feat: add docs and tests

docs/en/sql-reference/functions/type-conversion-functions.md

@@ -1339,3 +1339,147 @@ Result:
 │ 2,"good"                                  │
 └───────────────────────────────────────────┘
 ```
+
+## snowflakeToDateTime {#snowflakeToDateTime}
+
+extract time from snowflake id as DateTime format.
+
+**Syntax**
+
+``` sql
+snowflakeToDateTime(value [, time_zone])
+```
+
+**Parameters**
+
+-   `value` — `snowflake id`, Int64 value.
+-   `time_zone` — [Timezone](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-timezone). The function parses `time_string` according to the timezone. Optional. [String](../../sql-reference/data-types/string.md).
+
+**Returned value**
+
+-  value converted to the `DateTime` data type.
+
+**Example**
+
+Query:
+
+``` sql
+SELECT snowflakeToDateTime(CAST('1426860702823350272', 'Int64'), 'UTC');
+```
+
+Result:
+
+``` text
+
+┌─snowflakeToDateTime(CAST('1426860702823350272', 'Int64'), 'UTC')─┐
+│                                              2021-08-15 10:57:56 │
+└──────────────────────────────────────────────────────────────────┘
+```
+
+## snowflakeToDateTime64 {#snowflakeToDateTime64}
+
+extract time from snowflake id as DateTime64 format.
+
+**Syntax**
+
+``` sql
+snowflakeToDateTime64(value [, time_zone])
+```
+
+**Parameters**
+
+-   `value` — `snowflake id`, Int64 value.
+-   `time_zone` — [Timezone](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-timezone). The function parses `time_string` according to the timezone. Optional. [String](../../sql-reference/data-types/string.md).
+
+**Returned value**
+
+-  value converted to the `DateTime64` data type.
+
+**Example**
+
+Query:
+
+``` sql
+SELECT snowflakeToDateTime64(CAST('1426860802823350272', 'Int64'), 'UTC');
+```
+
+Result:
+
+``` text
+
+┌─snowflakeToDateTime64(CAST('1426860802823350272', 'Int64'), 'UTC')─┐
+│                                            2021-08-15 10:58:19.841 │
+└────────────────────────────────────────────────────────────────────┘
+```
+
+## dateTimeToSnowflake {#dateTimeToSnowflake}
+
+convert DateTime to the first snowflake id at the giving time.
+
+**Syntax**
+
+``` sql
+dateTimeToSnowflake(value)
+```
+
+**Parameters**
+
+-   `value` — Date and time. [DateTime](../../sql-reference/data-types/datetime.md).
+
+
+**Returned value**
+
+-   `value` converted to the `Int64` data type as the first snowflake id at that time.
+
+**Example**
+
+Query:
+
+``` sql
+SELECT dateTimeToSnowflake(CAST('2021-08-15 18:57:56', 'DateTime'));
+```
+
+Result:
+
+``` text
+
+┌─dateTimeToSnowflake(CAST('2021-08-15 18:57:56', 'DateTime'))─┐
+│                                          1426860702823350272 │
+└──────────────────────────────────────────────────────────────┘
+```
+
+
+## dateTime64ToSnowflake {#dateTime64ToSnowflake}
+
+convert DateTime64 to the first snowflake id at the giving time.
+
+**Syntax**
+
+``` sql
+dateTime64ToSnowflake(value)
+```
+
+**Parameters**
+
+-   `value` — Date and time. [DateTime64](../../sql-reference/data-types/datetime64.md).
+
+
+**Returned value**
+
+-   `value` converted to the `Int64` data type as the first snowflake id at that time.
+
+**Example**
+
+Query:
+
+``` sql
+SELECT dateTime64ToSnowflake(CAST('2021-08-15 18:57:56.073', 'DateTime64'));
+```
+
+Result:
+
+``` text
+┌─dateTime64ToSnowflake(CAST('2021-08-15 18:57:56.073', 'DateTime64'))─┐
+│                                                  1426860703129534464 │
+└──────────────────────────────────────────────────────────────────────┘
+```

tests/queries/0_stateless/01942_dateTimeToSnowflake.reference

@@ -0,0 +1,6 @@
+const column
+2021-08-15 18:57:56	1426860702823350272
+2021-08-15 18:57:56.492	1426860704886947840
+non-const column
+2021-08-15 18:57:56	1426860702823350272
+2021-08-15 18:57:56.492	1426860704886947840

tests/queries/0_stateless/01942_dateTimeToSnowflake.sql

@@ -0,0 +1,23 @@
+-- Error cases
+SELECT dateTimeToSnowflake();  -- {serverError 42}
+SELECT dateTime64ToSnowflake();  -- {serverError 42}
+
+SELECT dateTimeToSnowflake('abc');  -- {serverError 43}
+SELECT dateTime64ToSnowflake('abc');  -- {serverError 43}
+
+SELECT dateTimeToSnowflake('abc', 123);  -- {serverError 42}
+SELECT dateTime64ToSnowflake('abc', 123);  -- {serverError 42}
+
+SELECT 'const column';
+WITH toDateTime('2021-08-15 18:57:56') AS dt
+SELECT dt, dateTimeToSnowflake(dt);
+
+WITH toDateTime64('2021-08-15 18:57:56.492', 3) AS dt64
+SELECT dt64, dateTime64ToSnowflake(dt64);
+
+SELECT 'non-const column';
+WITH toDateTime('2021-08-15 18:57:56') AS x
+SELECT materialize(x) as dt, dateTimeToSnowflake(dt);;
+
+WITH toDateTime64('2021-08-15 18:57:56.492', 3) AS x
+SELECT materialize(x) as dt64, dateTime64ToSnowflake(dt64);

tests/queries/0_stateless/01942_snowflakeToDateTime.reference

@@ -0,0 +1,3 @@
+const column
+UTC	1426860704886947840	2021-08-15 10:57:56	DateTime(\'UTC\')	2021-08-15 10:57:56.492	DateTime64(3, \'UTC\')
+Asia/Shanghai	1426860704886947840	2021-08-15 18:57:56	DateTime(\'Asia/Shanghai\')	2021-08-15 18:57:56.492	DateTime64(3, \'Asia/Shanghai\')

tests/queries/0_stateless/01942_snowflakeToDateTime.sql

@@ -0,0 +1,32 @@
+-- -- Error cases
+SELECT snowflakeToDateTime();  -- {serverError 42}
+SELECT snowflakeToDateTime64();  -- {serverError 42}
+
+SELECT snowflakeToDateTime('abc');  -- {serverError 43}
+SELECT snowflakeToDateTime64('abc');  -- {serverError 43}
+
+SELECT snowflakeToDateTime('abc', 123);  -- {serverError 43}
+SELECT snowflakeToDateTime64('abc', 123);  -- {serverError 43}
+
+SELECT 'const column';
+WITH
+	CAST(1426860704886947840 AS Int64) AS i64,
+	'UTC' AS tz
+SELECT
+	tz,
+	i64,
+	snowflakeToDateTime(i64, tz) as dt,
+	toTypeName(dt),
+	snowflakeToDateTime64(i64, tz) as dt64,
+	toTypeName(dt64);
+
+WITH
+	CAST(1426860704886947840 AS Int64) AS i64,
+	'Asia/Shanghai' AS tz
+SELECT
+	tz,
+	i64,
+	snowflakeToDateTime(i64, tz) as dt,
+	toTypeName(dt),
+	snowflakeToDateTime64(i64, tz) as dt64,
+	toTypeName(dt64);