diff --git a/src/data/doc_ids.rs b/src/data/doc_ids.rs
index 7c8613744..11bc9fe75 100644
--- a/src/data/doc_ids.rs
+++ b/src/data/doc_ids.rs
@@ -4,6 +4,7 @@ use std::path::Path;
 use std::sync::Arc;
 use std::{io, mem};
 
+use sdset::Set;
 use fst::raw::MmapReadOnly;
 use serde::ser::{Serialize, Serializer};
 
@@ -42,11 +43,12 @@ impl DocIds {
         self.doc_ids().binary_search(&doc).is_ok()
     }
 
-    pub fn doc_ids(&self) -> &[DocumentId] {
+    pub fn doc_ids(&self) -> &Set<DocumentId> {
         let slice = &self.data;
         let ptr = slice.as_ptr() as *const DocumentId;
         let len = slice.len() / mem::size_of::<DocumentId>();
-        unsafe { from_raw_parts(ptr, len) }
+        let slice = unsafe { from_raw_parts(ptr, len) };
+        Set::new_unchecked(slice)
     }
 }
 
diff --git a/src/data/doc_indexes.rs b/src/data/doc_indexes.rs
index c7a73a149..832740e4e 100644
--- a/src/data/doc_indexes.rs
+++ b/src/data/doc_indexes.rs
@@ -5,8 +5,9 @@ use std::ops::Index;
 use std::path::Path;
 use std::sync::Arc;
 
-use fst::raw::MmapReadOnly;
 use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
+use fst::raw::MmapReadOnly;
+use sdset::Set;
 
 use crate::DocIndex;
 use crate::data::Data;
@@ -64,11 +65,12 @@ impl DocIndexes {
         bytes
     }
 
-    pub fn get(&self, index: usize) -> Option<&[DocIndex]> {
+    pub fn get(&self, index: usize) -> Option<&Set<DocIndex>> {
         self.ranges().get(index as usize).map(|Range { start, end }| {
             let start = *start as usize;
             let end = *end as usize;
-            &self.indexes()[start..end]
+            let slice = &self.indexes()[start..end];
+            Set::new_unchecked(slice)
         })
     }
 
@@ -117,7 +119,7 @@ impl<W: Write> DocIndexesBuilder<W> {
         }
     }
 
-    pub fn insert(&mut self, indexes: &[DocIndex]) -> io::Result<()> {
+    pub fn insert(&mut self, indexes: &Set<DocIndex>) -> io::Result<()> {
         let len = indexes.len() as u64;
         let start = self.ranges.last().map(|r| r.end).unwrap_or(0);
         let range = Range { start, end: start + len };
@@ -164,16 +166,16 @@ mod tests {
 
         let mut builder = DocIndexesBuilder::memory();
 
-        builder.insert(&[a])?;
-        builder.insert(&[a, b, c])?;
-        builder.insert(&[a, c])?;
+        builder.insert(Set::new(&[a])?)?;
+        builder.insert(Set::new(&[a, b, c])?)?;
+        builder.insert(Set::new(&[a, c])?)?;
 
         let bytes = builder.into_inner()?;
         let docs = DocIndexes::from_bytes(bytes)?;
 
-        assert_eq!(docs.get(0), Some(&[a][..]));
-        assert_eq!(docs.get(1), Some(&[a, b, c][..]));
-        assert_eq!(docs.get(2), Some(&[a, c][..]));
+        assert_eq!(docs.get(0), Some(Set::new(&[a])?));
+        assert_eq!(docs.get(1), Some(Set::new(&[a, b, c])?));
+        assert_eq!(docs.get(2), Some(Set::new(&[a, c])?));
         assert_eq!(docs.get(3), None);
 
         Ok(())
@@ -187,9 +189,9 @@ mod tests {
 
         let mut builder = DocIndexesBuilder::memory();
 
