Adds basic RocksDB store

.travis.yml

@@ -7,4 +7,8 @@ matrix:
   allow_failures:
     - rust: nightly
   fast_finish: true
-cache: cargo
+cache: cargo
+addons:
+  apt:
+    packages:
+      - clang

Cargo.toml

@@ -15,8 +15,10 @@ build = "build.rs"
 travis-ci = { repository = "Tpt/rudf" }
 
 [dependencies]
+error-chain = "0.12"
 lazy_static = "1.0"
-url = "1.7"
+rocksdb = "0.10"
+url = "1"
 uuid = { version = "0.6", features = ["v4"] }
 
 [build-dependencies]

src/errors.rs

@@ -0,0 +1,8 @@
+error_chain! {
+    foreign_links {
+        Url(::url::ParseError);
+        Uuid(::uuid::ParseError);
+        RocksDB(::rocksdb::Error);
+        Utf8(::std::str::Utf8Error);
+    }
+}

src/lib.rs

@@ -1,8 +1,12 @@
 #[macro_use]
+extern crate error_chain;
+#[macro_use]
 extern crate lazy_static;
+extern crate rocksdb;
 extern crate url;
 extern crate uuid;
 
+pub mod errors;
 pub mod model;
 pub mod rio;
 pub mod sparql;

src/model/blank_node.rs

@@ -28,3 +28,9 @@ impl Default for BlankNode {
         BlankNode { id: Uuid::new_v4() }
     }
 }
+
+impl From<Uuid> for BlankNode {
+    fn from(id: Uuid) -> Self {
+        Self { id }
+    }
+}

src/store/mod.rs

@@ -1,2 +1,4 @@
 pub mod isomorphism;
 pub mod memory;
+mod numeric_encoder;
+pub mod rocksdb;

