date_trunc function to always return DateTime type

src/Functions/date_trunc.cpp

@@ -1,6 +1,6 @@
 #include <Columns/ColumnConst.h>
-#include <Columns/ColumnsNumber.h>
 #include <Columns/ColumnString.h>
+#include <Columns/ColumnsNumber.h>
 #include <DataTypes/DataTypeDate.h>
 #include <DataTypes/DataTypeDateTime.h>
 #include <DataTypes/DataTypeInterval.h>
@@ -20,12 +20,12 @@ namespace ErrorCodes
 namespace
 {
 
-class FunctionDateTrunc : public IFunction
-{
-public:
+    class FunctionDateTrunc : public IFunction
+    {
+    public:
         static constexpr auto name = "dateTrunc";
 
-    explicit FunctionDateTrunc(ContextPtr context_) : context(context_) {}
+        explicit FunctionDateTrunc(ContextPtr context_) : context(context_) { }
 
         static FunctionPtr create(ContextPtr context) { return std::make_shared<FunctionDateTrunc>(context); }
 
@@ -39,51 +39,66 @@ public:
         {
             /// The first argument is a constant string with the name of datepart.
 
-        auto result_type_is_date = false;
+            result_type_is_date = false;
             String datepart_param;
-        auto check_first_argument = [&] {
+            auto check_first_argument = [&]
+            {
                 const ColumnConst * datepart_column = checkAndGetColumnConst<ColumnString>(arguments[0].column.get());
                 if (!datepart_column)
-                throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "First argument for function {} must be constant string: "
-                    "name of datepart", getName());
+                    throw Exception(
+                        ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                        "First argument for function {} must be constant string: "
+                        "name of datepart",
+                        getName());
 
                 datepart_param = datepart_column->getValue<String>();
                 if (datepart_param.empty())
-                throw Exception(ErrorCodes::BAD_ARGUMENTS, "First argument (name of datepart) for function {} cannot be empty",
-                    getName());
+                    throw Exception(
+                        ErrorCodes::BAD_ARGUMENTS, "First argument (name of datepart) for function {} cannot be empty", getName());
 
                 if (!IntervalKind::tryParseString(datepart_param, datepart_kind))
                     throw Exception(ErrorCodes::BAD_ARGUMENTS, "{} doesn't look like datepart name in {}", datepart_param, getName());
 
-            result_type_is_date = (datepart_kind == IntervalKind::Year)
-                || (datepart_kind == IntervalKind::Quarter) || (datepart_kind == IntervalKind::Month)
-                || (datepart_kind == IntervalKind::Week);
+                result_type_is_date = (datepart_kind == IntervalKind::Year) || (datepart_kind == IntervalKind::Quarter)
+                    || (datepart_kind == IntervalKind::Month) || (datepart_kind == IntervalKind::Week);
             };
 
             bool second_argument_is_date = false;
-        auto check_second_argument = [&] {
+            auto check_second_argument = [&]
+            {
                 if (!isDate(arguments[1].type) && !isDateTime(arguments[1].type) && !isDateTime64(arguments[1].type))
-                throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of 2nd argument of function {}. "
-                    "Should be a date or a date with time", arguments[1].type->getName(), getName());
+                    throw Exception(
+                        ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                        "Illegal type {} of 2nd argument of function {}. "
+                        "Should be a date or a date with time",
+                        arguments[1].type->getName(),
+                        getName());
 
                 second_argument_is_date = isDate(arguments[1].type);
 
-            if (second_argument_is_date && ((datepart_kind == IntervalKind::Hour)
-                || (datepart_kind == IntervalKind::Minute) || (datepart_kind == IntervalKind::Second)))
+                if (second_argument_is_date
+                    && ((datepart_kind == IntervalKind::Hour) || (datepart_kind == IntervalKind::Minute)
+                        || (datepart_kind == IntervalKind::Second)))
                     throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type Date of argument for function {}", getName());
             };
 
-        auto check_timezone_argument = [&] {
+            auto check_timezone_argument = [&]
+            {
                 if (!WhichDataType(arguments[2].type).isString())
-                throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of argument of function {}. "
+                    throw Exception(
+                        ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                        "Illegal type {} of argument of function {}. "
                         "This argument is optional and must be a constant string with timezone name",
-                    arguments[2].type->getName(), getName());
+                        arguments[2].type->getName(),
+                        getName());
 
                 if (second_argument_is_date && result_type_is_date)
-                throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                    throw Exception(
+                        ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                         "The timezone argument of function {} with datepart '{}' "
                         "is allowed only when the 2nd argument has the type DateTime",
-                                getName(), datepart_param);
+                        getName(),
+                        datepart_param);
             };
 
             if (arguments.size() == 2)
@@ -99,13 +114,15 @@ public:
             }
             else
             {
-            throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
+                throw Exception(
+                    ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
                     "Number of arguments for function {} doesn't match: passed {}, should be 2 or 3",
-                getName(), arguments.size());
+                    getName(),
+                    arguments.size());
             }
 
             if (result_type_is_date)
-            return std::make_shared<DataTypeDate>();
+                return std::make_shared<DataTypeDateTime>();
             else
                 return std::make_shared<DataTypeDateTime>(extractTimeZoneNameFromFunctionArguments(arguments, 2, 1));
         }
@@ -113,7 +130,8 @@ public:
         bool useDefaultImplementationForConstants() const override { return true; }
         ColumnNumbers getArgumentsThatAreAlwaysConstant() const override { return {0, 2}; }
 
-    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override
+        ColumnPtr
+        executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override
         {
             ColumnsWithTypeAndName temp_columns(arguments.size());
             temp_columns[0] = arguments[1];
@@ -124,27 +142,41 @@ public:
 
             auto to_start_of_interval = FunctionFactory::instance().get("toStartOfInterval", context);
 
+            ColumnPtr truncated_column;
+            auto date_type = std::make_shared<DataTypeDate>();
+
             if (arguments.size() == 2)
-            return to_start_of_interval->build(temp_columns)->execute(temp_columns, result_type, input_rows_count);
-
-        temp_columns[2] = arguments[2];
-        return to_start_of_interval->build(temp_columns)->execute(temp_columns, result_type, input_rows_count);
-    }
-
-    bool hasInformationAboutMonotonicity() const override
+                truncated_column = to_start_of_interval->build(temp_columns)
+                                       ->execute(temp_columns, result_type_is_date ? date_type : result_type, input_rows_count);
+            else
             {
-        return true;
+                temp_columns[2] = arguments[2];
+                truncated_column = to_start_of_interval->build(temp_columns)
+                                       ->execute(temp_columns, result_type_is_date ? date_type : result_type, input_rows_count);
             }
 
+            if (!result_type_is_date)
+                return truncated_column;
+
+            ColumnsWithTypeAndName temp_truncated_column(1);
+            temp_truncated_column[0] = {truncated_column, date_type, ""};
+
+            auto to_date_time_or_default = FunctionFactory::instance().get("toDateTime", context);
+            return to_date_time_or_default->build(temp_truncated_column)->execute(temp_truncated_column, result_type, input_rows_count);
+        }
+
+        bool hasInformationAboutMonotonicity() const override { return true; }
+
         Monotonicity getMonotonicityForRange(const IDataType &, const Field &, const Field &) const override
         {
-        return { .is_monotonic = true, .is_always_monotonic = true };
+            return {.is_monotonic = true, .is_always_monotonic = true};
         }
 
-private:
+    private:
         ContextPtr context;
         mutable IntervalKind::Kind datepart_kind = IntervalKind::Kind::Second;
-};
+        mutable bool result_type_is_date = false;
+    };
 
 }