Fix for DATENAME() gives incorrect value with TZOFFSET part

[manisha-deshpande]

Description

Currently, DATENAME function returns a numeric value for TZOFFSET datepart, which does not match SQL Server's text output.

Root cause: The function definition of sys.datename explicitly calls the DATEPART function for most argument values, including TZOFFSET, thereby returning a numerical offset value instead of the required text format (+/-HH:MM).

Fix: Modified the sys function's SQL definition to extract and return the timezone offset substring from the input - similar to how the offset_string is determined in DATETRUNC/DATEBUCKET - if the argument matches tzoffset. Furthermore, translated the function from SQL language to plpgsql in order to enable raising an exception for unsupported input datetime datatypes such as date, time, datetime and smalldatetime.

Additional changes: Updated an existing jdbc test case datepart-vu-verify.sql to avoid 'failing' table insertions of DATENAME(TZOFFSET, cursor(date)) for incompatible date types: datetime, smalldatetime, datetimeoffset.

IF NOT (@datepart = 'tzoffset' AND @datatype NOT IN ('DATETIMEOFFSET', 'DATETIME2'))
Added corresponding version upgrade tests.

Issues Resolved

BABEL-5846

Test Scenarios Covered

• Use case based -

-- Test positive/negative offsets
SELECT DATENAME(TZOFFSET, '2025-06-03 14:30:15 +01:59');
GO
~~START~~
text
+01:59
~~END~~

select datename(TZoffset, CAST('2016-12-26 23:30:05.523456+8'AS datetimeoffset));
GO
~~START~~
text
+08:00
~~END~~

SELECT DATENAME(TZOFFSET, CAST('2025-06-03 14:30:15 +01:59' AS DATETIMEOFFSET));
GO
~~START~~
text
+01:59
~~END~~

SELECT DATENAME(TZOFFSET, CAST('2025-06-03 14:30:15 -01:59' AS DATETIMEOFFSET));
GO
~~START~~
text
-01:59
~~END~~

• Boundary conditions -

-- Test case for NULL input
SELECT DATENAME(TZOFFSET, NULL);
GO
~~START~~
text
<NULL>
~~END~~

-- Test case for empty string
SELECT DATENAME(TZOFFSET, '');
GO
~~START~~
text
+00:00
~~END~~

-- Boundary values
SELECT DATENAME(TZOFFSET, CAST('2025-06-03 14:30:15 +14:00' AS DATETIMEOFFSET));
GO
~~START~~
text
+14:00
~~END~~

SELECT DATENAME(TZOFFSET, CAST('2025-06-03 14:30:15 -14:00' AS DATETIMEOFFSET));
GO
~~START~~
text
-14:00
~~END~~

-- Supported date time datatype inputs
SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15' AS DATETIME2)) AS datetime2_type;
GO
~~START~~
text
+00:00
~~END~~

SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15' AS DATETIMEOFFSET)) AS datetimeoffset_type;
GO
~~START~~
text
+00:00
~~END~~

• Arbitrary inputs -

    -- Invalid date time inputs
SELECT DATENAME(TZOFFSET, '2025-06-0314:30:15+01:59');
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: Conversion failed when converting date and/or time from character string.)~~

-- Test date inputs without offset specified
SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15.1234567' AS DATETIMEOFFSET));
GO
~~START~~
text
+00:00
~~END~~

SELECT datename(TZOFFSET, CAST('2025-06-03' AS DATETIMEOFFSET));
GO
~~START~~
text
+00:00
~~END~~

SELECT datename(TZOFFSET, CAST('14:30:15.1234567' AS DATETIMEOFFSET));
GO
~~START~~
text
+00:00
~~END~~

SELECT datename(TZOFFSET, CAST('' AS DATETIMEOFFSET));
GO
~~START~~
text
+00:00
~~END~~

• Negative test cases -

-- Error Scenarios
    -- Unsupported date time datatype inputs
SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15 +01:30' AS DATE)) AS date_type;
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: The datepart tzoffset is not supported by date function datename for data type date.)~~


SELECT datename(TZOFFSET, CAST('14:30:15' AS TIME)) AS time_type;
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: The datepart tzoffset is not supported by date function datename for data type time without time zone.)~~


SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15' AS DATETIME)) AS datetime_type;
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: The datepart tzoffset is not supported by date function datename for data type datetime.)~~


SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15' AS SMALLDATETIME)) AS smalldatetime_type;
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: The datepart tzoffset is not supported by date function datename for data type smalldatetime.)~~