src/store/numeric_encoder.rs

@@ -0,0 +1,386 @@
+use errors::*;
+use model::*;
+use std::ops::Deref;
+use std::str;
+use std::str::FromStr;
+use url::Url;
+use uuid::Uuid;
+
+pub const STRING_KEY_SIZE: usize = 8;
+
+pub trait BytesStore {
+    type BytesOutput: Deref<Target = [u8]>;
+
+    fn put(&self, value: &[u8], id_buffer: &mut [u8]) -> Result<()>;
+    fn get(&self, id: &[u8]) -> Result<Option<Self::BytesOutput>>;
+}
+
+const TYPE_KEY_SIZE: usize = 1;
+const TYPE_NAMED_NODE_ID: u8 = 1;
+const TYPE_BLANK_NODE_ID: u8 = 2;
+const TYPE_LANG_STRING_LITERAL_ID: u8 = 3;
+const TYPE_TYPED_LITERAL_ID: u8 = 4;
+pub const TERM_ENCODING_SIZE: usize = TYPE_KEY_SIZE + 2 * STRING_KEY_SIZE;
+const EMPTY_TERM: [u8; TERM_ENCODING_SIZE] = [0 as u8; TERM_ENCODING_SIZE];
+
+#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
+pub struct EncodedTerm([u8; TERM_ENCODING_SIZE]);
+
+impl EncodedTerm {
+    pub fn new_from_buffer(buffer: &[u8]) -> Result<Self> {
+        if buffer.len() != TERM_ENCODING_SIZE {
+            return Err("the term buffer has not the correct length".into());
+        }
+        let mut buf = [0 as u8; TERM_ENCODING_SIZE];
+        buf.copy_from_slice(buffer);
+        return Ok(EncodedTerm(buf));
+    }
+}
+
+impl AsRef<[u8]> for EncodedTerm {
+    fn as_ref(&self) -> &[u8] {
+        &self.0[..]
+    }
+}
+
+#[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
+pub struct EncodedQuad {
+    pub subject: EncodedTerm,
+    pub predicate: EncodedTerm,
+    pub object: EncodedTerm,
+    pub graph_name: EncodedTerm,
+}
+
+impl EncodedQuad {
+    pub fn new_from_spog_buffer(buffer: &[u8]) -> Result<Self> {
+        if buffer.len() != 4 * TERM_ENCODING_SIZE {
+            return Err("the spog buffer has not the correct length".into());
+        }
+        Ok(Self {
+            subject: EncodedTerm::new_from_buffer(&buffer[0..TERM_ENCODING_SIZE])?,
+            predicate: EncodedTerm::new_from_buffer(
+                &buffer[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE],
+            )?,
+            object: EncodedTerm::new_from_buffer(
+                &buffer[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE],
+            )?,
+            graph_name: EncodedTerm::new_from_buffer(
+                &buffer[3 * TERM_ENCODING_SIZE..4 * TERM_ENCODING_SIZE],
+            )?,
+        })
+    }
+
+    pub fn new_from_posg_buffer(buffer: &[u8]) -> Result<Self> {
+        if buffer.len() != 4 * TERM_ENCODING_SIZE {
+            return Err("the posg buffer has not the correct length".into());
+        }
+        Ok(Self {
+            subject: EncodedTerm::new_from_buffer(
+                &buffer[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE],
+            )?,
+            predicate: EncodedTerm::new_from_buffer(&buffer[0..TERM_ENCODING_SIZE])?,
+            object: EncodedTerm::new_from_buffer(
+                &buffer[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE],
+            )?,
+            graph_name: EncodedTerm::new_from_buffer(
+                &buffer[3 * TERM_ENCODING_SIZE..4 * TERM_ENCODING_SIZE],
+            )?,
+        })
+    }
+
+    pub fn new_from_ospg_buffer(buffer: &[u8]) -> Result<Self> {
+        if buffer.len() != 4 * TERM_ENCODING_SIZE {
+            return Err("the ospg buffer has not the correct length".into());
+        }
+        Ok(Self {
+            subject: EncodedTerm::new_from_buffer(
+                &buffer[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE],
+            )?,
+            predicate: EncodedTerm::new_from_buffer(
+                &buffer[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE],
+            )?,
+            object: EncodedTerm::new_from_buffer(&buffer[0..TERM_ENCODING_SIZE])?,
+            graph_name: EncodedTerm::new_from_buffer(
+                &buffer[3 * TERM_ENCODING_SIZE..4 * TERM_ENCODING_SIZE],
+            )?,
+        })
+    }
+
+    pub fn spog(&self) -> [u8; 4 * TERM_ENCODING_SIZE] {
+        let mut spog = [0 as u8; 4 * TERM_ENCODING_SIZE];
+        spog[0..TERM_ENCODING_SIZE].copy_from_slice(self.subject.as_ref());
+        spog[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE].copy_from_slice(self.predicate.as_ref());
+        spog[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE].copy_from_slice(self.object.as_ref());
+        spog[3 * TERM_ENCODING_SIZE..4 * TERM_ENCODING_SIZE]
+            .copy_from_slice(self.graph_name.as_ref());
+        spog
+    }
+
+    pub fn posg(&self) -> [u8; 4 * TERM_ENCODING_SIZE] {
+        let mut posg = [0 as u8; 4 * TERM_ENCODING_SIZE];
+        posg[0..TERM_ENCODING_SIZE].copy_from_slice(self.predicate.as_ref());
+        posg[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE].copy_from_slice(self.object.as_ref());
+        posg[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE].copy_from_slice(self.subject.as_ref());
+        posg[3 * TERM_ENCODING_SIZE..4 * TERM_ENCODING_SIZE]
+            .copy_from_slice(self.graph_name.as_ref());
+        posg
+    }
+
+    pub fn ospg(&self) -> [u8; 4 * TERM_ENCODING_SIZE] {