-        builder.insert(&[a])?;
-        builder.insert(&[a, b, c])?;
-        builder.insert(&[a, c])?;
+        builder.insert(Set::new(&[a])?)?;
+        builder.insert(Set::new(&[a, b, c])?)?;
+        builder.insert(Set::new(&[a, c])?)?;
 
         let builder_bytes = builder.into_inner()?;
         let docs = DocIndexes::from_bytes(builder_bytes.clone())?;
diff --git a/src/database/blob/negative/blob.rs b/src/database/blob/negative/blob.rs
index 038c90cf2..04b655b55 100644
--- a/src/database/blob/negative/blob.rs
+++ b/src/database/blob/negative/blob.rs
@@ -2,6 +2,7 @@ use std::error::Error;
 use std::path::Path;
 use std::fmt;
 
+use sdset::Set;
 use serde::de::{self, Deserialize, Deserializer};
 use serde::ser::{Serialize, Serializer};
 use crate::data::DocIds;
@@ -38,8 +39,8 @@ impl NegativeBlob {
     }
 }
 
-impl AsRef<[DocumentId]> for NegativeBlob {
-    fn as_ref(&self) -> &[DocumentId] {
+impl AsRef<Set<DocumentId>> for NegativeBlob {
+    fn as_ref(&self) -> &Set<DocumentId> {
         self.as_ids().doc_ids()
     }
 }
@@ -47,7 +48,7 @@ impl AsRef<[DocumentId]> for NegativeBlob {
 impl fmt::Debug for NegativeBlob {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "NegativeBlob(")?;
-        f.debug_list().entries(self.as_ref()).finish()?;
+        f.debug_list().entries(self.as_ref().as_slice()).finish()?;
         write!(f, ")")
     }
 }
diff --git a/src/database/blob/ops.rs b/src/database/blob/ops.rs
index b752739f7..0aeea037d 100644
--- a/src/database/blob/ops.rs
+++ b/src/database/blob/ops.rs
@@ -1,9 +1,9 @@
 use std::error::Error;
 
 use fst::{IntoStreamer, Streamer};
-use group_by::GroupBy;
 use sdset::duo::DifferenceByKey;
 use sdset::{Set, SetOperation};
+use group_by::GroupBy;
 
 use crate::database::blob::{Blob, Sign, PositiveBlob, PositiveBlobBuilder, NegativeBlob};
 use crate::database::blob::{positive, negative};
@@ -89,18 +89,16 @@ impl OpBuilder {
             };
 
             let mut builder = PositiveBlobBuilder::memory();
-            let doc_ids = Set::new_unchecked(negative.as_ref());
 
             let op_builder = positive::OpBuilder::new().add(&base).add(&positive);
             let mut stream = op_builder.union().into_stream();
             while let Some((input, doc_indexes)) = stream.next() {
-                let doc_indexes = Set::new_unchecked(doc_indexes);
-                let op = DifferenceByKey::new(doc_indexes, doc_ids, |x| x.document_id, |x| *x);
+                let op = DifferenceByKey::new(doc_indexes, negative.as_ref(), |x| x.document_id, |x| *x);
 
                 buffer.clear();
                 op.extend_vec(&mut buffer);
                 if !buffer.is_empty() {
-                    builder.insert(input, &buffer)?;
+                    builder.insert(input, Set::new_unchecked(&buffer))?;
                 }
             }
 
diff --git a/src/database/blob/positive/blob.rs b/src/database/blob/positive/blob.rs
index b58bee7a2..fd6f2251d 100644
--- a/src/database/blob/positive/blob.rs
+++ b/src/database/blob/positive/blob.rs
@@ -4,6 +4,7 @@ use std::path::Path;
 use std::error::Error;
 
 use fst::{map, Map, Streamer, IntoStreamer};
+use sdset::Set;
 
 use crate::DocIndex;
 use crate::data::{DocIndexes, DocIndexesBuilder};
@@ -177,7 +178,7 @@ impl<W: Write, X: Write> PositiveBlobBuilder<W, X> {
     /// then an error is returned. Similarly, if there was a problem writing
     /// to the underlying writer, an error is returned.
     // FIXME what if one write doesn't work but the other do ?
-    pub fn insert<K>(&mut self, key: K, doc_indexes: &[DocIndex]) -> Result<(), Box<Error>>
+    pub fn insert<K>(&mut self, key: K, doc_indexes: &Set<DocIndex>) -> Result<(), Box<Error>>
     where K: AsRef<[u8]>,
     {
         self.map.insert(key, self.value)?;
@@ -210,9 +211,9 @@ mod tests {
 
         let mut builder = PositiveBlobBuilder::memory();
 
