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Assigned Teams:

Query Optimization
Operating System:
ALL
Steps To Reproduce:

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db.test.drop();

db.test.insert({_id: 1, x: new Date()});

// Returns a result.
db.test.aggregate([{$project: {a: {$add: [null, new Date(), "$x"]}}}])

// Fails with error code 16612, "only one date allowed in an $add expression".
db.test.aggregate([{$project: {a: {$add: [new Date(), "$x", null]}}}])

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db.test.drop(); db.test.insert({_id: 1, x: new Date()}); // Returns a result. db.test.aggregate([{$project: {a: {$add: [null, new Date(), "$x"] }}}]) // Fails with error code 16612, "only one date allowed in an $add expression". db.test.aggregate([{$project: {a: {$add: [new Date(), "$x", null] }}}])
Linked BF Score:
53

The $add expression is defined as being commutative, which is not true when a null value exists in the list being summed.

duplicates

SERVER-63099 Constant folding should not assume arithmetic is associative or commutative in the general case

Participants:: [DO NOT USE] Backlog - Query Optimization, Davis Haupt, James Wahlin