+        let mut ospg = [0 as u8; 4 * TERM_ENCODING_SIZE];
+        ospg[0..TERM_ENCODING_SIZE].copy_from_slice(self.object.as_ref());
+        ospg[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE].copy_from_slice(self.subject.as_ref());
+        ospg[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE]
+            .copy_from_slice(self.predicate.as_ref());
+        ospg[3 * TERM_ENCODING_SIZE..4 * TERM_ENCODING_SIZE]
+            .copy_from_slice(self.graph_name.as_ref());
+        ospg
+    }
+}
+
+pub struct Encoder<S: BytesStore> {
+    string_store: S,
+}
+
+impl<S: BytesStore> Encoder<S> {
+    pub fn new(string_store: S) -> Self {
+        Self { string_store }
+    }
+
+    pub fn encode_named_node(&self, named_node: &NamedNode) -> Result<EncodedTerm> {
+        let mut bytes = [0 as u8; TERM_ENCODING_SIZE];
+        bytes[0] = TYPE_NAMED_NODE_ID;
+        self.encode_str_value_to_lower_bytes(named_node.as_str(), &mut bytes)?;
+        Ok(EncodedTerm(bytes))
+    }
+
+    pub fn encode_blank_node(&self, blank_node: &BlankNode) -> Result<EncodedTerm> {
+        let mut bytes = [0 as u8; TERM_ENCODING_SIZE];
+        bytes[0] = TYPE_BLANK_NODE_ID;
+        bytes[TYPE_KEY_SIZE..TERM_ENCODING_SIZE].copy_from_slice(blank_node.as_bytes());
+        Ok(EncodedTerm(bytes))
+    }
+
+    pub fn encode_literal(&self, literal: &Literal) -> Result<EncodedTerm> {
+        let mut bytes = [0 as u8; TERM_ENCODING_SIZE];
+        if let Some(language) = literal.language() {
+            bytes[0] = TYPE_LANG_STRING_LITERAL_ID;
+            self.encode_str_value_to_upper_bytes(language, &mut bytes)?;
+        } else {
+            bytes[0] = TYPE_TYPED_LITERAL_ID;
+            self.encode_str_value_to_upper_bytes(literal.datatype().as_str(), &mut bytes)?;
+        }
+        self.encode_str_value_to_lower_bytes(literal.value().as_str(), &mut bytes)?;
+        Ok(EncodedTerm(bytes))
+    }
+
+    pub fn encode_named_or_blank_node(&self, term: &NamedOrBlankNode) -> Result<EncodedTerm> {
+        match term {
+            NamedOrBlankNode::NamedNode(named_node) => self.encode_named_node(named_node),
+            NamedOrBlankNode::BlankNode(blank_node) => self.encode_blank_node(blank_node),
+        }
+    }
+
+    pub fn encode_optional_named_or_blank_node(
+        &self,
+        term: &Option<NamedOrBlankNode>,
+    ) -> Result<EncodedTerm> {
+        match term {
+            Some(node) => self.encode_named_or_blank_node(node),
+            None => Ok(EncodedTerm(EMPTY_TERM)),
+        }
+    }
+
+    pub fn encode_term(&self, term: &Term) -> Result<EncodedTerm> {
+        match term {
+            Term::NamedNode(named_node) => self.encode_named_node(named_node),
+            Term::BlankNode(blank_node) => self.encode_blank_node(blank_node),
+            Term::Literal(literal) => self.encode_literal(literal),
+        }
+    }
+
+    pub fn encode_quad(&self, quad: &Quad) -> Result<EncodedQuad> {
+        Ok(EncodedQuad {
+            subject: self.encode_named_or_blank_node(quad.subject())?,
+            predicate: self.encode_named_node(quad.predicate())?,
+            object: self.encode_term(quad.object())?,
+            graph_name: self.encode_optional_named_or_blank_node(quad.graph_name())?,
+        })
+    }
+
+    pub fn decode_term(&self, encoded: impl AsRef<[u8]>) -> Result<Term> {
+        let encoding = encoded.as_ref();
+        match encoding[0] {
+            TYPE_NAMED_NODE_ID => {
+                let iri = self.decode_url_value_from_lower_bytes(encoding)?;
+                Ok(NamedNode::from(iri).into())
+            }
+            TYPE_BLANK_NODE_ID => Ok(BlankNode::from(Uuid::from_bytes(&encoding[1..])?).into()),
+            TYPE_LANG_STRING_LITERAL_ID => {
+                let value = self.decode_str_value_from_lower_bytes(encoding)?;
+                let language = self.decode_str_value_from_upper_bytes(encoding)?;
+                Ok(Literal::new_language_tagged_literal(value, language).into())
+            }
+            TYPE_TYPED_LITERAL_ID => {
+                let value = self.decode_str_value_from_lower_bytes(encoding)?;
+                let datatype = NamedNode::from(self.decode_url_value_from_upper_bytes(encoding)?);
+                Ok(Literal::new_typed_literal(value, datatype).into())
+            }
+            _ => Err("invalid term type encoding".into()),
+        }
+    }
+
+    pub fn decode_named_or_blank_node(
+        &self,
+        encoded: impl AsRef<[u8]>,
+    ) -> Result<NamedOrBlankNode> {
+        let encoding = encoded.as_ref();
+        match self.decode_term(encoding)? {
+            Term::NamedNode(named_node) => Ok(named_node.into()),
+            Term::BlankNode(blank_node) => Ok(blank_node.into()),
+            Term::Literal(_) => Err("A literal has ben found instead of a named node".into()),
+        }
+    }
+
+    pub fn decode_optional_named_or_blank_node(
+        &self,
+        encoded: impl AsRef<[u8]>,
+    ) -> Result<Option<NamedOrBlankNode>> {
+        let encoding = encoded.as_ref();
+        if encoding == EMPTY_TERM {
