Some fixups

docs/en/operations/settings/settings.md

@@ -4386,7 +4386,7 @@ Default value: `ignore`.
 
 ## first_day_of_week
 
-The first day of the week (Monday or Sunday) used by `toStartOfInterval` and `date_diff` functions when using weeks as units.
+The first day of the week assumed by functions [`toStartOfInterval`](../../sql-reference/functions/date-time-functions.md#toStartOfInterval) and [`dateDiff`](../../sql-reference/functions/date-time-functions.md#dateDiff) functions when using weeks as unit.
 
 Possible values:
 

docs/en/sql-reference/functions/date-time-functions.md

@@ -1413,7 +1413,7 @@ toStartOfFifteenMinutes(toDateTime('2023-04-21 10:20:00')): 2023-04-21 10:15:00
 toStartOfFifteenMinutes(toDateTime('2023-04-21 10:23:00')): 2023-04-21 10:15:00
 ```
 
-## toStartOfInterval(date_or_date_with_time, INTERVAL x unit \[, time_zone\])
+## toStartOfInterval
 
 This function generalizes other `toStartOf*()` functions. For example,
 - `toStartOfInterval(t, INTERVAL 1 year)` returns the same as `toStartOfYear(t)`,
@@ -1440,7 +1440,7 @@ The calculation is performed relative to specific points in time:
 (*) hour intervals are special: the calculation is always performed relative to 00:00:00 (midnight) of the current day. As a result, only
     hour values between 1 and 23 are useful.
 
-If unit `week` was specified, `toStartOfInterval` assumes that weeks start on Monday by default. You can change this behavior with [`first_day_of_week`](/docs/en/operations/settings/settings.md/#first-day-of-week)
+If unit `week` was specified, `toStartOfInterval` assumes by default that weeks start on Monday. You can change this behavior with setting [`first_day_of_week`](../../operations/settings/settings.md/#first-day-of-week)
 
 **See Also**
 
@@ -1675,7 +1675,7 @@ Like [fromDaysSinceYearZero](#fromDaysSinceYearZero) but returns a [Date32](../.
 Returns the `unit` component of the difference between `startdate` and `enddate`. The difference is calculated using a precision of 1 nanosecond.
 E.g. the difference between `2021-12-29` and `2022-01-01` is 3 days for `day` unit, 0 months for `month` unit, 0 years for `year` unit.
 
-For an alternative to `age`, see function `date\_diff`.
+For an alternative to `age`, see function `date_diff`.
 
 **Syntax**
 
@@ -1749,9 +1749,9 @@ Result:
 Returns the count of the specified `unit` boundaries crossed between the `startdate` and the `enddate`.
 The difference is calculated using relative units, e.g. the difference between `2021-12-29` and `2022-01-01` is 3 days for unit `day` (see [toRelativeDayNum](#torelativedaynum)), 1 month for unit `month` (see [toRelativeMonthNum](#torelativemonthnum)) and 1 year for unit `year` (see [toRelativeYearNum](#torelativeyearnum)).
 
-If unit `week` was specified, `date\_diff` assumes that weeks start on Monday by default. You can change this behavior with [`first_day_of_week`](/docs/en/operations/settings/settings.md/#first-day-of-week)
+If unit `week` was specified, `date_diff` assumes by default that weeks start on Monday. You can change this behavior with setting [`first_day_of_week`](../../operations/settings/settings.md/#first-day-of-week)
 
-For an alternative to `date\_diff`, see function `age`.
+For an alternative to `date_diff`, see function `age`.
 
 **Syntax**
 

src/Core/Settings.h

@@ -549,6 +549,7 @@ class IColumn;
     M(Bool, formatdatetime_parsedatetime_m_is_month_name, true, "Formatter '%M' in functions 'formatDateTime()' and 'parseDateTime()' print/parse the month name instead of minutes.", 0) \
     M(Bool, parsedatetime_parse_without_leading_zeros, true, "Formatters '%c', '%l' and '%k' in function 'parseDateTime()' parse months and hours without leading zeros.", 0) \
     M(Bool, formatdatetime_format_without_leading_zeros, false, "Formatters '%c', '%l' and '%k' in function 'formatDateTime()' print months and hours without leading zeros.", 0) \
+    M(FirstDayOfWeek, first_day_of_week, FirstDayOfWeek::Monday, "The first day of the week (Monday or Sunday) used by date/time functions (default: Monday).", 0) \
