fix(sum): returns 0 when is empty matching

[t-bonatti]

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Description of change

Fix #6299

[codecov]

Codecov Report

Merging #9984 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #9984      +/-   ##
==========================================
+ Coverage   96.38%   96.39%   +<.01%     
==========================================
  Files          63       63              
  Lines        9389     9395       +6     
==========================================
+ Hits         9050     9056       +6     
  Misses        339      339

Impacted Files	Coverage Δ
lib/model.js	96.67% <100%> (ø)	⬆️
lib/query-interface.js	91.13% <100%> (+0.02%)	⬆️
lib/dialects/postgres/data-types.js	97.81% <0%> (-0.08%)	⬇️
lib/dialects/sqlite/query-generator.js	96.44% <0%> (-0.04%)	⬇️
lib/operators.js	100% <0%> (ø)	⬆️
lib/dialects/abstract/query-generator/operators.js	90.9% <0%> (ø)	⬆️
lib/dialects/abstract/query-generator.js	97.65% <0%> (+0.01%)	⬆️
lib/dialects/sqlite/data-types.js	97.05% <0%> (+0.18%)	⬆️

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[t-bonatti]

@sushantdhiman Could you take a look at this fix too?

[sushantdhiman]

sum should return 0 not null as number is expected for this method. It should be solved at Model.aggregate level rather than query-interface level.

[t-bonatti]

@sushantdhiman

I changed to return 0.
I returned null before because the Postgres do that.

[t-bonatti]

I kept this change to not return NaN

[sushantdhiman]

👍

[sushantdhiman]

Thanks @t-bonatti

I returned null before because the Postgres do that.

Correct behaviour if we want to know if record exists as per our condition, but I can't say other dialect adheres to this. We can simply return numerical values from aggregate for now

[mariomixtega]

Is this already on 4.42.0?

[holm]

I am just upgrading to Sequelize 5, and this caught me by surprise. It seems very strange that this method now returns 0 if the result is null. This seems to assume that the result of an aggregation is a number. This is not at all the case in general. It can really be any datatype, and by returning 0 as a default, this breaks the expected type. In our case we are using it to find the max of a date field.