Adds method to get the size of a Graph or a Dataset

Cargo.toml

@@ -20,6 +20,7 @@ lazy_static = "1"
 rocksdb = "0.10"
 url = "1"
 uuid = { version = "0.6", features = ["v4"] }
+bzip2 = "0.3"
 byteorder = "1"
 
 [build-dependencies]

src/store/mod.rs

@@ -57,6 +57,10 @@ pub trait Graph {
     fn insert(&self, triple: &Triple) -> Result<()>;
 
     fn remove(&self, triple: &Triple) -> Result<()>;
+
+    fn len(&self) -> Result<usize>;
+
+    fn is_empty(&self) -> Result<bool>;
 }
 
 pub trait NamedGraph: Graph {
@@ -128,4 +132,8 @@ pub trait Dataset {
     fn insert(&self, quad: &Quad) -> Result<()>;
 
     fn remove(&self, quad: &Quad) -> Result<()>;
+
+    fn len(&self) -> Result<usize>;
+
+    fn is_empty(&self) -> Result<bool>;
 }

src/store/store.rs

@@ -266,6 +266,14 @@ impl<S: EncodedQuadsStore> Dataset for StoreDataset<S> {
     fn remove(&self, quad: &Quad) -> Result<()> {
         self.store.remove(&self.store.encoder().encode_quad(quad)?)
     }
+
+    fn len(&self) -> Result<usize> {
+        Ok(self.store.quads()?.count())
+    }
+
+    fn is_empty(&self) -> Result<bool> {
+        Ok(self.store.quads()?.any(|_| true))
+    }
 }
 
 pub struct StoreNamedGraph<S: EncodedQuadsStore> {
@@ -403,6 +411,17 @@ impl<S: EncodedQuadsStore> Graph for StoreNamedGraph<S> {
                 .encode_triple_in_graph(triple, self.encoded_name.clone())?,
         )
     }
+
+    fn len(&self) -> Result<usize> {
+        Ok(self.store.quads_for_graph(&self.encoded_name)?.count())
+    }
+
+    fn is_empty(&self) -> Result<bool> {
+        Ok(self
+            .store
+            .quads_for_graph(&self.encoded_name)?
+            .any(|_| true))
+    }
 }
 
 impl<S: EncodedQuadsStore> NamedGraph for StoreNamedGraph<S> {
@@ -530,6 +549,14 @@ impl<S: EncodedQuadsStore> Graph for StoreDefaultGraph<S> {
         self.store
             .remove(&self.store.encoder().encode_triple_in_graph(triple, None)?)
     }
+
+    fn len(&self) -> Result<usize> {
+        Ok(self.store.quads_for_graph(&None)?.count())
+    }
+
+    fn is_empty(&self) -> Result<bool> {
+        Ok(self.store.quads_for_graph(&None)?.any(|_| true))
+    }
 }
 
 pub struct StoreUnionGraph<S: EncodedQuadsStore> {
@@ -650,6 +677,14 @@ impl<S: EncodedQuadsStore> Graph for StoreUnionGraph<S> {
     fn remove(&self, triple: &Triple) -> Result<()> {
         unimplemented!()
     }
+
+    fn len(&self) -> Result<usize> {
+        Ok(self.store.quads()?.count())
+    }
+
+    fn is_empty(&self) -> Result<bool> {
+        Ok(self.store.quads()?.any(|_| true))
+    }
 }
 
 pub struct DelegatingBytesStore<'a, S: 'a + BytesStore + Sized>(&'a S);