB
+            iter,
             prefix,
             encoding,
         }
     }
 
-    fn clear_cf(&self, cf: &ColumnFamily) -> Result<(), io::Error> {
-        self.db
-            .delete_range_cf(
-                cf,
-                [
-                    u8::MIN,
-                    u8::MIN,
-                    u8::MIN,
-                    u8::MIN,
-                    u8::MIN,
-                    u8::MIN,
-                    u8::MIN,
-                    u8::MIN,
-                ],
-                [
-                    u8::MAX,
-                    u8::MAX,
-                    u8::MAX,
-                    u8::MAX,
-                    u8::MAX,
-                    u8::MAX,
-                    u8::MAX,
-                    u8::MAX,
-                ],
-            )
-            .map_err(map_err)
+    #[allow(unsafe_code)]
+    fn db_iter(&self, cf: &ColumnFamily) -> StaticDBRowIterator {
+        // Valid because it's the same database so db can't be dropped before iter
+        unsafe { StaticDBRowIterator::new(self.db.raw_iterator_cf(cf), self.db.clone()) }
     }
 }
 
@@ -745,6 +801,7 @@ impl StrLookup for RocksDbStore {
 
 impl ReadableEncodedStore for RocksDbStore {
     type QuadsIter = DecodingIndexesIterator;
+    type GraphsIter = DecodingGraphIterator;
 
     fn encoded_quads_for_pattern(
         &self,
@@ -809,6 +866,20 @@ impl ReadableEncodedStore for RocksDbStore {
             },
         }
     }
+
+    fn encoded_named_graphs(&self) -> DecodingGraphIterator {
+        let mut iter = self.db_iter(self.graphs_cf());
+        iter.iter.seek_to_first();
+        DecodingGraphIterator { iter }
+    }
+
+    fn contains_encoded_named_graph(&self, graph_name: EncodedTerm) -> Result<bool, io::Error> {
+        Ok(self
+            .db
+            .get_cf(self.graphs_cf(), &encode_term(graph_name))
+            .map_err(map_err)?
+            .is_some())
+    }
 }
 
 struct AutoBatchWriter<'a> {
@@ -831,6 +902,32 @@ impl AutoBatchWriter<'_> {
         }
         Ok(())
     }
+
+    fn clear_cf(&mut self, cf: &ColumnFamily) {
+        self.batch.delete_range_cf(
+            cf,
+            [
+                u8::MIN,
+                u8::MIN,
+                u8::MIN,
+                u8::MIN,
+                u8::MIN,
+                u8::MIN,
+                u8::MIN,
+                u8::MIN,
+            ],
+            [
+                u8::MAX,
+                u8::MAX,
+                u8::MAX,
+                u8::MAX,
+                u8::MAX,
+                u8::MAX,
+                u8::MAX,
+                u8::MAX,
+            ],
+        )
+    }
 }
 
 impl StrEncodingAware for AutoBatchWriter<'_> {
@@ -885,6 +982,10 @@ impl WritableEncodedStore for AutoBatchWriter<'_> {
             write_gosp_quad(&mut self.buffer, quad);
             self.batch.put_cf(self.store.gosp_cf(), &self.buffer, &[]);
             self.buffer.clear();
+
+            write_term(&mut self.buffer, quad.graph_name);
+            self.batch.put_cf(self.store.graphs_cf(), &self.buffer, &[]);
+            self.buffer.clear();
         }
 
         self.apply_if_big()
@@ -931,6 +1032,49 @@ impl WritableEncodedStore for AutoBatchWriter<'_> {
 
