Add index on task table

[GDay]

Fixes #160

[coveralls]

Pull Request Test Coverage Report for Build 10755987978

Details

• 6 of 6 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 89.689%

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Totals
Change from base Build 10755873622:	0.02%
Covered Lines:	3375
Relevant Lines:	3763

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💛 - Coveralls