+            Ok(None)
+        } else {
+            Ok(Some(self.decode_named_or_blank_node(encoding)?))
+        }
+    }
+
+    pub fn decode_named_node(&self, encoded: impl AsRef<[u8]>) -> Result<NamedNode> {
+        let encoding = encoded.as_ref();
+        match self.decode_term(encoding)? {
+            Term::NamedNode(named_node) => Ok(named_node),
+            Term::BlankNode(_) => Err("A blank node has been found instead of a named node".into()),
+            Term::Literal(_) => Err("A literal has ben found instead of a named node".into()),
+        }
+    }
+
+    pub fn decode_quad(&self, encoded: EncodedQuad) -> Result<Quad> {
+        Ok(Quad::new(
+            self.decode_named_or_blank_node(encoded.subject)?,
+            self.decode_named_node(encoded.predicate)?,
+            self.decode_term(encoded.object)?,
+            self.decode_optional_named_or_blank_node(encoded.graph_name)?,
+        ))
+    }
+
+    fn encode_str_value_to_upper_bytes(&self, text: &str, bytes: &mut [u8]) -> Result<()> {
+        self.string_store.put(
+            text.as_bytes(),
+            &mut bytes[TYPE_KEY_SIZE..TYPE_KEY_SIZE + STRING_KEY_SIZE],
+        )
+    }
+    fn encode_str_value_to_lower_bytes(&self, text: &str, bytes: &mut [u8]) -> Result<()> {
+        self.string_store.put(
+            text.as_bytes(),
+            &mut bytes[TYPE_KEY_SIZE + STRING_KEY_SIZE..TYPE_KEY_SIZE + 2 * STRING_KEY_SIZE],
+        )
+    }
+
+    fn decode_str_value_from_upper_bytes(&self, encoding: &[u8]) -> Result<String> {
+        let bytes = self.decode_value_from_upper_bytes(encoding)?;
+        Ok(str::from_utf8(&bytes)?.to_string())
+    }
+
+    fn decode_url_value_from_upper_bytes(&self, encoding: &[u8]) -> Result<Url> {
+        let bytes = self.decode_value_from_upper_bytes(encoding)?;
+        Ok(Url::from_str(str::from_utf8(&bytes)?)?)
+    }
+
+    fn decode_value_from_upper_bytes(&self, encoding: &[u8]) -> Result<S::BytesOutput> {
+        self.string_store
+            .get(&encoding[TYPE_KEY_SIZE..TYPE_KEY_SIZE + STRING_KEY_SIZE])?
+            .ok_or(Error::from("value not found in the dictionary"))
+    }
+
+    fn decode_str_value_from_lower_bytes(&self, encoding: &[u8]) -> Result<String> {
+        let bytes = self.decode_value_from_lower_bytes(encoding)?;
+        Ok(str::from_utf8(&bytes)?.to_string())
+    }
+
+    fn decode_url_value_from_lower_bytes(&self, encoding: &[u8]) -> Result<Url> {
+        let bytes = self.decode_value_from_lower_bytes(encoding)?;
+        Ok(Url::from_str(str::from_utf8(&bytes)?)?)
+    }
+
+    fn decode_value_from_lower_bytes(&self, encoding: &[u8]) -> Result<S::BytesOutput> {
+        self.string_store
+            .get(&encoding[TYPE_KEY_SIZE + STRING_KEY_SIZE..TYPE_KEY_SIZE + 2 * STRING_KEY_SIZE])?
+            .ok_or(Error::from("value not found in the dictionary"))
+    }
+}
+
+impl<S: BytesStore + Default> Default for Encoder<S> {
+    fn default() -> Self {
+        Self {
+            string_store: S::default(),
+        }
+    }
+}
+
+mod test {
+    use errors::*;
+    use model::*;
+    use std::cell::RefCell;
+    use std::collections::BTreeMap;
+    use std::str::FromStr;
+    use store::numeric_encoder::BytesStore;
+    use store::numeric_encoder::Encoder;
+    use store::numeric_encoder::STRING_KEY_SIZE;
+    use store::numeric_encoder::TERM_ENCODING_SIZE;
+    use utils::to_bytes;
+
+    #[derive(Default)]
+    struct MemoryBytesStore {
+        id2str: RefCell<BTreeMap<[u8; STRING_KEY_SIZE], Vec<u8>>>,
+        str2id: RefCell<BTreeMap<Vec<u8>, [u8; STRING_KEY_SIZE]>>,
+    }
+
+    impl BytesStore for MemoryBytesStore {
+        type BytesOutput = Vec<u8>;
+
+        fn put(&self, value: &[u8], id_buffer: &mut [u8]) -> Result<()> {
+            let mut str2id = self.str2id.borrow_mut();
+            let mut id2str = self.id2str.borrow_mut();
+            let id = str2id.entry(value.to_vec()).or_insert_with(|| {
+                let id = to_bytes(id2str.len());
+                id2str.insert(id, value.to_vec());
+                id
+            });
+            id_buffer.copy_from_slice(id);
+            Ok(())
+        }
+
+        fn get(&self, id: &[u8]) -> Result<Option<Vec<u8>>> {
+            Ok(self.id2str.borrow().get(id).map(|s| s.to_owned()))
+        }
+    }
+
+    #[test]
+    fn test_encoding() {
+        let encoder: Encoder<MemoryBytesStore> = Encoder::default();
+        let terms: Vec<Term> = vec![
+            NamedNode::from_str("http://foo.com").unwrap().into(),
+            NamedNode::from_str("http://bar.com").unwrap().into(),
+            NamedNode::from_str("http://foo.com").unwrap().into(),
+            BlankNode::default().into(),
+            Literal::from(true).into(),
+            Literal::from(1.2).into(),
+            Literal::from("foo").into(),
+            Literal::new_language_tagged_literal("foo", "fr").into(),
+        ];
+        for term in terms {
+            let encoded = encoder.encode_term(&term).unwrap();
+            assert_eq!(term, encoder.decode_term(encoded).unwrap())
+        }
+    }
+
+}

