Remove unnecessary QuantileTDigest layer

src/AggregateFunctions/QuantileTDigest.h

@@ -37,7 +37,7 @@ namespace ErrorCodes
   * uses asin, which slows down the algorithm a bit.
   */
 template <typename T>
-class TDigest
+class QuantileTDigest
 {
     using Value = Float32;
     using Count = Float32;
@@ -95,6 +95,14 @@ class TDigest
     BetterFloat count = 0;
     size_t unmerged = 0;
 
+    /** Linear interpolation at the point x on the line (x1, y1)..(x2, y2)
+      */
+    static Value interpolate(Value x, Value x1, Value y1, Value x2, Value y2)
+    {
+        double k = (x - x1) / (x2 - x1);
+        return y1 + k * (y2 - y1);
+    }
+
     struct RadixSortTraits
     {
         using Element = Centroid;
@@ -124,7 +132,8 @@ class TDigest
         if (unmerged > params.max_unmerged)
             compress();
     }
-    void compressBrute() {
+    void compressBrute()
+    {
         if (centroids.size() <= params.max_centroids)
             return;
         const size_t batch_size = (centroids.size() + params.max_centroids - 1) / params.max_centroids; // at least 2
@@ -256,7 +265,7 @@ public:
         addCentroid(Centroid{vx, static_cast<Count>(cnt)});
     }
 
-    void merge(const TDigest & other)
+    void merge(const QuantileTDigest & other)
     {
         for (const auto & c : other.centroids)
             addCentroid(c);
@@ -293,77 +302,21 @@ public:
         compress(); // Allows reading/writing TDigests with different epsilon/max_centroids params
     }
 
-    Count getCount()
-    {
-        return count;
-    }
-
-    const Centroids & getCentroids() const
-    {
-        return centroids;
-    }
-
-    void reset()
-    {
-        centroids.resize(0);
-        count = 0;
-        unmerged = 0;
-    }
-};
-
-template <typename T>
-class QuantileTDigest
-{
-    using Value = Float32;
-    using Count = Float32;
-
-    TDigest<T> main_tdigest;
-
-    /** Linear interpolation at the point x on the line (x1, y1)..(x2, y2)
-      */
-    static Value interpolate(Value x, Value x1, Value y1, Value x2, Value y2)
-    {
-        double k = (x - x1) / (x2 - x1);
-        return y1 + k * (y2 - y1);
-    }
-
-public:
-    void add(T x, UInt64 cnt = 1)
-    {
-        main_tdigest.add(x, cnt);
-    }
-
-    void merge(const QuantileTDigest & other)
-    {
-        main_tdigest.merge(other.main_tdigest);
-    }
-
-    void serialize(WriteBuffer & buf)
-    {
-        main_tdigest.serialize(buf);
-    }
-
-    void deserialize(ReadBuffer & buf)
-    {
-        main_tdigest.deserialize(buf);
-    }
-
     /** Calculates the quantile q [0, 1] based on the digest.
       * For an empty digest returns NaN.
       */
     template <typename ResultType>
     ResultType getImpl(Float64 level)
     {
-        auto & centroids = main_tdigest.getCentroids();
         if (centroids.empty())
             return std::is_floating_point_v<ResultType> ? NAN : 0;
 
-        main_tdigest.compress();
+        compress();
 
         if (centroids.size() == 1)
             return centroids.front().mean;
 
-        Float64 x = level * main_tdigest.getCount();
+        Float64 x = level * count;
         Float64 prev_x = 0;
         Count sum = 0;
         Value prev_mean = centroids.front().mean;
@@ -391,7 +344,6 @@ public:
     template <typename ResultType>
     void getManyImpl(const Float64 * levels, const size_t * levels_permutation, size_t size, ResultType * result)
     {
-        auto & centroids = main_tdigest.getCentroids();
         if (centroids.empty())
         {
             for (size_t result_num = 0; result_num < size; ++result_num)
@@ -399,7 +351,7 @@ public:
             return;
         }
 
-        main_tdigest.compress();
+        compress();
 
         if (centroids.size() == 1)
         {
@@ -408,7 +360,7 @@ public:
             return;
         }
 
-        Float64 x = levels[levels_permutation[0]] * main_tdigest.getCount();
+        Float64 x = levels[levels_permutation[0]] * count;
         Float64 prev_x = 0;
         Count sum = 0;
         Value prev_mean = centroids.front().mean;
@@ -426,7 +378,7 @@ public:
                 if (result_num >= size)
                     return;
 
-                x = levels[levels_permutation[result_num]] * main_tdigest.getCount();
+                x = levels[levels_permutation[result_num]] * count;
             }
 
             sum += c.count;