         self.apply_if_big()
     }
+
+    fn insert_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        self.batch
+            .put_cf(self.store.graphs_cf(), &encode_term(graph_name), &[]);
+        self.apply_if_big()
+    }
+
+    fn clear_encoded_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        if graph_name.is_default_graph() {
+            self.clear_cf(self.store.dspo_cf());
+            self.clear_cf(self.store.dpos_cf());
+            self.clear_cf(self.store.dosp_cf());
+        } else {
+            for quad in self.store.quads_for_graph(graph_name) {
+                self.remove_encoded(&quad?)?;
+            }
+        }
+        self.apply_if_big()
+    }
+
+    fn remove_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        for quad in self.store.quads_for_graph(graph_name) {
+            self.remove_encoded(&quad?)?;
+        }
+        self.batch
+            .delete_cf(self.store.graphs_cf(), &encode_term(graph_name));
+        self.apply_if_big()
+    }
+
+    fn clear(&mut self) -> Result<(), io::Error> {
+        self.clear_cf(self.store.spog_cf());
+        self.clear_cf(self.store.posg_cf());
+        self.clear_cf(self.store.ospg_cf());
+        self.clear_cf(self.store.gspo_cf());
+        self.clear_cf(self.store.gpos_cf());
+        self.clear_cf(self.store.gosp_cf());
+        self.clear_cf(self.store.dspo_cf());
+        self.clear_cf(self.store.dpos_cf());
+        self.clear_cf(self.store.dosp_cf());
+        self.clear_cf(self.store.graphs_cf());
+        self.clear_cf(self.store.id2str_cf());
+        self.apply_if_big()
+    }
 }
 
 /// Allows inserting and deleting quads during an ACID transaction with the [`RocksDbStore`].
@@ -1093,6 +1237,10 @@ impl WritableEncodedStore for RocksDbTransaction<'_> {
             write_gosp_quad(&mut self.buffer, quad);
             self.batch.put_cf(self.store.gosp_cf(), &self.buffer, &[]);
             self.buffer.clear();
+
+            write_term(&mut self.buffer, quad.graph_name);
+            self.batch.put_cf(self.store.graphs_cf(), &self.buffer, &[]);
+            self.buffer.clear();
         }
 
         Ok(())
@@ -1139,6 +1287,33 @@ impl WritableEncodedStore for RocksDbTransaction<'_> {
 
         Ok(())
     }
+
+    fn insert_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        self.batch
+            .put_cf(self.store.graphs_cf(), &encode_term(graph_name), &[]);
+        Ok(())
+    }
+
+    fn clear_encoded_graph(&mut self, _: EncodedTerm) -> Result<(), io::Error> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "CLEAR is not implemented in RocksDB transactions",
+        ))
+    }
+
+    fn remove_encoded_named_graph(&mut self, _: EncodedTerm) -> Result<(), io::Error> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "DROP is not implemented in RocksDB transactions",
+        ))
+    }
+
+    fn clear(&mut self) -> Result<(), Self::Error> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "CLEAR ALL is not implemented in RocksDB transactions",
+        ))
+    }
 }
 
 #[allow(clippy::expect_used)]
@@ -1267,6 +1442,23 @@ impl Iterator for RocksDbQuadIter {
     }
 }
 
+pub(crate) struct DecodingGraphIterator {
+    iter: StaticDBRowIterator,
+}
+
+impl Iterator for DecodingGraphIterator {
+    type Item = Result<EncodedTerm, io::Error>;
+
+    fn next(&mut self) -> Option<Result<EncodedTerm, io::Error>> {
+        if let Some(key) = self.iter.key() {
+            let result = decode_term(key);
+            self.iter.next();
+            Some(result)
+        } else {
+            None
+        }
+    }
+}
 #[test]
 fn store() -> Result<(), io::Error> {
     use crate::model::*;

lib/src/store/sled.rs

@@ -75,6 +75,7 @@ pub struct SledStore {
     dspo: Tree,
     dpos: Tree,
     dosp: Tree,
+    graphs: Tree,
 }
 
 type EncodedTerm = crate::store::numeric_encoder::EncodedTerm<StrHash>;
@@ -107,17 +108,35 @@ impl SledStore {
             dspo: db.open_tree("dspo")?,
             dpos: db.open_tree("dpos")?,
             dosp: db.open_tree("dosp")?,
+            graphs: db.open_tree("graphs")?,
         };
 
-        let version = this.ensure_version()?;
-        if version != LATEST_STORAGE_VERSION {
-            return Err(invalid_data_error(format!(
-                "The Sled database is still using the encoding version {}, please upgrade it",
-                version
-            )));
+        let mut version = this.ensure_version()?;
+        if version == 0 {
+            // We migrate to v1
+            for quad in this.encoded_quads_for_pattern(None, None, None, None) {
+                let mut this_mut = &this;
+                let quad = quad?;
+                if !quad.graph_name.is_default_graph() {
+                    this_mut.insert_encoded_named_graph(quad.graph_name)?;
+                }
+            }
+            version = 1;
+            this.set_version(version)?;
+            this.graphs.flush()?;
         }
 