src/store/rocksdb.rs

@@ -0,0 +1,446 @@
+use errors::*;
+use model::*;
+use rocksdb::ColumnFamily;
+use rocksdb::DBRawIterator;
+use rocksdb::DBVector;
+use rocksdb::IteratorMode;
+use rocksdb::Options;
+use rocksdb::WriteBatch;
+use rocksdb::DB;
+use std::ops::Deref;
+use std::path::Path;
+use std::slice;
+use std::str;
+use store::numeric_encoder::BytesStore;
+use store::numeric_encoder::EncodedQuad;
+use store::numeric_encoder::EncodedTerm;
+use store::numeric_encoder::Encoder;
+use store::numeric_encoder::STRING_KEY_SIZE;
+use store::numeric_encoder::TERM_ENCODING_SIZE;
+use utils::to_bytes;
+
+pub struct RocksDbDataset {
+    store: RocksDbStore,
+}
+
+impl RocksDbDataset {
+    pub fn open(path: impl AsRef<Path>) -> Result<Self> {
+        Ok(Self {
+            store: RocksDbStore::open(path)?,
+        })
+    }
+
+    fn graph(&self, name: &NamedOrBlankNode) -> RocksDbGraph {
+        RocksDbGraph {
+            store: &self.store,
+            name: name.clone(),
+        }
+    }
+
+    fn default_graph(&self) -> RocksDbDefaultGraph {
+        RocksDbDefaultGraph { store: &self.store }
+    }
+
+    fn union_graph(&self) -> RocksDbUnionGraph {
+        RocksDbUnionGraph { store: &self.store }
+    }
+
+    fn iter(&self) -> Result<QuadsIterator<SPOGIndexIterator>> {
+        Ok(QuadsIterator {
+            iter: self.store.quads()?,
+            encoder: self.store.encoder(),
+        })
+    }
+
+    fn quads_for_subject(
+        &self,
+        subject: &NamedOrBlankNode,
+    ) -> Result<QuadsIterator<FilteringEncodedQuadsIterator<SPOGIndexIterator>>> {
+        Ok(QuadsIterator {
+            iter: self.store
+                .quads_for_subject(self.store.encoder().encode_named_or_blank_node(subject)?)?,
+            encoder: self.store.encoder(),
+        })
+    }
+
+    fn contains(&self, quad: &Quad) -> Result<bool> {
+        self.store
+            .contains(&self.store.encoder().encode_quad(quad)?)
+    }
+
+    fn insert(&self, quad: &Quad) -> Result<()> {
+        self.store.insert(&self.store.encoder().encode_quad(quad)?)
+    }
+
+    fn remove(&self, quad: &Quad) -> Result<()> {
+        self.store.remove(&self.store.encoder().encode_quad(quad)?)
+    }
+}
+
+struct RocksDbGraph<'a> {
+    store: &'a RocksDbStore,
+    name: NamedOrBlankNode, //TODO: better storage
+}
+
+struct RocksDbDefaultGraph<'a> {
+    store: &'a RocksDbStore,
+}
+
+struct RocksDbUnionGraph<'a> {
+    store: &'a RocksDbStore,
+}
+
+const ID2STR_CF: &'static str = "id2str";
+const STR2ID_CF: &'static str = "id2str";
+const SPOG_CF: &'static str = "spog";
+const POSG_CF: &'static str = "posg";
+const OSPG_CF: &'static str = "ospg";
+
+const EMPTY_BUF: [u8; 0] = [0 as u8; 0];
+
+//TODO: indexes for the default graph and indexes for the named graphs (no more Optional and space saving)
+
+const COLUMN_FAMILIES: [&'static str; 5] = [ID2STR_CF, STR2ID_CF, SPOG_CF, POSG_CF, OSPG_CF];
+
+struct RocksDbStore {
+    db: DB,
+    id2str_cf: ColumnFamily,
+    str2id_cf: ColumnFamily,
+    spog_cf: ColumnFamily,
+    posg_cf: ColumnFamily,
+    ospg_cf: ColumnFamily,
+}
+
+impl RocksDbStore {
+    fn open(path: impl AsRef<Path>) -> Result<Self> {
+        let options = Options::default();
+
+        let db = DB::open_cf(&options, path, &COLUMN_FAMILIES)?;
+        let id2str_cf = get_cf(&db, STR2ID_CF)?;
+        let str2id_cf = get_cf(&db, ID2STR_CF)?;
+        let spog_cf = get_cf(&db, SPOG_CF)?;
+        let posg_cf = get_cf(&db, POSG_CF)?;
+        let ospg_cf = get_cf(&db, OSPG_CF)?;
