Spark sql avg agg function support decimal (facebookincubator#6020)

Revert "Fix decimal agg signature on partial companion function (oap-project#465)"

This reverts commit 336d61f.

velox/functions/lib/aggregates/AverageAggregateBase.cpp

@@ -21,14 +21,16 @@ namespace facebook::velox::functions::aggregate {
 void checkAvgIntermediateType(const TypePtr& type) {
   VELOX_USER_CHECK(
       type->isRow() || type->isVarbinary(),
-      "Input type for final average must be row type or varbinary type.");
+      "Input type for final average must be row type or varbinary type, find {}",
+      type->toString());
   if (type->kind() == TypeKind::VARBINARY) {
     return;
   }
   VELOX_USER_CHECK(
       type->childAt(0)->kind() == TypeKind::DOUBLE ||
           type->childAt(0)->isLongDecimal(),
-      "Input type for sum in final average must be double or long decimal type.")
+      "Input type for sum in final average must be double or long decimal type, find {}",
+      type->childAt(0)->toString());
   VELOX_USER_CHECK_EQ(
       type->childAt(1)->kind(),
       TypeKind::BIGINT,

velox/functions/lib/aggregates/DecimalAggregate.h

@@ -74,11 +74,11 @@ class DecimalAggregate : public exec::Aggregate {
   explicit DecimalAggregate(TypePtr resultType) : exec::Aggregate(resultType) {}
 
   int32_t accumulatorFixedWidthSize() const override {
-    return sizeof(DecimalAggregate);
+    return sizeof(LongDecimalWithOverflowState);
   }
 
   int32_t accumulatorAlignmentSize() const override {
-    return static_cast<int32_t>(sizeof(int128_t));
+    return alignof(LongDecimalWithOverflowState);
   }
 
   void initializeNewGroups(
@@ -287,7 +287,9 @@ class DecimalAggregate : public exec::Aggregate {
   }
 
   virtual TResultType computeFinalValue(
-      LongDecimalWithOverflowState* accumulator) = 0;
+      LongDecimalWithOverflowState* accumulator) {
+    return 0;
+  };
 
   void extractValues(char** groups, int32_t numGroups, VectorPtr* result)
       override {
@@ -329,11 +331,12 @@ class DecimalAggregate : public exec::Aggregate {
     accumulator->count += 1;
   }
 
- private:
+ protected:
   inline LongDecimalWithOverflowState* decimalAccumulator(char* group) {
     return exec::Aggregate::value<LongDecimalWithOverflowState>(group);
   }
 
+ private:
   DecodedVector decodedRaw_;
   DecodedVector decodedPartial_;
 };