-        Ok(this)
+        match version {
+            _ if version < LATEST_STORAGE_VERSION => Err(invalid_data_error(format!(
+                "The Sled database is using the outdated encoding version {}. Automated migration is not supported, please dump the store dataset using a compatible Oxigraph version and load it again using the current version",
+                version
+            ))),
+            LATEST_STORAGE_VERSION => Ok(this),
+            _ => Err(invalid_data_error(format!(
+                "The Sled database is using the too recent version {}. Upgrade to the latest Oxigraph version to load this database",
+                version
+            )))
+        }
     }
 
     fn ensure_version(&self) -> Result<u64, io::Error> {
@@ -126,12 +145,16 @@ impl SledStore {
             buffer.copy_from_slice(&version);
             u64::from_be_bytes(buffer)
         } else {
-            self.default
-                .insert("oxversion", &LATEST_STORAGE_VERSION.to_be_bytes())?;
+            self.set_version(LATEST_STORAGE_VERSION)?;
             LATEST_STORAGE_VERSION
         })
     }
 
+    fn set_version(&self, version: u64) -> Result<(), io::Error> {
+        self.default.insert("oxversion", &version.to_be_bytes())?;
+        Ok(())
+    }
+
     /// Executes a [SPARQL 1.1 query](https://www.w3.org/TR/sparql11-query/).
     ///
     /// See [`MemoryStore`](super::memory::MemoryStore::query()) for a usage example.
@@ -268,9 +291,10 @@ impl SledStore {
             &self.dspo,
             &self.dpos,
             &self.dosp,
+            &self.graphs,
         )
             .transaction(
-                move |(id2str, spog, posg, ospg, gspo, gpos, gosp, dspo, dpos, dosp)| {
+                move |(id2str, spog, posg, ospg, gspo, gpos, gosp, dspo, dpos, dosp, graphs)| {
                     Ok(f(SledTransaction {
                         id2str,
                         spog,
@@ -282,6 +306,7 @@ impl SledStore {
                         dspo,
                         dpos,
                         dosp,
+                        graphs,
                     })?)
                 },
             )?)
@@ -385,34 +410,78 @@ impl SledStore {
         dump_dataset(self.iter(), writer, format)
     }
 
-    /// Removes a graph from this store.
+    /// Returns all the store named graphs
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::named_graphs()) for a usage example.
+    pub fn named_graphs(&self) -> SledGraphNameIter {
+        SledGraphNameIter {
+            iter: self.encoded_named_graphs(),
+            store: self.clone(),
+        }
+    }
+
+    /// Checks if the store contains a given graph
     ///
-    /// See [`MemoryStore`](super::memory::MemoryStore::drop_graph()) for a usage example.
-    pub fn drop_graph<'a>(&self, graph_name: impl Into<GraphNameRef<'a>>) -> Result<(), io::Error> {
+    /// See [`MemoryStore`](super::memory::MemoryStore::contains_named_graph()) for a usage example.
+    pub fn contains_named_graph<'a>(
+        &self,
+        graph_name: impl Into<NamedOrBlankNodeRef<'a>>,
+    ) -> Result<bool, io::Error> {
+        if let Some(graph_name) = self.get_encoded_named_or_blank_node(graph_name.into())? {
+            self.contains_encoded_named_graph(graph_name)
+        } else {
+            Ok(false)
+        }
+    }
+
+    /// Inserts a graph into this store
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::insert_named_graph()) for a usage example.
+    pub fn insert_named_graph<'a>(
+        &self,
+        graph_name: impl Into<NamedOrBlankNodeRef<'a>>,
+    ) -> Result<(), io::Error> {
+        let mut this = self;
+        let graph_name = this.encode_named_or_blank_node(graph_name.into())?;
+        this.insert_encoded_named_graph(graph_name)
+    }
+
+    /// Clears a graph from this store.
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::clear_graph()) for a usage example.
+    pub fn clear_graph<'a>(
+        &self,
+        graph_name: impl Into<GraphNameRef<'a>>,
+    ) -> Result<(), io::Error> {
         if let Some(graph_name) = self.get_encoded_graph_name(graph_name.into())? {
-            for quad in self.encoded_quads_for_pattern(None, None, None, Some(graph_name)) {
-                let mut this = self;
-                this.remove_encoded(&quad?)?;
-            }
+            let mut this = self;
+            this.clear_encoded_graph(graph_name)
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Removes a graph from this store.
+    ///
+    /// See [`MemoryStore`](super::memory::MemoryStore::remove_named_graph()) for a usage example.
+    pub fn remove_named_graph<'a>(
+        &self,
+        graph_name: impl Into<NamedOrBlankNodeRef<'a>>,
+    ) -> Result<(), io::Error> {
+        if let Some(graph_name) = self.get_encoded_named_or_blank_node(graph_name.into())? {
+            let mut this = self;
+            this.remove_encoded_named_graph(graph_name)
+        } else {
+            Ok(())
         }
-        Ok(())
     }
 
