Fixed "arrayWithConstant" function

dbms/src/Functions/arrayWithConstant.cpp

@@ -0,0 +1,70 @@
+#include <Functions/IFunction.h>
+#include <Functions/FunctionHelpers.h>
+#include <Functions/FunctionFactory.h>
+#include <DataTypes/DataTypeArray.h>
+#include <DataTypes/DataTypesNumber.h>
+#include <Columns/ColumnArray.h>
+
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
+}
+
+/* arrayWithConstant(num, const) - make array of constants with length num.
+ * arrayWithConstant(3, 'hello') = ['hello', 'hello', 'hello']
+ * arrayWithConstant(1, 'hello') = ['hello']
+ * arrayWithConstant(0, 'hello') = []
+ */
+
+class FunctionArrayWithConstant : public IFunction
+{
+public:
+    static constexpr auto name = "arrayWithConstant";
+
+    static FunctionPtr create(const Context &) { return std::make_shared<FunctionArrayWithConstant>(); }
+
+    String getName() const override { return name; }
+    size_t getNumberOfArguments() const override { return 2; }
+
+    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
+    {
+        if (!isNumber(arguments[0]))
+            throw Exception("Illegal type " + arguments[0]->getName() +
+                " of argument of function " + getName() +
+                ", expected Integer", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
+        return std::make_shared<DataTypeArray>(arguments[1]);
+    }
+
+    bool useDefaultImplementationForConstants() const override { return true; }
+    bool useDefaultImplementationForNulls() const override { return false; }
+
+    void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t num_rows) override
+    {
+        const auto * col_num = block.getByPosition(arguments[0]).column.get();
+        const auto * col_value = block.getByPosition(arguments[1]).column.get();
+
+        auto offsets_col = ColumnArray::ColumnOffsets::create();
+        ColumnArray::Offsets & offsets = offsets_col->getData();
+        offsets.reserve(num_rows);
+
+        ColumnArray::Offset offset = 0;
+        for (size_t i = 0; i < num_rows; ++i)
+        {
+            offset += col_num->getUInt(i);
+            offsets.push_back(offset);
+        }
+
+        block.getByPosition(result).column = ColumnArray::create(col_value->replicate(offsets), std::move(offsets_col));
+    }
+};
+
+void registerFunctionArrayWithConstant(FunctionFactory & factory)
+{
+    factory.registerFunction<FunctionArrayWithConstant>();
+}
+
+}

dbms/src/Functions/registerFunctionsArray.cpp

@@ -28,6 +28,7 @@ void registerFunctionArrayEnumerateUniq(FunctionFactory &);
 void registerFunctionArrayEnumerateDense(FunctionFactory &);
 void registerFunctionArrayUniq(FunctionFactory &);
 void registerFunctionArrayDistinct(FunctionFactory &);
+void registerFunctionArrayWithConstant(FunctionFactory &);
 
 void registerFunctionsArray(FunctionFactory & factory)
 {
@@ -56,6 +57,7 @@ void registerFunctionsArray(FunctionFactory & factory)
     registerFunctionArrayEnumerateDense(factory);
     registerFunctionArrayUniq(factory);
     registerFunctionArrayDistinct(factory);
+    registerFunctionArrayWithConstant(factory);
 }
 
 }

dbms/tests/queries/0_stateless/00903_array_with_constant_function.reference

@@ -0,0 +1 @@
+['qwerty','qwerty']	[]	[1]

dbms/tests/queries/0_stateless/00903_array_with_constant_function.sql

@@ -0,0 +1 @@
+select arrayWithConstant(2, 'qwerty'), arrayWithConstant(0, -1), arrayWithConstant(1, 1)

dbms/tests/queries/0_stateless/00904_array_with_constant_2.reference

@@ -0,0 +1,40 @@
+[0,0,0]
+[1,1,1]
+[2,2,2]
+[3,3,3]
+[4,4,4]
+[5,5,5]
+[6,6,6]
+[7,7,7]
+[8,8,8]
+[9,9,9]
+[]
+['Hello']
+['Hello','Hello']
+['Hello','Hello','Hello']
+['Hello','Hello','Hello','Hello']
+['Hello','Hello','Hello','Hello','Hello']
+['Hello','Hello','Hello','Hello','Hello','Hello']
+['Hello','Hello','Hello','Hello','Hello','Hello','Hello']
+['Hello','Hello','Hello','Hello','Hello','Hello','Hello','Hello']
+['Hello','Hello','Hello','Hello','Hello','Hello','Hello','Hello','Hello']
+[]
+['Hello']
+[NULL,NULL]
+[]
+[NULL]
+['Hello','Hello']
+[]
+['Hello']
+[NULL,NULL]
+[]
+[]
+[[]]
+[[],[]]
+[[],[],[]]
+[[],[],[],[]]
+[[],[],[],[],[]]
+[[],[],[],[],[],[]]
+[[],[],[],[],[],[],[]]
+[[],[],[],[],[],[],[],[]]
+[[],[],[],[],[],[],[],[],[]]

dbms/tests/queries/0_stateless/00904_array_with_constant_2.sql

@@ -0,0 +1,4 @@
+SELECT arrayWithConstant(3, number) FROM numbers(10);
+SELECT arrayWithConstant(number, 'Hello') FROM numbers(10);
+SELECT arrayWithConstant(number % 3, number % 2 ? 'Hello' : NULL) FROM numbers(10);
+SELECT arrayWithConstant(number, []) FROM numbers(10);