Fix behaviour of DATEDIFF() and DATEDIFF_BIG() functions for week and quarter dateparts

[Anikait143]

Description

1. Issues

• DATEDIFF() and DATEDIFF_BIG() functions return incorrect results when using 'week' and 'quarter' as datepart unit.
• DATEDIFF_BIG() function gives wrong error message in case of overflow.

2. Changes made to fix the issues

• Fix calculation logic for considering a week if a Saturday-Sunday boundaries crossed.
• Fix calculation logic for considering a quarter if a quarter boundary crossed.
  1. March-April
  2. June-July
  3. September-October
  4. December-January
• Fix error message for DATEDIFF_BIG() function in case of overflow.

# Input
1> declare @runForDate datetime = '01/22/2012';
2> declare @evaluationDate datetime = DATEADD(DAY,-1,@runForDate);
3> select DATEDIFF(wk,7,@evaluationDate)
4> go

# previous output (wrong output)               
datediff   
-----------
       5846

# current output (correct output)
datediff   
-----------
       5845                                                                                                                                                                                                                                                      

(1 rows affected)

# previous output (wrong output)
1> select DATEDIFF(quarter, '1999-12-31', '2000-01-01') AS Quarters
2> go
Quarters   
-----------
          0  

# current output (correct output)
1> select DATEDIFF(quarter, '1999-12-31', '2000-01-01') AS Quarters
2> go
Quarters   
-----------
          1

• Added Test Cases for these issues

Task: BABEL- 5461, BABEL-5503
Authored-by: Anikait Agrawal [email protected]
Signed-off-by: Anikait Agrawal [email protected]

Test Scenarios Covered

• Use case based - YES

• Boundary conditions - YES

• Arbitrary inputs - YES

• Negative test cases - YES

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Memory tests -

• Client tests -

Check List

• Commits are signed per the DCO using --signoff

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[coveralls]

Pull Request Test Coverage Report for Build 12629578069

Details

• 43 of 43 (100.0%) changed or added relevant lines in 1 file are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.007%) to 74.874%

---

Files with Coverage Reduction	New Missed Lines	%
contrib/babelfishpg_tds/src/backend/tds/tdsutils.c	1	73.66%
contrib/babelfishpg_tds/src/backend/tds/tdscomm.c	2	76.03%

Totals
Change from base Build 12596818602:	0.007%
Covered Lines:	46626
Relevant Lines:	62273

---

💛 - Coveralls

[jsudrik]

Approved.