-        builder.insert("aaa", &[a])?;
-        builder.insert("aab", &[a, b, c])?;
-        builder.insert("aac", &[a, c])?;
+        builder.insert("aaa", Set::new(&[a])?)?;
+        builder.insert("aab", Set::new(&[a, b, c])?)?;
+        builder.insert("aac", Set::new(&[a, c])?)?;
 
         let (map_bytes, indexes_bytes) = builder.into_inner()?;
         let positive_blob = PositiveBlob::from_bytes(map_bytes, indexes_bytes)?;
@@ -233,9 +234,9 @@ mod tests {
 
         let mut builder = PositiveBlobBuilder::memory();
 
-        builder.insert("aaa", &[a])?;
-        builder.insert("aab", &[a, b, c])?;
-        builder.insert("aac", &[a, c])?;
+        builder.insert("aaa", Set::new(&[a])?)?;
+        builder.insert("aab", Set::new(&[a, b, c])?)?;
+        builder.insert("aac", Set::new(&[a, c])?)?;
 
         let (map_bytes, indexes_bytes) = builder.into_inner()?;
         let positive_blob = PositiveBlob::from_bytes(map_bytes, indexes_bytes)?;
diff --git a/src/database/blob/positive/ops.rs b/src/database/blob/positive/ops.rs
index e94ebdc0d..ffd66cead 100644
--- a/src/database/blob/positive/ops.rs
+++ b/src/database/blob/positive/ops.rs
@@ -74,7 +74,7 @@ impl<'m> $name<'m> {
 }
 
 impl<'m, 'a> fst::Streamer<'a> for $name<'m> {
-    type Item = (&'a [u8], &'a [DocIndex]);
+    type Item = (&'a [u8], &'a Set<DocIndex>);
 
     fn next(&'a mut self) -> Option<Self::Item> {
         // loop {
@@ -114,7 +114,7 @@ impl<'m, 'a> fst::Streamer<'a> for $name<'m> {
                 builder.$operation().extend_vec(&mut self.outs);
 
                 if self.outs.is_empty() { return None }
-                return Some((input, &self.outs))
+                return Some((input, Set::new_unchecked(&self.outs)))
             },
             None => None
         }
diff --git a/src/database/update/negative/update.rs b/src/database/update/negative/update.rs
index 222a29a2c..3d4c4d061 100644
--- a/src/database/update/negative/update.rs
+++ b/src/database/update/negative/update.rs
@@ -48,9 +48,9 @@ impl NegativeUpdateBuilder {
             Blob::Positive(_) => unreachable!(),
         };
 
-        for &document_id in negative_blob.as_ref() {
+        for &document_id in negative_blob.as_ref().as_slice() {
             let start = DocumentKey::new(document_id);
-            let end = DocumentKey::new(document_id + 1);
+            let end = start.with_attribute_max();
             file_writer.delete_range(start.as_ref(), end.as_ref())?;
         }
 
diff --git a/src/database/update/positive/unordered_builder.rs b/src/database/update/positive/unordered_builder.rs
index 7a2139c98..6b9dc5abe 100644
--- a/src/database/update/positive/unordered_builder.rs
+++ b/src/database/update/positive/unordered_builder.rs
@@ -4,6 +4,8 @@ use std::collections::BTreeMap;
 use std::error::Error;
 use std::io::Write;
 
+use sdset::Set;
+
 use crate::database::blob::positive::PositiveBlobBuilder;
 use crate::DocIndex;
 
@@ -40,7 +42,7 @@ impl<W: Write, X: Write> UnorderedPositiveBlobBuilder<W, X> {
     pub fn into_inner(mut self) -> Result<(W, X), Box<Error>> {
         for (key, mut doc_indexes) in self.map {
             doc_indexes.sort_unstable();
-            self.builder.insert(&key, &doc_indexes)?;
+            self.builder.insert(&key, Set::new_unchecked(&doc_indexes))?;
         }
         self.builder.into_inner()
     }