     /// Clears the store.
     ///
     /// See [`MemoryStore`](super::memory::MemoryStore::clear()) for a usage example.
     pub fn clear(&self) -> Result<(), io::Error> {
-        self.dspo.clear()?;
-        self.dpos.clear()?;
-        self.dosp.clear()?;
-        self.gspo.clear()?;
-        self.gpos.clear()?;
-        self.gosp.clear()?;
-        self.spog.clear()?;
-        self.posg.clear()?;
-        self.ospg.clear()?;
-        self.id2str.clear()?;
-        Ok(())
+        let mut this = self;
+        (&mut this).clear()
     }
 
     fn contains_encoded(&self, quad: &EncodedQuad) -> Result<bool, io::Error> {
@@ -679,6 +748,7 @@ impl StrLookup for SledStore {
 
 impl ReadableEncodedStore for SledStore {
     type QuadsIter = DecodingQuadsIterator;
+    type GraphsIter = DecodingGraphIterator;
 
     fn encoded_quads_for_pattern(
         &self,
@@ -742,6 +812,16 @@ impl ReadableEncodedStore for SledStore {
             },
         }
     }
+
+    fn encoded_named_graphs(&self) -> DecodingGraphIterator {
+        DecodingGraphIterator {
+            iter: self.graphs.iter(),
+        }
+    }
+
+    fn contains_encoded_named_graph(&self, graph_name: EncodedTerm) -> Result<bool, io::Error> {
+        Ok(self.graphs.contains_key(&encode_term(graph_name))?)
+    }
 }
 
 impl<'a> StrContainer for &'a SledStore {
@@ -792,6 +872,10 @@ impl<'a> WritableEncodedStore for &'a SledStore {
             write_gosp_quad(&mut buffer, quad);
             self.gosp.insert(buffer.as_slice(), &[])?;
             buffer.clear();
+
+            write_term(&mut buffer, quad.graph_name);
+            self.graphs.insert(&buffer, &[])?;
+            buffer.clear();
         }
 
         Ok(())
@@ -840,6 +924,47 @@ impl<'a> WritableEncodedStore for &'a SledStore {
 
         Ok(())
     }
+
+    fn insert_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        self.graphs.insert(&encode_term(graph_name), &[])?;
+        Ok(())
+    }
+
+    fn clear_encoded_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        if graph_name.is_default_graph() {
+            self.dspo.clear()?;
+            self.dpos.clear()?;
+            self.dosp.clear()?;
+        } else {
+            for quad in self.quads_for_graph(graph_name) {
+                self.remove_encoded(&quad?)?;
+            }
+        }
+        Ok(())
+    }
+
+    fn remove_encoded_named_graph(&mut self, graph_name: EncodedTerm) -> Result<(), io::Error> {
+        for quad in self.quads_for_graph(graph_name) {
+            self.remove_encoded(&quad?)?;
+        }
+        self.graphs.remove(&encode_term(graph_name))?;
+        Ok(())
+    }
+
+    fn clear(&mut self) -> Result<(), io::Error> {
+        self.dspo.clear()?;
+        self.dpos.clear()?;
+        self.dosp.clear()?;
+        self.gspo.clear()?;
+        self.gpos.clear()?;
+        self.gosp.clear()?;
+        self.spog.clear()?;
+        self.posg.clear()?;
+        self.ospg.clear()?;
+        self.graphs.clear()?;
+        self.id2str.clear()?;
+        Ok(())
+    }
 }
 