+
+        Ok(Self {
+            db,
+            id2str_cf,
+            str2id_cf,
+            spog_cf,
+            posg_cf,
+            ospg_cf,
+        })
+    }
+
+    fn encoder(&self) -> Encoder<RocksDbBytesStore> {
+        Encoder::new(RocksDbBytesStore(&self))
+    }
+
+    fn quads(&self) -> Result<SPOGIndexIterator> {
+        let mut iter = self.db.raw_iterator_cf(self.spog_cf)?;
+        iter.seek_to_first();
+        Ok(SPOGIndexIterator { iter })
+    }
+
+    fn quads_for_subject(
+        &self,
+        subject: EncodedTerm,
+    ) -> Result<FilteringEncodedQuadsIterator<SPOGIndexIterator>> {
+        let mut iter = self.db.raw_iterator_cf(self.spog_cf)?;
+        iter.seek(subject.as_ref());
+        Ok(FilteringEncodedQuadsIterator {
+            iter: SPOGIndexIterator { iter },
+            filter: EncodedQuadPattern::new(Some(subject), None, None, None),
+        })
+    }
+
+    fn quads_for_subject_predicate(
+        &self,
+        subject: EncodedTerm,
+        predicate: EncodedTerm,
+    ) -> Result<FilteringEncodedQuadsIterator<SPOGIndexIterator>> {
+        let mut iter = self.db.raw_iterator_cf(self.spog_cf)?;
+        iter.seek(&encode_term_pair(&subject, &predicate));
+        Ok(FilteringEncodedQuadsIterator {
+            iter: SPOGIndexIterator { iter },
+            filter: EncodedQuadPattern::new(Some(subject), Some(predicate), None, None),
+        })
+    }
+
+    fn quads_for_subject_predicate_object(
+        &self,
+        subject: EncodedTerm,
+        predicate: EncodedTerm,
+        object: EncodedTerm,
+    ) -> Result<FilteringEncodedQuadsIterator<SPOGIndexIterator>> {
+        let mut iter = self.db.raw_iterator_cf(self.spog_cf)?;
+        iter.seek(&encode_term_triple(&subject, &predicate, &object));
+        Ok(FilteringEncodedQuadsIterator {
+            iter: SPOGIndexIterator { iter },
+            filter: EncodedQuadPattern::new(Some(subject), Some(predicate), Some(object), None),
+        })
+    }
+
+    fn quads_for_predicate(
+        &self,
+        predicate: EncodedTerm,
+    ) -> Result<FilteringEncodedQuadsIterator<POSGIndexIterator>> {
+        let mut iter = self.db.raw_iterator_cf(self.posg_cf)?;
+        iter.seek(predicate.as_ref());
+        Ok(FilteringEncodedQuadsIterator {
+            iter: POSGIndexIterator { iter },
+            filter: EncodedQuadPattern::new(None, Some(predicate), None, None),
+        })
+    }
+
+    fn quads_for_predicate_object(
+        &self,
+        predicate: EncodedTerm,
+        object: EncodedTerm,
+    ) -> Result<FilteringEncodedQuadsIterator<POSGIndexIterator>> {
+        let mut iter = self.db.raw_iterator_cf(self.spog_cf)?;
+        iter.seek(&encode_term_pair(&predicate, &object));
+        Ok(FilteringEncodedQuadsIterator {
+            iter: POSGIndexIterator { iter },
+            filter: EncodedQuadPattern::new(None, Some(predicate), Some(object), None),
+        })
+    }
+
+    fn quads_for_object(
+        &self,
+        object: EncodedTerm,
+    ) -> Result<FilteringEncodedQuadsIterator<OSPGIndexIterator>> {
+        let mut iter = self.db.raw_iterator_cf(self.ospg_cf)?;
+        iter.seek(object.as_ref());
+        Ok(FilteringEncodedQuadsIterator {
+            iter: OSPGIndexIterator { iter },
+            filter: EncodedQuadPattern::new(None, None, Some(object), None),
+        })
+    }
+
+    fn contains(&self, quad: &EncodedQuad) -> Result<bool> {
+        Ok(self.db.get_cf(self.spog_cf, &quad.spog())?.is_some())
+    }