    -- Invalid date time inputs
SELECT datename(TZOFFSET, CAST('2025-06-0314:30:15+130' AS DATETIMEOFFSET));
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: invalid input syntax for type datetimeoffset: "2025-06-0314:30:15+130")~~


SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15 -16:00' AS DATETIMEOFFSET));
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: time zone displacement out of range: "2025-06-03 14:30:15 -16:00")~~


SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15 +10:60' AS DATETIMEOFFSET));
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: time zone displacement out of range: "2025-06-03 14:30:15 +10:60")~~


SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15 +01:30' AS DATETIMEOFFSET) AT TIME ZONE 'Invalid Time Zone');
GO
~~START~~
text
~~ERROR (Code: 33557097)~~

~~ERROR (Message: Argument data type or the parameter Invalid Time Zone provided to AT TIME ZONE clause is invalid.)~~


SELECT datename(TZOFFSET, SWITCHOFFSET(CAST('2025-06-03 14:30:15 +01:30' AS DATETIMEOFFSET), 'Invalid Offset'));
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: The timezone provided to builtin function todatetimeoffset is invalid.)~~


SELECT datename(TZOFFSET, TODATETIMEOFFSET(CAST('2025-06-03 14:30:15' AS DATETIME2), 'Invalid Offset'));
GO
~~ERROR (Code: 33557097)~~

~~ERROR (Message: The timezone provided to builtin function todatetimeoffset is invalid.)~~

• Integration test cases -

-- Test with other functions
SELECT datename(TZOFFSET, CAST('2025-06-03 14:30:15 +01:30' AS DATETIMEOFFSET) AT TIME ZONE 'Pacific Standard Time');
GO
~~START~~
text
-07:00
~~END~~

SELECT DATENAME(TZOFFSET, SWITCHOFFSET(CAST('2025-06-03 14:30:15 +01:30' AS DATETIMEOFFSET), '-08:00'));
GO
~~START~~
text
-08:00
~~END~~

SELECT DATENAME(TZOFFSET, TODATETIMEOFFSET(CAST('2025-06-03 14:30:15' AS DATETIME2), '-03:30'));
GO
~~START~~
text
-03:30
~~END~~

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Client tests -

Check List

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[coveralls]

Pull Request Test Coverage Report for Build 16008532369

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 75.87%

---

Totals
Change from base Build 16001000140:	0.003%
Covered Lines:	49472
Relevant Lines:	65206

---

💛 - Coveralls

[manisha-deshpande]

TODO: Will look into version upgrade test failures
Edit: DONE

[manisha-deshpande]

Updating the DATENAME function from STABLE to IMMUTABLE fails an existing test case BABEL_1475 due to disallowing the use of computed columns with DATENAME:

--- /home/runner/work/babelfish_extensions/babelfish_extensions/test/JDBC/./expected/BABEL-1475-vu-prepare.out	2025-06-27 21:14:12.077114693 +0000
+++ /home/runner/work/babelfish_extensions/babelfish_extensions/test/JDBC/./output/BABEL-1475-vu-prepare.out	2025-06-27 21:29:59.986827039 +0000
@@ -44,7 +44,9 @@
 CREATE TABLE BABEL_1475_vu_prepare_datename (dt date, year as DATENAME(year, dt), month as DATENAME(month, dt), weekday as DATENAME(dow, dt), dayofyear as DATENAME(dayofyear, dt), day as DATENAME(day, dt));
 INSERT INTO BABEL_1475_vu_prepare_datename (dt) values ('1912-10-25');
 GO
-~~ROW COUNT: 1~~
+~~ERROR (Code: 33557097)~~
+
+~~ERROR (Message: generation expression is not immutable)~~
 -- Test DATEPART function for computed columns
--- /home/runner/work/babelfish_extensions/babelfish_extensions/test/JDBC/./expected/BABEL-1475-vu-verify.out	2025-06-27 21:14:12.077114693 +0000
+++ /home/runner/work/babelfish_extensions/babelfish_extensions/test/JDBC/./output/BABEL-1475-vu-verify.out	2025-06-27 21:30:00.017827323 +0000
@@ -55,10 +55,9 @@
 -- Test DATENAME function for computed columns
 SELECT year, month, weekday, dayofyear, day from BABEL_1475_vu_prepare_datename;
 GO
-~~START~~
-text#!#text#!#text#!#text#!#text
-1912#!#October#!#Friday#!#299#!#25
-~~END~~
+~~ERROR (Code: 33557097)~~
+
+~~ERROR (Message: relation "babel_1475_vu_prepare_datename" does not exist)~~

cc: @KushaalShroff @Anikait143

[KushaalShroff]

Please check Test failures!