From ee229a00125c9a4c2edff32c73ca8d952c75b1e7 Mon Sep 17 00:00:00 2001
From: Nghia Truong <nghiat@nvidia.com>
Date: Wed, 13 Sep 2023 15:24:05 -0700
Subject: [PATCH] Add binding for `HISTOGRAM` and `MERGE_HISTOGRAM`
 aggregations

---
 .../main/java/ai/rapids/cudf/Aggregation.java | 24 ++++++++++++++++++-
 .../ai/rapids/cudf/GroupByAggregation.java    |  8 +++++++
 java/src/main/native/src/AggregationJni.cpp   |  5 ++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/java/src/main/java/ai/rapids/cudf/Aggregation.java b/java/src/main/java/ai/rapids/cudf/Aggregation.java
index d10329ca0f2..029017ae113 100644
--- a/java/src/main/java/ai/rapids/cudf/Aggregation.java
+++ b/java/src/main/java/ai/rapids/cudf/Aggregation.java
@@ -68,7 +68,9 @@ enum Kind {
         DENSE_RANK(29),
         PERCENT_RANK(30),
         TDIGEST(31), // This can take a delta argument for accuracy level
-        MERGE_TDIGEST(32); // This can take a delta argument for accuracy level
+        MERGE_TDIGEST(32), // This can take a delta argument for accuracy level
+        HISTOGRAM(33),
+        MERGE_HISTOGRAM(34);
 
         final int nativeId;
 
@@ -918,6 +920,26 @@ static TDigestAggregation mergeTDigest(int delta) {
         return new TDigestAggregation(Kind.MERGE_TDIGEST, delta);
     }
 
+    static final class HistogramAggregation extends NoParamAggregation {
+        private HistogramAggregation() {
+            super(Kind.HISTOGRAM);
+        }
+    }
+
+    static final class MergeHistogramAggregation extends NoParamAggregation {
+        private MergeHistogramAggregation() {
+            super(Kind.MERGE_HISTOGRAM);
+        }
+    }
+
+    static HistogramAggregation histogram() {
+        return new HistogramAggregation();
+    }
+
+    static MergeHistogramAggregation mergeHistogram() {
+        return new MergeHistogramAggregation();
+    }
+
     /**
      * Create one of the aggregations that only needs a kind, no other parameters. This does not
      * work for all types and for code safety reasons each kind is added separately.
diff --git a/java/src/main/java/ai/rapids/cudf/GroupByAggregation.java b/java/src/main/java/ai/rapids/cudf/GroupByAggregation.java
index 500d18f7eae..25bb716bd5a 100644
--- a/java/src/main/java/ai/rapids/cudf/GroupByAggregation.java
+++ b/java/src/main/java/ai/rapids/cudf/GroupByAggregation.java
@@ -315,4 +315,12 @@ public static GroupByAggregation createTDigest(int delta) {
   public static GroupByAggregation mergeTDigest(int delta) {
     return new GroupByAggregation(Aggregation.mergeTDigest(delta));
   }
+
+  public static GroupByAggregation histogram() {
+    return new GroupByAggregation(Aggregation.histogram());
+  }
+
+  public static GroupByAggregation mergeHistogram() {
+    return new GroupByAggregation(Aggregation.mergeHistogram());
+  }
 }
diff --git a/java/src/main/native/src/AggregationJni.cpp b/java/src/main/native/src/AggregationJni.cpp
index 6ac73282615..8984c27530d 100644
--- a/java/src/main/native/src/AggregationJni.cpp
+++ b/java/src/main/native/src/AggregationJni.cpp
@@ -90,6 +90,11 @@ JNIEXPORT jlong JNICALL Java_ai_rapids_cudf_Aggregation_createNoParamAgg(JNIEnv
         case 30: // ANSI SQL PERCENT_RANK
           return cudf::make_rank_aggregation(cudf::rank_method::MIN, {}, cudf::null_policy::INCLUDE,
                                              {}, cudf::rank_percentage::ONE_NORMALIZED);
+        case 33: // HISTOGRAM
+          return cudf::make_histogram_aggregation();
+        case 34: // MERGE_HISTOGRAM
+          return cudf::make_merge_histogram_aggregation();
+
         default: throw std::logic_error("Unsupported No Parameter Aggregation Operation");
       }
     }();