fixed some wrong tests, updated docs

docs/en/sql-reference/aggregate-functions/reference/avg.md

@@ -4,5 +4,59 @@ toc_priority: 5
 
 # avg {#agg_function-avg}
 
-Calculates the average. Only works for numbers (Integral, floating-point, or Decimals).
-The result is always Float64.
+Calculates the arithmetic mean.
+
+**Syntax**
+
+``` sql
+avgWeighted(x)
+```
+
+**Parameter**
+
+-   `x` — Values.
+
+`x` must be
+[Integer](../../../sql-reference/data-types/int-uint.md),
+[floating-point](../../../sql-reference/data-types/float.md), or 
+[Decimal](../../../sql-reference/data-types/decimal.md).
+
+**Returned value**
+
+- `0` if the supplied parameter is empty.
+- Mean otherwise.
+
+**Return type** is always [Float64](../../../sql-reference/data-types/float.md).
+
+**Example**
+
+Query:
+
+``` sql
+SELECT avg(x) FROM values('x Int8', 0, 1, 2, 3, 4, 5)
+```
+
+Result:
+
+``` text
+┌─avg(x)─┐
+│    2.5 │
+└────────┘
+```
+
+**Example**
+
+Query:
+
+``` sql
+CREATE table test (t UInt8) ENGINE = Memory;
+SELECT avg(t) FROM test
+```
+
+Result:
+
+``` text
+┌─avg(x)─┐
+│      0 │
+└────────┘
+```

docs/en/sql-reference/aggregate-functions/reference/avgweighted.md

@@ -25,7 +25,7 @@ but may have different types.
 
 **Returned value**
 
--   `NaN`. If all the weights are equal to 0.
+-   `NaN` if all the weights are equal to 0 or the supplied weights parameter is empty.
 -   Weighted mean otherwise.
 