 /// Allows inserting and deleting quads during an ACID transaction with the [`SledStore`].
@@ -854,6 +979,7 @@ pub struct SledTransaction<'a> {
     dspo: &'a TransactionalTree,
     dpos: &'a TransactionalTree,
     dosp: &'a TransactionalTree,
+    graphs: &'a TransactionalTree,
 }
 
 impl SledTransaction<'_> {
@@ -1058,6 +1184,41 @@ impl<'a> WritableEncodedStore for &'a SledTransaction<'a> {
 
         Ok(())
     }
+
+    fn insert_encoded_named_graph(
+        &mut self,
+        graph_name: EncodedTerm,
+    ) -> Result<(), SledUnabortableTransactionError> {
+        self.graphs.insert(encode_term(graph_name), &[])?;
+        Ok(())
+    }
+
+    fn clear_encoded_graph(
+        &mut self,
+        _: EncodedTerm,
+    ) -> Result<(), SledUnabortableTransactionError> {
+        Err(SledUnabortableTransactionError::Storage(io::Error::new(
+            io::ErrorKind::Other,
+            "CLEAR is not implemented in Sled transactions",
+        )))
+    }
+
+    fn remove_encoded_named_graph(
+        &mut self,
+        _: EncodedTerm,
+    ) -> Result<(), SledUnabortableTransactionError> {
+        Err(SledUnabortableTransactionError::Storage(io::Error::new(
+            io::ErrorKind::Other,
+            "DROP is not implemented in Sled transactions",
+        )))
+    }
+
+    fn clear(&mut self) -> Result<(), SledUnabortableTransactionError> {
+        Err(SledUnabortableTransactionError::Storage(io::Error::new(
+            io::ErrorKind::Other,
+            "CLEAR ALL is not implemented in Sled transactions",
+        )))
+    }
 }
 
 /// Error returned by a Sled transaction
@@ -1263,6 +1424,21 @@ impl Iterator for DecodingQuadIterator {
     }
 }
 
+pub(crate) struct DecodingGraphIterator {
+    iter: Iter,
+}
+
+impl Iterator for DecodingGraphIterator {
+    type Item = Result<EncodedTerm, io::Error>;
+
+    fn next(&mut self) -> Option<Result<EncodedTerm, io::Error>> {
+        Some(match self.iter.next()? {
+            Ok((encoded, _)) => decode_term(&encoded),
+            Err(error) => Err(error.into()),
+        })
+    }
+}
+
 /// An iterator returning the quads contained in a [`SledStore`].
 pub struct SledQuadIter {
     inner: QuadIterInner,
@@ -1292,6 +1468,28 @@ impl Iterator for SledQuadIter {
     }
 }
 
+/// An iterator returning the graph names contained in a [`SledStore`].
+pub struct SledGraphNameIter {
+    iter: DecodingGraphIterator,
+    store: SledStore,
+}
+
+impl Iterator for SledGraphNameIter {
+    type Item = Result<NamedOrBlankNode, io::Error>;
+
+    fn next(&mut self) -> Option<Result<NamedOrBlankNode, io::Error>> {
+        Some(
+            self.iter
+                .next()?
+                .and_then(|graph_name| Ok(self.store.decode_named_or_blank_node(graph_name)?)),
+        )
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
 #[test]
 fn store() -> Result<(), io::Error> {
     use crate::model::*;

lib/tests/rocksdb_store.rs

@@ -1,12 +1,11 @@
-#![cfg(features = "rocksdb")]
-
 use oxigraph::model::vocab::{rdf, xsd};
 use oxigraph::model::*;
 use oxigraph::RocksDbStore;
 use std::io;
 use std::process::Command;
 
