Attempt to add MultiCollector back

src/collector/mod.rs

@@ -13,6 +13,9 @@ use Searcher;
 mod count_collector;
 pub use self::count_collector::CountCollector;
 
+mod multi_collector;
+pub use self::multi_collector::MultiCollector;
+
 mod top_collector;
 pub use self::top_collector::TopCollector;
 

src/collector/multi_collector.rs

@@ -0,0 +1,96 @@
+use super::Collector;
+use super::SegmentCollector;
+use DocId;
+use Result;
+use Score;
+use SegmentLocalId;
+use SegmentReader;
+use std::any::Any;
+
+pub trait AnyCollector: Collector + Any where <Self as Collector>::Child : AnySegmentCollector {
+    fn merge_children_anys(&mut self, children: Vec<Box<AnySegmentCollector>>);
+}
+
+pub trait AnySegmentCollector: SegmentCollector + Any {
+}
+
+/// Multicollector makes it possible to collect on more than one collector.
+/// It should only be used for use cases where the Collector types is unknown
+/// at compile time.
+/// If the type of the collectors is known, you should prefer to use `ChainedCollector`.
+pub struct MultiCollector<'a> {
+    collectors: Vec<&'a mut AnyCollector>,
+}
+
+impl<'a> MultiCollector<'a> {
+    /// Constructor
+    pub fn from(collectors: Vec<&'a mut AnyCollector>) -> MultiCollector {
+        MultiCollector { collectors }
+    }
+}
+
+pub struct SegmentMultiCollector {
+    segment_collectors: Vec<Box<AnySegmentCollector>>,
+}
+
+impl<'a> Collector for MultiCollector<'a> {
+    type Child = SegmentMultiCollector;
+
+    fn for_segment(&mut self, segment_local_id: u32, segment: &SegmentReader) -> Result<SegmentMultiCollector> {
+        let segment_collectors = self.collectors.iter_mut()
+            .map(|x| x.for_segment(segment_local_id, segment))
+            .collect::<Result<Vec<_>>>()?;
+        Ok(SegmentMultiCollector { segment_collectors })
+    }
+
+    fn requires_scoring(&self) -> bool {
+        self.collectors
+            .iter()
+            .any(|collector| collector.requires_scoring())
+    }
+
+    fn merge_children(&mut self, children: Vec<SegmentMultiCollector>) {
+        let mut per_collector_children =
+            (0..self.collectors.len())
+                .map(|_| Vec::with_capacity(children.len()))
+                .collect::<Vec<_>>();
+        for child in children.into_iter() {
+            for (idx, segment_collector) in child.segment_collectors.into_iter().enumerate() {
+                per_collector_children[idx].push(segment_collector);
+            }
+        }
+        for (collector, children) in self.collectors.iter_mut().zip(per_collector_children) {
+            collector.merge_children_anys(children);
+        }
+    }
+}
+
+impl SegmentCollector for SegmentMultiCollector {
+    fn collect(&mut self, doc: DocId, score: Score) {
+        for collector in &mut self.segment_collectors {
+            collector.collect(doc, score);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    use collector::{Collector, CountCollector, TopCollector};
+
+    #[test]
+    fn test_multi_collector() {
+        let mut top_collector = TopCollector::with_limit(2);
+        let mut count_collector = CountCollector::default();
+        {
+            let mut collectors =
+                MultiCollector::from(vec![&mut top_collector, &mut count_collector]);
+            collectors.collect(1, 0.2);
+            collectors.collect(2, 0.1);
+            collectors.collect(3, 0.5);
+        }
+        assert_eq!(count_collector.count(), 3);
+        assert!(top_collector.at_capacity());
+    }
+}