diff --git a/src/postings/mod.rs b/src/postings/mod.rs
index a19dd048c..c6ade2a60 100644
--- a/src/postings/mod.rs
+++ b/src/postings/mod.rs
@@ -31,7 +31,7 @@ pub use self::vec_postings::VecPostings;
 
 pub use self::segment_postings::{BlockSegmentPostings, SegmentPostings};
 pub use self::intersection::IntersectionDocSet;
-pub use self::union::UnionDocSet;
+pub use self::union::{docsets_union, UnionDocSet};
 
 pub use common::HasLen;
 
diff --git a/src/postings/postings.rs b/src/postings/postings.rs
index ac5516e2e..979640230 100644
--- a/src/postings/postings.rs
+++ b/src/postings/postings.rs
@@ -30,15 +30,3 @@ impl<TPostings: Postings> Postings for Box<TPostings> {
         unboxed.positions()
     }
 }
-//
-//impl<'a, TPostings: Postings> Postings for &'a mut TPostings {
-//    fn term_freq(&self) -> u32 {
-//        let unref: &TPostings = *self;
-//        unref.term_freq()
-//    }
-//
-//    fn positions(&self) -> &[u32] {
-//        let unref: &TPostings = *self;
-//        unref.positions()
-//    }
-//}
diff --git a/src/postings/union.rs b/src/postings/union.rs
index c4797fb66..dfe34162d 100644
--- a/src/postings/union.rs
+++ b/src/postings/union.rs
@@ -186,6 +186,22 @@ impl<TDocSet: DocSet> DocSet for UnionDocSet<TDocSet> {
 }
 
 
+pub fn docsets_union(docsets: Vec<DocSet>) -> Option<Box<DocSet>> {
+    if docsets.is_empty() {
+        None
+    } else {
+        Some(if docsets.len() == 1 {
+            docsets
+                .into_iter()
+                .next()
+                .unwrap() //< we checked the size beforehands
+        } else {
+            box UnionDocSet::from(docsets)
+        })
+    }
+
+}
+
 #[cfg(test)]
 mod tests {
 
diff --git a/src/query/exclude.rs b/src/query/exclude.rs
new file mode 100644
index 000000000..af14de022
--- /dev/null
+++ b/src/query/exclude.rs
@@ -0,0 +1,118 @@
+use query::Scorer;
+use postings::SkipResult;
+use DocSet;
+use Score;
+use DocId;
+
+#[derive(Clone, Copy)]
+enum State {
+    ExcludeOne(DocId),
+    Finished
+}
+
+pub struct ExcludeScorer<TDocSet, TDocSetExclude> {
+    underlying_docset: TDocSet,
+    excluding_docset: TDocSetExclude,
+    excluding_state: State,
+}
+
+
+impl<TDocSet, TDocSetExclude> ExcludeScorer<TDocSet, TDocSetExclude>
+    where TDocSetExclude: DocSet {
+
+    pub fn new(underlying_docset: TDocSet, mut excluding_docset: TDocSetExclude) -> ExcludeScorer<TDocSet, TDocSetExclude> {
+        let state =
+            if excluding_docset.advance() {
+                State::ExcludeOne(excluding_docset.doc())
+            } else {
+                State::Finished
+            };
+        ExcludeScorer {
+            underlying_docset,
+            excluding_docset,
+            excluding_state: state,
+        }
+    }
+}
+
+impl<TDocSet, TDocSetExclude> ExcludeScorer<TDocSet, TDocSetExclude>
+    where TDocSet: DocSet, TDocSetExclude: DocSet {
+
+    /// Returns true iff the doc is not removed.
+    ///
+    /// The method has to be called with non strictly
+    /// increasing `doc`.
+    fn accept(&mut self) -> bool {
+        let doc = self.underlying_docset.doc();
+        match self.excluding_state {
+            State::ExcludeOne(excluded_doc) => {
+                if doc == excluded_doc {
+                    return false;
+                }
+                match self.excluding_docset.skip_next(doc) {
+                    SkipResult::OverStep => {
+                        self.excluding_state = State::ExcludeOne(self.excluding_docset.doc());
+                        true
+                    }
+                    SkipResult::End => {
+                        self.excluding_state = State::Finished;
+                        true
+                    }
+                    SkipResult::Reached => {
+                        false
+                    }
+                }
+            }
+            State::Finished => {
+                true
+            }
+        }
+    }
+}
+
+impl<TDocSet, TDocSetExclude> DocSet for ExcludeScorer<TDocSet, TDocSetExclude>
+    where TDocSet: DocSet, TDocSetExclude: DocSet {
+
+    fn advance(&mut self) -> bool {
+        while self.underlying_docset.advance() {
+            if self.accept() {
+                return true;
+            }
+        }
+        false
+    }
+
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
+        let underlying_skip_result = self.underlying_docset.skip_next(target);
+        if underlying_skip_result == SkipResult::End {
+            return SkipResult::End;
+        }
+        if self.accept() {
+            underlying_skip_result
+        } else if self.advance() {
+            SkipResult::OverStep
+        } else {
+            SkipResult::End
+        }
+
+    }
+
+    fn doc(&self) -> DocId {
+        self.underlying_docset.doc()
+    }
+
+    /// `.size_hint()` directly returns the size
+    /// of the underlying docset without taking in account
+    /// the fact that docs might be deleted.
+    fn size_hint(&self) -> u32 {
+        self.underlying_docset.size_hint()
+    }
+}
+
+
+impl<TDocSet, TDocSetExclude> Scorer for ExcludeScorer<TDocSet, TDocSetExclude>
+    where TDocSet: Scorer, TDocSetExclude: Scorer {
+    fn score(&self) -> Score {
+        self.underlying_docset.score()
+    }
+}
\ No newline at end of file
diff --git a/src/query/mod.rs b/src/query/mod.rs
index eaa310596..0ea4c8583 100644
--- a/src/query/mod.rs
+++ b/src/query/mod.rs
@@ -14,7 +14,9 @@ mod phrase_query;
 mod all_query;
 mod bitset;
 mod range_query;
+mod exclude;
 
+use self::exclude::ExcludeScorer;
 pub use self::bitset::BitSetDocSet;
 pub use self::boolean_query::BooleanQuery;
 pub use self::occur_filter::OccurFilter;