move partitions to heap

src/aggregation/cached_sub_aggs.rs

@@ -34,7 +34,6 @@ pub type LowCardCachedSubAggs = CachedSubAggs<LowCardSubAggCache>;
 pub type HighCardCachedSubAggs = CachedSubAggs<HighCardSubAggCache>;
 
 const FLUSH_THRESHOLD: usize = 2048;
-const NUM_PARTITIONS: usize = 16;
 
 /// A trait for caching sub-aggregation doc ids per bucket id.
 /// Different implementations can be used depending on the cardinality
@@ -95,6 +94,9 @@ impl<Backend: SubAggCache + Debug> CachedSubAggs<Backend> {
     }
 }
 
+/// Number of partitions for high cardinality sub-aggregation cache.
+const NUM_PARTITIONS: usize = 16;
+
 #[derive(Debug)]
 pub(crate) struct HighCardSubAggCache {
     /// This weird partitioning is used to do some cheap grouping on the bucket ids.
@@ -103,13 +105,13 @@ pub(crate) struct HighCardSubAggCache {
     ///
     /// We want to keep this cheap, because high cardinality aggregations can have a lot of
     /// buckets, and there may be nothing to group.
-    partitions: [PartitionEntry; NUM_PARTITIONS],
+    partitions: Box<[PartitionEntry; NUM_PARTITIONS]>,
 }
 
 impl HighCardSubAggCache {
     #[inline]
     fn clear(&mut self) {
-        for partition in &mut self.partitions {
+        for partition in self.partitions.iter_mut() {
             partition.clear();
         }
     }
@@ -132,7 +134,7 @@ impl PartitionEntry {
 impl SubAggCache for HighCardSubAggCache {
     fn new() -> Self {
         Self {
-            partitions: core::array::from_fn(|_| PartitionEntry::default()),
+            partitions: Box::new(core::array::from_fn(|_| PartitionEntry::default())),
         }
     }
 
@@ -150,7 +152,7 @@ impl SubAggCache for HighCardSubAggCache {
         _force: bool,
     ) -> crate::Result<()> {
         let mut max_bucket = 0u32;
-        for partition in &self.partitions {
+        for partition in self.partitions.iter() {
             if let Some(&local_max) = partition.bucket_ids.iter().max() {
                 max_bucket = max_bucket.max(local_max);
             }
@@ -158,7 +160,7 @@ impl SubAggCache for HighCardSubAggCache {
 
         sub_agg.prepare_max_bucket(max_bucket, agg_data)?;
 
-        for slot in &self.partitions {
+        for slot in self.partitions.iter() {
             if !slot.bucket_ids.is_empty() {
                 // Reduce dynamic dispatch overhead by collecting a full partition in one call.
                 sub_agg.collect_multiple(&slot.bucket_ids, &slot.docs, agg_data)?;