     \
     M(UInt64, max_partitions_per_insert_block, 100, "Limit maximum number of partitions in single INSERTed block. Zero means unlimited. Throw exception if the block contains too many partitions. This setting is a safety threshold, because using large number of partitions is a common misconception.", 0) \
     M(Bool, throw_on_max_partitions_per_insert_block, true, "Used with max_partitions_per_insert_block. If true (default), an exception will be thrown when max_partitions_per_insert_block is reached. If false, details of the insert query reaching this limit with the number of partitions will be logged. This can be useful if you're trying to understand the impact on users when changing max_partitions_per_insert_block.", 0) \
@@ -1202,7 +1203,6 @@ class IColumn;
     M(Bool, precise_float_parsing, false, "Prefer more precise (but slower) float parsing algorithm", 0) \
     M(DateTimeOverflowBehavior, date_time_overflow_behavior, "ignore", "Overflow mode for Date, Date32, DateTime, DateTime64 types. Possible values: 'ignore', 'throw', 'saturate'.", 0) \
     M(Bool, validate_experimental_and_suspicious_types_inside_nested_types, true, "Validate usage of experimental and suspicious types inside nested types like Array/Map/Tuple", 0) \
-    M(FirstDayOfWeek, first_day_of_week, FirstDayOfWeek::Monday, "The first day of the week (Monday or Sunday) used by date/time functions (default: Monday).", 0) \
 
 
 // End of FORMAT_FACTORY_SETTINGS

src/Functions/FunctionsTimeWindow.h

@@ -46,7 +46,7 @@ struct ToStartOfTransform;
     {
         static auto execute(UInt32 t, UInt64 delta, const DateLUTImpl & time_zone)
         {
-            return time_zone.toStartOfWeekInterval(time_zone.toDayNum(t), delta, /*week_mode*/1);
+            return time_zone.toStartOfWeekInterval(time_zone.toDayNum(t), delta, /*week_mode*/ 1);
         }
     };
 

src/Functions/dateDiff.cpp

@@ -1,23 +1,25 @@
-
-#include <DataTypes/DataTypeDateTime.h>
-#include <DataTypes/DataTypeDateTime64.h>
-#include <DataTypes/DataTypesNumber.h>
-#include <Common/IntervalKind.h>
+#include <Columns/ColumnDecimal.h>
 #include <Columns/ColumnString.h>
 #include <Columns/ColumnsDateTime.h>
 #include <Columns/ColumnsNumber.h>
-#include <Columns/ColumnDecimal.h>
+#include <Common/IntervalKind.h>
 #include <Core/SettingsEnums.h>
+#include <DataTypes/DataTypeDateTime.h>
+#include <DataTypes/DataTypeDateTime64.h>
+#include <DataTypes/DataTypesNumber.h>
+#include <Functions/DateTimeTransforms.h>
 #include <Formats/FormatSettings.h>
 #include <Functions/IFunction.h>
 #include <Functions/FunctionHelpers.h>
 #include <Functions/FunctionFactory.h>
 #include <Functions/extractTimeZoneFromFunctionArguments.h>
-#include <Functions/DateTimeTransforms.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionHelpers.h>
+#include <Functions/IFunction.h>
 #include <Functions/TransformDateTime64.h>
-
-#include <Interpreters/Context.h>
+#include <Functions/extractTimeZoneFromFunctionArguments.h>
 #include <IO/WriteHelpers.h>
+#include <Interpreters/Context.h>
 
 #include <base/find_symbols.h>
 
@@ -173,10 +175,10 @@ public:
     template <typename TransformX, typename TransformY, typename T1, typename T2>
     Int64 calculate(const TransformX & transform_x, const TransformY & transform_y, T1 x, T2 y, const DateLUTImpl & timezone_x, const DateLUTImpl & timezone_y) const
     {
-        UInt8 week_mode = first_day_of_week == FirstDayOfWeek::Monday ? 0 : 3;
-
         if constexpr (is_diff)
         {
+            const UInt8 week_mode = (first_day_of_week == FirstDayOfWeek::Monday) ? 0 : 3;
+
             return static_cast<Int64>(transform_y.execute(y, timezone_y, week_mode))
                 - static_cast<Int64>(transform_x.execute(x, timezone_x, week_mode));
         }
@@ -322,7 +324,7 @@ public:
     }
 private:
     String name;
-    FirstDayOfWeek first_day_of_week;
+    const FirstDayOfWeek first_day_of_week;
 };
 
 
@@ -344,7 +346,7 @@ public:
     static FunctionPtr create(ContextPtr context) { return std::make_shared<FunctionDateDiff>(context); }
 
     explicit FunctionDateDiff(ContextPtr context)
-        : first_day_of_week(context->getSettingsRef().first_day_of_week)
+        : impl(name, context->getSettingsRef().first_day_of_week)
     {
     }
 
@@ -439,8 +441,7 @@ public:
         return res;
     }
 private:
-    FirstDayOfWeek first_day_of_week;
-    DateDiffImpl<is_relative> impl{name, first_day_of_week};
+    DateDiffImpl<is_relative> impl;
 };
 
 

src/Functions/toStartOfInterval.cpp

@@ -27,17 +27,14 @@ namespace ErrorCodes
 
 class FunctionToStartOfInterval : public IFunction
 {
-    FirstDayOfWeek first_day_of_week;
-
 public:
-    static FunctionPtr create(ContextPtr context) { return std::make_shared<FunctionToStartOfInterval>(context); }
+    static constexpr auto name = "toStartOfInterval";
 
+    static FunctionPtr create(ContextPtr context) { return std::make_shared<FunctionToStartOfInterval>(context); }
     explicit FunctionToStartOfInterval(ContextPtr context)
         : first_day_of_week(context->getSettingsRef().first_day_of_week)
     {
     }
-
-    static constexpr auto name = "toStartOfInterval";
     String getName() const override { return name; }
     bool isVariadic() const override { return true; }
     size_t getNumberOfArguments() const override { return 0; }
@@ -256,16 +253,16 @@ private:
         auto & result_data = col_to->getData();
         result_data.resize(size);
 
-        Int64 scale_multiplier = DecimalUtils::scaleMultiplier<DateTime64>(scale);
-        UInt8 week_mode = first_day_of_week == FirstDayOfWeek::Monday ? 1 : 0;
+        const Int64 scale_multiplier = DecimalUtils::scaleMultiplier<DateTime64>(scale);
+        const UInt8 week_mode = (first_day_of_week == FirstDayOfWeek::Monday) ? 1 : 0;
 
         for (size_t i = 0; i != size; ++i)
-        {
             result_data[i] = static_cast<ResultFieldType>(ToStartOfInterval<unit>::execute(time_data[i], num_units, scale_multiplier, week_mode, time_zone));
-        }
 
         return result_col;
     }
+
+    const FirstDayOfWeek first_day_of_week;
 };
 
 REGISTER_FUNCTION(ToStartOfInterval)

tests/queries/0_stateless/03005_first_day_of_week.sql

@@ -1,26 +1,28 @@
--- Testing setting behavior first_day_of_week.
--- It allows us to change `toStartOfInterval` and `date_diff` first day of week to Monday or Sunday
+-- Testing behavior of date/time functions under setting 'first_day_of_week'.
 
 SELECT '-- toStartOfInterval';
+
+-- default behavior
 SELECT
     toDateTime('2024-01-02 00:00:00', 'UTC') dt,
-    toStartOfInterval(dt, INTERVAL 1 WEEK) w_1, -- Monday, Jan 01
-    toStartOfInterval(dt, INTERVAL 2 WEEK) w_2 -- Monday, Dec 25
-;
+    toStartOfInterval(dt, INTERVAL 1 WEEK), -- Monday, Jan 01
+    toStartOfInterval(dt, INTERVAL 2 WEEK); -- Monday, Dec 25
 
 SELECT
     toDateTime('2024-01-02 00:00:00', 'UTC') dt,
-    toStartOfInterval(dt, INTERVAL 1 WEEK) w_1, -- Monday, Jan 01
-    toStartOfInterval(dt, INTERVAL 2 WEEK) w_2 -- Monday, Dec 25
+    toStartOfInterval(dt, INTERVAL 1 WEEK), -- Monday, Jan 01
+    toStartOfInterval(dt, INTERVAL 2 WEEK) -- Monday, Dec 25
 SETTINGS first_day_of_week = 'Monday';
 
 SELECT
     toDateTime('2024-01-02 00:00:00', 'UTC') dt,
-    toStartOfInterval(dt, INTERVAL 1 WEEK) w_1, -- Sunday, Dec 31
-    toStartOfInterval(dt, INTERVAL 2 WEEK) w_2 -- Sunday, Dec 24
+    toStartOfInterval(dt, INTERVAL 1 WEEK), -- Sunday, Dec 31
+    toStartOfInterval(dt, INTERVAL 2 WEEK) -- Sunday, Dec 24
 SETTINGS first_day_of_week = 'Sunday';
 
 SELECT '-- date_diff';
+
+-- default behavior
 SELECT
     toDateTime('2023-01-22 00:00:00', 'UTC') sunday,
     toDateTime('2023-01-23 00:00:00', 'UTC') monday,
@@ -29,8 +31,7 @@ SELECT
     dateDiff('week', sunday, monday),
     age('week', monday, tuesday),
     age('week', sunday, monday),
-    age('week', sunday, monday + toIntervalDay(10))
-;
+    age('week', sunday, monday + toIntervalDay(10));
 
 SELECT
     toDateTime('2023-01-22 00:00:00', 'UTC') sunday,