Use FnvHashMap for keyed bucket entries

Author: k-yomo

src/aggregation/agg_result.rs

@@ -6,6 +6,7 @@
 
 use std::collections::HashMap;
 
+use fnv::FnvHashMap;
 use serde::{Deserialize, Serialize};
 
 use super::agg_req::BucketAggregationInternal;
@@ -145,7 +146,7 @@ pub enum BucketEntries<T> {
     /// Vector format bucket entries
     Vec(Vec<T>),
     /// HashMap format bucket entries
-    HashMap(HashMap<String, T>),
+    HashMap(FnvHashMap<String, T>),
 }
 
 /// This is the default entry for a bucket, which contains a key, count, and optionally

src/aggregation/intermediate_agg_result.rs

@@ -287,7 +287,8 @@ impl IntermediateBucketResult {
                     .expect("unexpected aggregation, expected range aggregation")
                     .keyed;
                 let buckets = if is_keyed {
-                    let mut bucket_map = HashMap::new();
+                    let mut bucket_map =
+                        FnvHashMap::with_capacity_and_hasher(buckets.len(), Default::default());
                     for bucket in buckets {
                         bucket_map.insert(bucket.key.to_string(), bucket);
                     }
@@ -306,7 +307,8 @@ impl IntermediateBucketResult {
                 )?;
 
                 let buckets = if req.as_histogram().unwrap().keyed {
-                    let mut bucket_map = HashMap::new();
+                    let mut bucket_map =
+                        FnvHashMap::with_capacity_and_hasher(buckets.len(), Default::default());
                     for bucket in buckets {
                         bucket_map.insert(bucket.key.to_string(), bucket);
                     }