-fn quads(graph_name: GraphNameRef<'static>) -> Vec<QuadRef<'static>> {
+fn quads(graph_name: impl Into<GraphNameRef<'static>>) -> Vec<QuadRef<'static>> {
+    let graph_name = graph_name.into();
     let paris = NamedNodeRef::new_unchecked("http://www.wikidata.org/entity/Q90");
     let france = NamedNodeRef::new_unchecked("http://www.wikidata.org/entity/Q142");
     let city = NamedNodeRef::new_unchecked("http://schema.org/City");
@@ -65,18 +64,26 @@ fn test_backward_compatibility() -> io::Result<()> {
         for q in quads(GraphNameRef::DefaultGraph) {
             assert!(store.contains(q)?);
         }
-        for q in quads(
-            NamedNodeRef::new_unchecked("http://www.wikidata.org/wiki/Special:EntityData/Q90")
-                .into(),
-        ) {
+        let graph_name =
+            NamedNodeRef::new_unchecked("http://www.wikidata.org/wiki/Special:EntityData/Q90");
+        for q in quads(graph_name) {
             assert!(store.contains(q)?);
         }
+        assert!(store.contains_named_graph(graph_name)?);
+        assert_eq!(
+            vec![NamedOrBlankNode::from(graph_name)],
+            store.named_graphs().collect::<io::Result<Vec<_>>>()?
+        );
     };
     reset_dir("tests/rockdb_bc_data")?;
     Ok(())
 }
 
 fn reset_dir(dir: &str) -> io::Result<()> {
+    assert!(Command::new("git")
+        .args(&["clean", "-fX", dir])
+        .status()?
+        .success());
     assert!(Command::new("git")
         .args(&["checkout", "HEAD", "--", dir])
         .status()?

lib/tests/sled_store.rs

@@ -1,5 +1,3 @@
-#![cfg(features = "sled")]
-
 use oxigraph::io::{DatasetFormat, GraphFormat};
 use oxigraph::model::vocab::{rdf, xsd};
 use oxigraph::model::*;
@@ -24,7 +22,8 @@ wd:Q90 a schema:City ;
 "#;
 const NUMBER_OF_TRIPLES: usize = 8;
 
-fn quads(graph_name: GraphNameRef<'static>) -> Vec<QuadRef<'static>> {
+fn quads(graph_name: impl Into<GraphNameRef<'static>>) -> Vec<QuadRef<'static>> {
+    let graph_name = graph_name.into();
     let paris = NamedNodeRef::new_unchecked("http://www.wikidata.org/entity/Q90");
     let france = NamedNodeRef::new_unchecked("http://www.wikidata.org/entity/Q142");
     let city = NamedNodeRef::new_unchecked("http://schema.org/City");
@@ -161,18 +160,26 @@ fn test_backward_compatibility() -> io::Result<()> {
         for q in quads(GraphNameRef::DefaultGraph) {
             assert!(store.contains(q)?);
         }
-        for q in quads(
-            NamedNodeRef::new_unchecked("http://www.wikidata.org/wiki/Special:EntityData/Q90")
-                .into(),
-        ) {
+        let graph_name =
+            NamedNodeRef::new_unchecked("http://www.wikidata.org/wiki/Special:EntityData/Q90");
+        for q in quads(graph_name) {
             assert!(store.contains(q)?);
         }
+        assert!(store.contains_named_graph(graph_name)?);
+        assert_eq!(
+            vec![NamedOrBlankNode::from(graph_name)],
+            store.named_graphs().collect::<io::Result<Vec<_>>>()?
+        );
     };
     reset_dir("tests/sled_bc_data")?;
     Ok(())
 }
 
 fn reset_dir(dir: &str) -> io::Result<()> {
+    assert!(Command::new("git")
+        .args(&["clean", "-fX", dir])
+        .status()?
+        .success());
     assert!(Command::new("git")
         .args(&["checkout", "HEAD", "--", dir])
         .status()?

