Fix Datapart functions to be Timezone Invariant

[shah-nirmit]

Description

We were incorrectly passing timezone to timestamp2tm function which would cause the datepart functions to be timezone dependent , If we pass tzp by reference to timestamp2tm function, then internally localtime converts the given original timestamp value to date and time values adding timezone offset taking GMT as a reference timezone. However, if NULL is passed instead then we keep the original timestamp intact and that's what actually PG does.

Cherry-pick #3226

Issues Resolved

BABEL-5453

Signed-off-by: Nirmit Shah nirmisha@amazon.com

Test Scenarios Covered

• Use case based - YES

• Boundary conditions - YES

• Arbitrary inputs -

• Negative test cases -

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Client tests -

Check List

• Commits are signed per the DCO using --signoff

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[coveralls]

Pull Request Test Coverage Report for Build 12313409976

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 73.811%

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Totals
Change from base Build 12278092653:	0.0%
Covered Lines:	43162
Relevant Lines:	58476

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💛 - Coveralls