 **Return type** is always [Float64](../../../sql-reference/data-types/float.md).
@@ -63,3 +63,37 @@ Result:
 │                      8 │
 └────────────────────────┘
 ```
+
+**Example**
+
+Query:
+
+``` sql
+SELECT avgWeighted(x, w)
+FROM values('x Int8, w Int8', (0, 0), (1, 0), (10, 0))
+```
+
+Result:
+
+``` text
+┌─avgWeighted(x, weight)─┐
+│                    nan │
+└────────────────────────┘
+```
+
+**Example**
+
+Query:
+
+``` sql
+CREATE table test (t UInt8) ENGINE = Memory;
+SELECT avgWeighted(t) FROM test
+```
+
+Result:
+
+``` text
+┌─avgWeighted(x, weight)─┐
+│                    nan │
+└────────────────────────┘
+```

src/AggregateFunctions/AggregateFunctionAvg.h

@@ -10,26 +10,23 @@
 
 namespace DB
 {
-/// A type-fixed fraction represented by a pair of #Numerator and #Denominator.
-template <class Numerator, class Denominator>
+
+/// @tparam BothZeroMeansNaN If false, the pair 0 / 0 = 0, nan otherwise.
+template <class Denominator, bool BothZeroMeansNaN = true>
 struct RationalFraction
 {
-   constexpr RationalFraction(): numerator(0), denominator(0) {}
+    Float64 numerator{0};
+    Denominator denominator{0};
 
-    Numerator numerator;
-    Denominator denominator;
-
-    /// Calculate the fraction as a #Result.
-    template <class Result>
-    Result NO_SANITIZE_UNDEFINED result() const
+    Float64 NO_SANITIZE_UNDEFINED result() const
     {
-        if constexpr (std::is_floating_point_v<Result> && std::numeric_limits<Result>::is_iec559)
-            return static_cast<Result>(numerator) / denominator; /// allow division by zero
+        if constexpr (BothZeroMeansNaN && std::numeric_limits<Float64>::is_iec559)
+            return static_cast<Float64>(numerator) / denominator; /// allow division by zero
 
         if (denominator == static_cast<Denominator>(0))
-            return static_cast<Result>(0);
+            return static_cast<Float64>(0);
 
-        return static_cast<Result>(numerator / denominator);
+        return static_cast<Float64>(numerator / denominator);
     }
 };
 
@@ -46,31 +43,17 @@ struct RationalFraction
  * @tparam Derived When deriving from this class, use the child class name as in CRTP, e.g.
  *         class Self : Agg<char, bool, bool, Self>.
  */
-template <class Denominator, class Derived>
+template <class Denominator, bool BothZeroMeansNaN, class Derived>
 class AggregateFunctionAvgBase : public
-        IAggregateFunctionDataHelper<RationalFraction<Float64, Denominator>, Derived>
+        IAggregateFunctionDataHelper<RationalFraction<Denominator, BothZeroMeansNaN>, Derived>
 {
 public:
-    using Numerator = Float64;
-    using Fraction = RationalFraction<Numerator, Denominator>;
-
-    using ResultType       = Float64;
-    using ResultDataType   = DataTypeNumber<Float64>;
-    using ResultVectorType = ColumnVector<Float64>;
-
+    using Fraction = RationalFraction<Denominator, BothZeroMeansNaN>;
     using Base = IAggregateFunctionDataHelper<Fraction, Derived>;
 
-    /// ctor for native types
-    explicit AggregateFunctionAvgBase(const DataTypes & argument_types_): Base(argument_types_, {}), scale(0) {}
+    explicit AggregateFunctionAvgBase(const DataTypes & argument_types_): Base(argument_types_, {}) {}
 
-    /// ctor for Decimals
-    AggregateFunctionAvgBase(const IDataType & data_type, const DataTypes & argument_types_)
-        : Base(argument_types_, {}), scale(getDecimalScale(data_type)) {}
-
-    DataTypePtr getReturnType() const override
-    {
-        return std::make_shared<ResultDataType>();
-    }
+    DataTypePtr getReturnType() const override { return std::make_shared<DataTypeNumber<Float64>>(); }
 
     void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs, Arena *) const override
     {
@@ -100,17 +83,14 @@ public:
 
     void insertResultInto(AggregateDataPtr place, IColumn & to, Arena *) const override
     {
-        static_cast<ResultVectorType &>(to).getData().push_back(this->data(place).template result<ResultType>());
+        static_cast<ColumnVector<Float64> &>(to).getData().push_back(this->data(place).result());
     }
-
-protected:
-    UInt32 scale;
 };
 
-class AggregateFunctionAvg final : public AggregateFunctionAvgBase<UInt64, AggregateFunctionAvg>
+class AggregateFunctionAvg final : public AggregateFunctionAvgBase<UInt64, false, AggregateFunctionAvg>
 {
 public:
-    using AggregateFunctionAvgBase<UInt64, AggregateFunctionAvg>::AggregateFunctionAvgBase;
+    using AggregateFunctionAvgBase<UInt64, false, AggregateFunctionAvg>::AggregateFunctionAvgBase;
 
     void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *) const final
     {

src/AggregateFunctions/AggregateFunctionAvgWeighted.h

@@ -5,10 +5,10 @@
 
 namespace DB
 {
-class AggregateFunctionAvgWeighted final : public AggregateFunctionAvgBase<Float64, AggregateFunctionAvgWeighted>
+class AggregateFunctionAvgWeighted final : public AggregateFunctionAvgBase<Float64, true, AggregateFunctionAvgWeighted>
 {
 public:
-    using AggregateFunctionAvgBase<Float64, AggregateFunctionAvgWeighted>::AggregateFunctionAvgBase;
+    using AggregateFunctionAvgBase<Float64, true, AggregateFunctionAvgWeighted>::AggregateFunctionAvgBase;
 
     void add(AggregateDataPtr place, const IColumn ** columns, size_t row_num, Arena *) const override
     {

tests/queries/0_stateless/00700_decimal_empty_aggregates.reference

@@ -5,9 +5,6 @@
 0.0000	0.0000000	0.00000000	0.0000	0.0000000	0.00000000
 0.0000	0.0000000	0.00000000	0.0000	0.0000000	0.00000000
 0.0000	0.0000000	0.00000000	0.0000	0.0000000	0.00000000
-0.0000	0.0000000	0.00000000	Decimal(9, 4)	Decimal(18, 7)	Decimal(38, 8)
-0.0000	0.0000000	0.00000000	Decimal(9, 4)	Decimal(18, 7)	Decimal(38, 8)
-0.0000	0.0000000	0.00000000	Decimal(9, 4)	Decimal(18, 7)	Decimal(38, 8)
 (0,0,0)	(0,0,0)	(0,0,0)	(0,0,0)	(0,0,0)
 0	0	0
 0	0	0

tests/queries/0_stateless/00700_decimal_empty_aggregates.sql

@@ -16,10 +16,6 @@ SELECT sum(a), sum(b), sum(c), sumWithOverflow(a), sumWithOverflow(b), sumWithOv
 SELECT sum(a+1), sum(b+1), sum(c+1), sumWithOverflow(a+1), sumWithOverflow(b+1), sumWithOverflow(c+1) FROM decimal;
 SELECT sum(a-1), sum(b-1), sum(c-1), sumWithOverflow(a-1), sumWithOverflow(b-1), sumWithOverflow(c-1) FROM decimal;
 
-SELECT avg(a) as aa, avg(b) as ab, avg(c) as ac, toTypeName(aa), toTypeName(ab),toTypeName(ac) FROM decimal;
-SELECT avg(a) as aa, avg(b) as ab, avg(c) as ac, toTypeName(aa), toTypeName(ab),toTypeName(ac) FROM decimal WHERE a > 0;
-SELECT avg(a) as aa, avg(b) as ab, avg(c) as ac, toTypeName(aa), toTypeName(ab),toTypeName(ac) FROM decimal WHERE a < 0;
-
 SELECT (uniq(a), uniq(b), uniq(c)),
     (uniqCombined(a), uniqCombined(b), uniqCombined(c)),
     (uniqCombined(17)(a), uniqCombined(17)(b), uniqCombined(17)(c)),

tests/queries/0_stateless/01035_avg.reference

@@ -0,0 +1,2 @@
+0
+499.5

tests/queries/0_stateless/01035_avg.sql

@@ -0,0 +1,9 @@
+CREATE TABLE IF NOT EXISTS test_01035 (
+    t UInt16
+) ENGINE = Memory;
+
+SELECT avg(t) FROM test_01035;
+INSERT INTO test_01035 SELECT * FROM system.numbers LIMIT 1000;
+SELECT avg(t) FROM test_01035;
+
+DROP TABLE IF EXISTS test_01035