python/src/memory_store.rs

@@ -3,6 +3,7 @@ use crate::model::*;
 use crate::sparql::*;
 use crate::store_utils::*;
 use oxigraph::io::{DatasetFormat, GraphFormat};
+use oxigraph::model::GraphNameRef;
 use oxigraph::store::memory::*;
 use pyo3::basic::CompareOp;
 use pyo3::exceptions::{PyNotImplementedError, PyValueError};
@@ -333,6 +334,63 @@ impl PyMemoryStore {
             )))
         }
     }
+
+    /// Returns an iterator over all the store named graphs
+    ///
+    /// >>> store = MemoryStore()
+    /// >>> store.add(Quad(NamedNode('http://example.com'), NamedNode('http://example.com/p'), Literal('1'), NamedNode('http://example.com/g')))
+    /// >>> list(store.named_graphs())
+    /// [<NamedNode value=http://example.com/g>]
+    #[text_signature = "($self)"]
+    fn named_graphs(&self) -> GraphNameIter {
+        GraphNameIter {
+            inner: self.inner.named_graphs(),
+        }
+    }
+
+    /// Adds a named graph to the store
+    ///
+    /// :param graph_name: the quad to add
+    /// :type graph_name: NamedNode or BlankNode
+    ///
+    /// >>> store = MemoryStore()
+    /// >>> store.add_graph(NamedNode('http://example.com/g'))
+    /// >>> list(store.named_graphs())
+    /// [<NamedNode value=http://example.com/g>]
+    #[text_signature = "($self, graph_name)"]
+    fn add_graph(&self, graph_name: PyGraphName) {
+        match graph_name {
+            PyGraphName::DefaultGraph(_) => (),
+            PyGraphName::NamedNode(graph_name) => self.inner.insert_named_graph(graph_name),
+            PyGraphName::BlankNode(graph_name) => self.inner.insert_named_graph(graph_name),
+        }
+    }
+
+    /// Removes a graph from the store
+    ///
+    /// The default graph will not be remove but just cleared.
+    ///
+    /// :param graph_name: the quad to add
+    /// :type graph_name: NamedNode or BlankNode or DefaultGraph
+    ///
+    /// >>> store = MemoryStore()
+    /// >>> quad = Quad(NamedNode('http://example.com'), NamedNode('http://example.com/p'), Literal('1'), NamedNode('http://example.com/g'))
+    /// >>> store.remove_graph(NamedNode('http://example.com/g'))
+    /// >>> list(store)
+    /// []
+    #[text_signature = "($self, graph_name)"]
+    fn remove_graph(&self, graph_name: &PyAny) -> PyResult<()> {
+        match PyGraphNameRef::try_from(graph_name)? {
+            PyGraphNameRef::DefaultGraph => self.inner.clear_graph(GraphNameRef::DefaultGraph),
+            PyGraphNameRef::NamedNode(graph_name) => self
+                .inner
+                .remove_named_graph(&PyNamedOrBlankNodeRef::NamedNode(graph_name)),
+            PyGraphNameRef::BlankNode(graph_name) => self
+                .inner
+                .remove_named_graph(&PyNamedOrBlankNodeRef::BlankNode(graph_name)),
+        }
+        Ok(())
+    }
 }
 
 #[pyproto]
@@ -392,3 +450,19 @@ impl PyIterProtocol for QuadIter {
         slf.inner.next().map(|q| q.into())
     }
 }
+
+#[pyclass(unsendable, module = "oxigraph")]
+pub struct GraphNameIter {
+    inner: MemoryGraphNameIter,
+}
+
+#[pyproto]
+impl PyIterProtocol for GraphNameIter {
+    fn __iter__(slf: PyRefMut<Self>) -> Py<Self> {
+        slf.into()
+    }
+
+    fn __next__(mut slf: PyRefMut<Self>) -> Option<PyNamedOrBlankNode> {
+        slf.inner.next().map(|q| q.into())
+    }
+}

