fix term aggregation u32::MAX overflow issue

(cherry picked from commit 1e859fd78d)

src/aggregation/bucket/composite/collector.rs

@@ -264,7 +264,7 @@ impl SegmentCompositeCollector {
             dict.insert(
                 key,
                 IntermediateCompositeBucketEntry {
-                    doc_count: agg.count,
+                    doc_count: agg.count as u64,
                     sub_aggregation: sub_aggregation_res,
                 },
             );

src/aggregation/bucket/term_agg.rs

@@ -977,12 +977,12 @@ where
                             bucket.bucket_id,
                         )?;
                     Ok(IntermediateTermBucketEntry {
-                        doc_count: bucket.count,
+                        doc_count: bucket.count as u64,
                         sub_aggregation: sub_aggregation_res,
                     })
                 } else {
                     Ok(IntermediateTermBucketEntry {
-                        doc_count: bucket.count,
+                        doc_count: bucket.count as u64,
                         sub_aggregation: Default::default(),
                     })
                 }

src/aggregation/bucket/term_missing_agg.rs

@@ -98,7 +98,7 @@ impl SegmentAggregationCollector for TermMissingAgg {
 
         let missing_count = &self.missing_count_per_bucket[parent_bucket_id as usize];
         let mut missing_entry = IntermediateTermBucketEntry {
-            doc_count: missing_count.missing_count,
+            doc_count: missing_count.missing_count as u64,
             sub_aggregation: Default::default(),
         };
         if let Some(sub_agg) = &mut self.sub_agg {

src/aggregation/intermediate_agg_result.rs

@@ -915,7 +915,7 @@ impl IntermediateRangeBucketEntry {
 #[derive(Clone, Default, Debug, PartialEq, Serialize, Deserialize)]
 pub struct IntermediateTermBucketEntry {
     /// The number of documents in the bucket.
-    pub doc_count: u32,
+    pub doc_count: u64,
     /// The sub_aggregation in this bucket.
     pub sub_aggregation: IntermediateAggregationResults,
 }
@@ -1229,6 +1229,24 @@ mod tests {
         assert_eq!(tree_left, tree_expected);
     }
 
+    #[test]
+    fn test_term_bucket_doc_count_no_u32_overflow() {
+        // Two segments each contributing (u32::MAX - 100) docs to the same term. Summing them
+        // overflowed when doc_count was u32.
+        let per_segment = u32::MAX as u64 - 100;
+        let mut entry = IntermediateTermBucketEntry {
+            doc_count: per_segment,
+            sub_aggregation: Default::default(),
+        };
+        entry
+            .merge_fruits(IntermediateTermBucketEntry {
+                doc_count: per_segment,
+                sub_aggregation: Default::default(),
+            })
+            .unwrap();
+        assert_eq!(entry.doc_count, per_segment * 2);
+    }
+
     #[test]
     fn test_merge_fruits_tree_empty() {
         let mut tree_left = get_intermediate_tree_with_ranges(&[