+
+    fn insert(&self, quad: &EncodedQuad) -> Result<()> {
+        let mut batch = WriteBatch::default();
+        batch.put_cf(self.spog_cf, &quad.spog(), &EMPTY_BUF)?;
+        batch.put_cf(self.posg_cf, &quad.posg(), &EMPTY_BUF)?;
+        batch.put_cf(self.ospg_cf, &quad.ospg(), &EMPTY_BUF)?;
+        Ok(self.db.write(batch)?) //TODO: check what's going on if the key already exists
+    }
+
+    fn remove(&self, quad: &EncodedQuad) -> Result<()> {
+        let mut batch = WriteBatch::default();
+        batch.delete_cf(self.spog_cf, &quad.spog())?;
+        batch.delete_cf(self.posg_cf, &quad.posg())?;
+        batch.delete_cf(self.ospg_cf, &quad.ospg())?;
+        Ok(self.db.write(batch)?)
+    }
+}
+
+fn get_cf(db: &DB, name: &str) -> Result<ColumnFamily> {
+    db.cf_handle(name)
+        .ok_or_else(|| Error::from("column family not found"))
+}
+
+struct RocksDbBytesStore<'a>(&'a RocksDbStore);
+
+impl<'a> BytesStore for RocksDbBytesStore<'a> {
+    type BytesOutput = DBVector;
+
+    fn put(&self, value: &[u8], id_buffer: &mut [u8]) -> Result<()> {
+        match self.0.db.get_cf(self.0.str2id_cf, value)? {
+            Some(id) => id_buffer.copy_from_slice(&id),
+            None => {
+                let mut batch = WriteBatch::default();
+                // TODO: id allocation
+                let id = [0 as u8; STRING_KEY_SIZE];
+                batch.put_cf(self.0.id2str_cf, &id, value)?;
+                batch.put_cf(self.0.str2id_cf, value, &id)?;
+                self.0.db.write(batch)?;
+                id_buffer.copy_from_slice(&id)
+            }
+        }
+        Ok(())
+    }
+
+    fn get(&self, id: &[u8]) -> Result<Option<DBVector>> {
+        Ok(self.0.db.get_cf(self.0.id2str_cf, id)?)
+    }
+}
+
+struct EncodedQuadPattern {
+    subject: Option<EncodedTerm>,
+    predicate: Option<EncodedTerm>,
+    object: Option<EncodedTerm>,
+    graph_name: Option<EncodedTerm>,
+}
+
+impl EncodedQuadPattern {
+    fn new(
+        subject: Option<EncodedTerm>,
+        predicate: Option<EncodedTerm>,
+        object: Option<EncodedTerm>,
+        graph_name: Option<EncodedTerm>,
+    ) -> Self {
+        Self {
+            subject,
+            predicate,
+            object,
+            graph_name,
+        }
+    }
+
+    fn filter(&self, quad: &EncodedQuad) -> bool {
+        if let Some(ref subject) = self.subject {
+            if &quad.subject != subject {
+                return false;
+            }
+        }
+        if let Some(ref predicate) = self.predicate {
+            if &quad.predicate != predicate {
+                return false;
+            }
+        }
+        if let Some(ref object) = self.object {
+            if &quad.object != object {
+                return false;
+            }
+        }
+        if let Some(ref graph_name) = self.graph_name {
+            if &quad.graph_name != graph_name {
+                return false;
+            }
+        }
+        true
+    }
+}
+
+fn encode_term_pair(t1: &EncodedTerm, t2: &EncodedTerm) -> [u8; 2 * TERM_ENCODING_SIZE] {
+    let mut bytes = [0 as u8; 2 * TERM_ENCODING_SIZE];
+    bytes[0..TERM_ENCODING_SIZE].copy_from_slice(t1.as_ref());
+    bytes[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE].copy_from_slice(t2.as_ref());
+    bytes
+}
+
+fn encode_term_triple(
+    t1: &EncodedTerm,
+    t2: &EncodedTerm,
+    t3: &EncodedTerm,
+) -> [u8; 3 * TERM_ENCODING_SIZE] {
+    let mut bytes = [0 as u8; 3 * TERM_ENCODING_SIZE];
+    bytes[0..TERM_ENCODING_SIZE].copy_from_slice(t1.as_ref());