python/src/sled_store.rs

@@ -3,6 +3,7 @@ use crate::model::*;
 use crate::sparql::*;
 use crate::store_utils::*;
 use oxigraph::io::{DatasetFormat, GraphFormat};
+use oxigraph::model::GraphNameRef;
 use oxigraph::store::sled::*;
 use pyo3::exceptions::PyValueError;
 use pyo3::prelude::{
@@ -351,6 +352,68 @@ impl PySledStore {
             )))
         }
     }
+
+    /// Returns an iterator over all the store named graphs
+    ///
+    /// >>> store = MemoryStore()
+    /// >>> store.add(Quad(NamedNode('http://example.com'), NamedNode('http://example.com/p'), Literal('1'), NamedNode('http://example.com/g')))
+    /// >>> list(store.named_graphs())
+    /// [<NamedNode value=http://example.com/g>]
+    #[text_signature = "($self)"]
+    fn named_graphs(&self) -> GraphNameIter {
+        GraphNameIter {
+            inner: self.inner.named_graphs(),
+        }
+    }
+
+    /// Adds a named graph to the store
+    ///
+    /// :param graph_name: the quad to add
+    /// :type graph_name: NamedNode or BlankNode
+    ///
+    /// >>> store = MemoryStore()
+    /// >>> store.add_graph(NamedNode('http://example.com/g'))
+    /// >>> list(store.named_graphs())
+    /// [<NamedNode value=http://example.com/g>]
+    #[text_signature = "($self, graph_name)"]
+    fn add_graph(&self, graph_name: &PyAny) -> PyResult<()> {
+        match PyGraphNameRef::try_from(graph_name)? {
+            PyGraphNameRef::DefaultGraph => Ok(()),
+            PyGraphNameRef::NamedNode(graph_name) => self
+                .inner
+                .insert_named_graph(&PyNamedOrBlankNodeRef::NamedNode(graph_name)),
+            PyGraphNameRef::BlankNode(graph_name) => self
+                .inner
+                .insert_named_graph(&PyNamedOrBlankNodeRef::BlankNode(graph_name)),
+        }
+        .map_err(map_io_err)
+    }
+
+    /// Removes a graph from the store
+    ///
+    /// The default graph will not be remove but just cleared.
+    ///
+    /// :param graph_name: the quad to add
+    /// :type graph_name: NamedNode or BlankNode or DefaultGraph
+    ///
+    /// >>> store = MemoryStore()
+    /// >>> quad = Quad(NamedNode('http://example.com'), NamedNode('http://example.com/p'), Literal('1'), NamedNode('http://example.com/g'))
+    /// >>> store.remove_graph(NamedNode('http://example.com/g'))
+    /// >>> list(store)
+    /// []
+    #[text_signature = "($self, graph_name)"]
+    fn remove_graph(&self, graph_name: &PyAny) -> PyResult<()> {
+        match PyGraphNameRef::try_from(graph_name)? {
+            PyGraphNameRef::DefaultGraph => self.inner.clear_graph(GraphNameRef::DefaultGraph),
+            PyGraphNameRef::NamedNode(graph_name) => self
+                .inner
+                .remove_named_graph(&PyNamedOrBlankNodeRef::NamedNode(graph_name)),
+            PyGraphNameRef::BlankNode(graph_name) => self
+                .inner
+                .remove_named_graph(&PyNamedOrBlankNodeRef::BlankNode(graph_name)),
+        }
+        .map_err(map_io_err)
+    }
 }
 
 #[pyproto]
@@ -402,3 +465,22 @@ impl PyIterProtocol for QuadIter {
             .transpose()
     }
 }
+
+#[pyclass(unsendable, module = "oxigraph")]
+pub struct GraphNameIter {
+    inner: SledGraphNameIter,
+}
+
+#[pyproto]
+impl PyIterProtocol for GraphNameIter {
+    fn __iter__(slf: PyRefMut<Self>) -> Py<Self> {
+        slf.into()
+    }
+
+    fn __next__(mut slf: PyRefMut<Self>) -> PyResult<Option<PyNamedOrBlankNode>> {
+        slf.inner
+            .next()
+            .map(|q| Ok(q.map_err(map_io_err)?.into()))
+            .transpose()
+    }
+}

python/tests/test_store.py

@@ -244,6 +244,20 @@ class TestAbstractStore(unittest.TestCase, ABC):
             store.add(Quad(triple.object, triple.predicate, triple.subject))
         self.assertEqual(len(store), 4)
 
+    def test_add_graph(self):
+        store = self.store()
+        store.add_graph(graph)
+        self.assertEqual(list(store.named_graphs()), [graph])
+
+    def test_remove_graph(self):
+        store = self.store()
+        store.add(Quad(foo, bar, baz, graph))
+        store.add_graph(NamedNode("http://graph2"))
+        store.remove_graph(graph)
+        store.remove_graph(NamedNode("http://graph2"))
+        self.assertEqual(list(store.named_graphs()), [])
+        self.assertEqual(list(store), [])
+
 
 class TestMemoryStore(TestAbstractStore):
     def store(self):