return Option from as_ methods

src/aggregation/agg_req.rs

@@ -100,16 +100,16 @@ pub(crate) struct BucketAggregationInternal {
 }
 
 impl BucketAggregationInternal {
-    pub(crate) fn as_histogram(&self) -> &HistogramAggregation {
+    pub(crate) fn as_histogram(&self) -> Option<&HistogramAggregation> {
         match &self.bucket_agg {
-            BucketAggregationType::Histogram(histogram) => histogram,
-            _ => panic!("unexpected aggregation"),
+            BucketAggregationType::Histogram(histogram) => Some(histogram),
+            _ => None,
         }
     }
-    pub(crate) fn as_term(&self) -> &TermsAggregation {
+    pub(crate) fn as_term(&self) -> Option<&TermsAggregation> {
         match &self.bucket_agg {
-            BucketAggregationType::Terms(terms) => terms,
-            _ => panic!("unexpected aggregation"),
+            BucketAggregationType::Terms(terms) => Some(terms),
+            _ => None,
         }
     }
 }

src/aggregation/agg_result.rs

@@ -179,15 +179,16 @@ impl BucketResult {
             IntermediateBucketResult::Histogram { buckets } => {
                 let buckets = intermediate_buckets_to_final_buckets(
                     buckets,
-                    req.as_histogram(),
+                    req.as_histogram().expect("unexpected aggregation"),
                     &req.sub_aggregation,
                 );
 
                 BucketResult::Histogram { buckets }
             }
-            IntermediateBucketResult::Terms(terms) => {
-                terms.into_final_result(req.as_term(), &req.sub_aggregation)
-            }
+            IntermediateBucketResult::Terms(terms) => terms.into_final_result(
+                req.as_term().expect("unexpected aggregation"),
+                &req.sub_aggregation,
+            ),
         }
     }
 }

src/aggregation/bucket/term_agg.rs

@@ -51,6 +51,9 @@ use crate::DocId;
 ///
 /// # Limitations/Compatibility
 ///
+/// Each segment returns up to [segment_size](TermsAggregation::segment_size) results. This
+/// differences to elasticsearch behaviour.
+///
 /// # Request JSON Format
 /// ```json
 /// {
@@ -87,6 +90,8 @@ pub struct TermsAggregation {
     /// include doc_count_error_upper_bound, which is an upper bound to the error on the
     /// doc_count returned by each shard. It’s the sum of the size of the largest bucket on
     /// each segment that didn’t fit into `shard_size`.
+    ///
+    /// Defaults to true.
     #[serde(default = "default_show_term_doc_count_error")]
     pub show_term_doc_count_error: bool,