+    bytes[TERM_ENCODING_SIZE..2 * TERM_ENCODING_SIZE].copy_from_slice(t2.as_ref());
+    bytes[2 * TERM_ENCODING_SIZE..3 * TERM_ENCODING_SIZE].copy_from_slice(t2.as_ref());
+    bytes
+}
+
+struct SPOGIndexIterator {
+    iter: DBRawIterator,
+}
+
+impl Iterator for SPOGIndexIterator {
+    type Item = Result<EncodedQuad>;
+
+    fn next(&mut self) -> Option<Result<EncodedQuad>> {
+        self.iter.next();
+        self.iter
+            .key()
+            .map(|buffer| EncodedQuad::new_from_spog_buffer(&buffer))
+    }
+}
+
+struct POSGIndexIterator {
+    iter: DBRawIterator,
+}
+
+impl Iterator for POSGIndexIterator {
+    type Item = Result<EncodedQuad>;
+
+    fn next(&mut self) -> Option<Result<EncodedQuad>> {
+        self.iter.next();
+        self.iter
+            .key()
+            .map(|buffer| EncodedQuad::new_from_posg_buffer(&buffer))
+    }
+}
+
+struct OSPGIndexIterator {
+    iter: DBRawIterator,
+}
+
+impl Iterator for OSPGIndexIterator {
+    type Item = Result<EncodedQuad>;
+
+    fn next(&mut self) -> Option<Result<EncodedQuad>> {
+        self.iter.next();
+        self.iter
+            .key()
+            .map(|buffer| EncodedQuad::new_from_ospg_buffer(&buffer))
+    }
+}
+
+struct FilteringEncodedQuadsIterator<I: Iterator<Item = Result<EncodedQuad>>> {
+    iter: I,
+    filter: EncodedQuadPattern,
+}
+
+impl<I: Iterator<Item = Result<EncodedQuad>>> Iterator for FilteringEncodedQuadsIterator<I> {
+    type Item = Result<EncodedQuad>;
+
+    fn next(&mut self) -> Option<Result<EncodedQuad>> {
+        self.iter.next().filter(|quad| match quad {
+            Ok(quad) => self.filter.filter(quad),
+            Err(e) => true,
+        })
+    }
+}
+
+struct QuadsIterator<'a, I: Iterator<Item = Result<EncodedQuad>>> {
+    iter: I,
+    encoder: Encoder<RocksDbBytesStore<'a>>,
+}
+
+impl<'a, I: Iterator<Item = Result<EncodedQuad>>> Iterator for QuadsIterator<'a, I> {
+    type Item = Result<Quad>;
+
+    fn next(&mut self) -> Option<Result<Quad>> {
+        self.iter
+            .next()
+            .map(|k| k.and_then(|quad| self.encoder.decode_quad(quad)))
+    }
+}
+
+/*fn encode_sp(
+    encoder: &Encoder<RocksDbBytesStore>,
+    subject: &NamedOrBlankNode,
+    predicate: &NamedNode,
+) -> Result<[u8; 2 * TERM_ENCODING_SIZE]> {
+    let mut sp = [0 as u8; 2 * TERM_ENCODING_SIZE];
+    encoder.encode_named_or_blank_node(subject, &mut sp)?;
+    encoder.encode_named_node(predicate, &mut sp)?;
+    Ok(sp)
+}
+
+fn encode_po(
+    encoder: &Encoder<RocksDbBytesStore>,
+    predicate: &NamedNode,
+    object: &Term,
+) -> Result<[u8; 2 * TERM_ENCODING_SIZE]> {
+    let mut po = [0 as u8; 2 * TERM_ENCODING_SIZE];
+    encoder.encode_named_node(predicate, &mut po)?;
+    encoder.encode_term(object, &mut po)?;
+    Ok(po)
+}
+
+fn encode_os(
+    encoder: &Encoder<RocksDbBytesStore>,
+    object: &Term,
+    subject: &NamedOrBlankNode,
+) -> Result<[u8; 2 * TERM_ENCODING_SIZE]> {
+    let mut po = [0 as u8; 2 * TERM_ENCODING_SIZE];
+    encoder.encode_term(object, &mut po)?;
+    encoder.encode_named_or_blank_node(subject, &mut po)?;
+    Ok(po)
+}*/

src/utils.rs

@@ -1,3 +1,6 @@
+use std::mem::size_of;
+use std::mem::transmute;
+
 pub trait Escaper {
     fn escape(&self) -> String;
 }
@@ -77,3 +80,8 @@ impl ExactSizeIterator for EscapeRDF {
         }
     }
 }
+
+pub fn to_bytes(int: usize) -> [u8; size_of::<usize>()] {
+    //TODO: remove when next rust version stabilize this method
+    unsafe { transmute(int) }
+}