add function 'flattenTuple'

src/Functions/flattenTuple.cpp

@@ -0,0 +1,68 @@
+#include <Functions/IFunction.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionHelpers.h>
+#include <DataTypes/DataTypeTuple.h>
+#include <DataTypes/ObjectUtils.h>
+#include <Columns/ColumnTuple.h>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_COLUMN;
+    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
+}
+
+namespace
+{
+
+class FunctionFlattenTuple : public IFunction
+{
+public:
+    static constexpr auto name = "flattenTuple";
+    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionFlattenTuple>(); }
+
+    String getName() const override { return name; }
+    size_t getNumberOfArguments() const override { return 1; }
+    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo &) const override { return true; }
+    bool useDefaultImplementationForConstants() const override { return true; }
+
+    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
+    {
+        const auto & type = arguments[0];
+        const auto * type_tuple = checkAndGetDataType<DataTypeTuple>(type.get());
+        if (!type_tuple || !type_tuple->haveExplicitNames())
+            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                "Argument for function '{}' must be Named Tuple. Got '{}'",
+                getName(), type->getName());
+
+        auto [paths, types] = flattenTuple(type);
+        Names names;
+        names.reserve(paths.size());
+        for (const auto & path : paths)
+            names.push_back(path.getPath());
+
+        return std::make_shared<DataTypeTuple>(types, names);
+    }
+
+    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
+    {
+        auto column = arguments.at(0).column;
+        if (!checkAndGetColumn<ColumnTuple>(column.get()))
+            throw Exception(ErrorCodes::ILLEGAL_COLUMN,
+                "Illegal column {} of first argument of function {}. Expected ColumnTuple",
+                column->getName(), getName());
+
+        return flattenTuple(column);
+    }
+};
+
+}
+
+void registerFunctionFlattenTuple(FunctionFactory & factory)
+{
+    factory.registerFunction<FunctionFlattenTuple>();
+}
+
+}

src/Functions/registerFunctionsMiscellaneous.cpp

@@ -80,6 +80,7 @@ void registerFunctionInitialQueryID(FunctionFactory & factory);
 void registerFunctionServerUUID(FunctionFactory &);
 void registerFunctionZooKeeperSessionUptime(FunctionFactory &);
 void registerFunctionGetOSKernelVersion(FunctionFactory &);
+void registerFunctionFlattenTuple(FunctionFactory &);
 
 #if USE_ICU
 void registerFunctionConvertCharset(FunctionFactory &);
@@ -166,6 +167,7 @@ void registerFunctionsMiscellaneous(FunctionFactory & factory)
     registerFunctionServerUUID(factory);
     registerFunctionZooKeeperSessionUptime(factory);
     registerFunctionGetOSKernelVersion(factory);
+    registerFunctionFlattenTuple(factory);
 
 #if USE_ICU
     registerFunctionConvertCharset(factory);

tests/queries/0_stateless/02246_flatten_tuple.reference

@@ -0,0 +1,4 @@
+([1,2],['a','b'],3,'c',4)	Tuple(`t1.a` Array(UInt32), `t1.s` Array(String), b UInt32, `t2.k` String, `t2.v` UInt32)
+Tuple(id Int8, obj Tuple(k1 Int8, k2 Tuple(k3 String, k4 Nested(k5 Int8, k6 Int8)), some Int8), s String)	Tuple(id Int8, `obj.k1` Int8, `obj.k2.k3` String, `obj.k2.k4.k5` Array(Int8), `obj.k2.k4.k6` Array(Int8), `obj.some` Int8, s String)
+1	1	2	[3,4]	[0,0]	0	foo
+2	0	str	[0]	[55]	42	bar

tests/queries/0_stateless/02246_flatten_tuple.sql

@@ -0,0 +1,22 @@
+DROP TABLE IF EXISTS t_flatten_tuple;
+DROP TABLE IF EXISTS t_flatten_object;
+
+SET flatten_nested = 0;
+
+CREATE TABLE t_flatten_tuple(t Tuple(t1 Nested(a UInt32, s String), b UInt32, t2 Tuple(k String, v UInt32))) ENGINE = Memory;
+
+INSERT INTO t_flatten_tuple VALUES (([(1, 'a'), (2, 'b')], 3, ('c', 4)));
+
+SELECT flattenTuple(t) AS ft, toTypeName(ft) FROM t_flatten_tuple;
+
+SET allow_experimental_object_type = 1;
+CREATE TABLE t_flatten_object(data JSON) ENGINE = Memory;
+
+INSERT INTO t_flatten_object VALUES ('{"id": 1, "obj": {"k1": 1, "k2": {"k3": 2, "k4": [{"k5": 3}, {"k5": 4}]}}, "s": "foo"}');
+INSERT INTO t_flatten_object VALUES ('{"id": 2, "obj": {"k2": {"k3": "str", "k4": [{"k6": 55}]}, "some": 42}, "s": "bar"}');
+
+SELECT toTypeName(data), toTypeName(flattenTuple(data)) FROM t_flatten_object LIMIT 1;
+SELECT untuple(flattenTuple(data)) FROM t_flatten_object;
+
+DROP TABLE IF EXISTS t_flatten_tuple;
+DROP TABLE IF EXISTS t_flatten_object;