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// In SERVER-17258, the $reduce expression was introduced. In this test file, we check the
// functionality and error cases of the expression.
load("jstests/aggregation/extras/utils.js"); // For assertErrorCode and testExpression.
(function() {
"use strict";
var coll = db.reduce;
testExpression(
coll,
{
$reduce:
{input: [1, 2, 3], initialValue: {$literal: 0}, in : {$sum: ["$$this", "$$value"]}}
},
6);
testExpression(coll, {$reduce: {input: [], initialValue: {$literal: 0}, in : 10}}, 0);
testExpression(
coll,
{
$reduce:
{input: [1, 2, 3], initialValue: [], in : {$concatArrays: ["$$value", ["$$this"]]}}
},
[1, 2, 3]);
testExpression(coll,
{
$reduce: {
input: [1, 2],
initialValue: [],
in : {$concatArrays: ["$$value", ["$$value.notAField"]]}
}
},
[[], []]);
// A nested $reduce which sums each subarray, then multiplies the results.
testExpression(coll,
{
$reduce: {
input: [[1, 2, 3], [4, 5]],
initialValue: 1,
in : {
$multiply: [
"$$value",
{
$reduce: {
input: "$$this",
initialValue: 0,
in : {$sum: ["$$value", "$$this"]}
}
}
]
}
}
},
54);
// A nested $reduce using a $let to allow the inner $reduce to access the variables of the
// outer.
testExpression(coll,
{
$reduce: {
input: [[0, 1], [2, 3]],
initialValue: {allElements: [], sumOfInner: {$literal: 0}},
in : {
$let: {
vars: {outerValue: "$$value", innerArray: "$$this"},
in : {
$reduce: {
input: "$$innerArray",
initialValue: "$$outerValue",
in : {
allElements: {
$concatArrays:
["$$value.allElements", ["$$this"]]
},
sumOfInner:
{$sum: ["$$value.sumOfInner", "$$this"]}
}
}
}
}
}
}
},
{allElements: [0, 1, 2, 3], sumOfInner: 6});
// Nullish input produces null as an output.
testExpression(coll, {$reduce: {input: null, initialValue: {$literal: 0}, in : 5}}, null);
testExpression(
coll, {$reduce: {input: "$nonexistent", initialValue: {$literal: 0}, in : 5}}, null);
// Error cases for $reduce.
// $reduce requires an object.
var pipeline = {$project: {reduced: {$reduce: 0}}};
assertErrorCode(coll, pipeline, 40075);
// Unknown field specified.
pipeline = {
$project: {
reduced: {
$reduce: {
input: {$literal: 0},
initialValue: {$literal: 0},
in : {$literal: 0},
notAField: {$literal: 0}
}
}
}
};
assertErrorCode(coll, pipeline, 40076);
// $reduce requires input to be specified.
pipeline = {$project: {reduced: {$reduce: {initialValue: {$literal: 0}, in : {$literal: 0}}}}};
assertErrorCode(coll, pipeline, 40077);
// $reduce requires initialValue to be specified.
pipeline = {$project: {reduced: {$reduce: {input: {$literal: 0}, in : {$literal: 0}}}}};
assertErrorCode(coll, pipeline, 40078);
// $reduce requires in to be specified.
pipeline = {
$project: {reduced: {$reduce: {input: {$literal: 0}, initialValue: {$literal: 0}}}}
};
assertErrorCode(coll, pipeline, 40079);
// $$value is undefined in the non-'in' arguments of $reduce.
pipeline = {$project: {reduced: {$reduce: {input: "$$value", initialValue: [], in : []}}}};
assertErrorCode(coll, pipeline, 17276);
// $$this is undefined in the non-'in' arguments of $reduce.
pipeline = {$project: {reduced: {$reduce: {input: "$$this", initialValue: [], in : []}}}};
assertErrorCode(coll, pipeline, 17276);
}());
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