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/**
* Tests the 'n' family of accumulators implemented as expressions.
*/
(function() {
'use strict';
const coll = db[jsTestName()];
const doc = {
a: [1, 2, 3, 5, 7, 9],
n: 4,
diff: 2
};
const isExactTopNEnabled = db.adminCommand({getParameter: 1, featureFlagExactTopNAccumulator: 1})
.featureFlagExactTopNAccumulator.value;
if (!isExactTopNEnabled) {
// Verify that $minN/$maxN cannot be used if the feature flag is set to false and ignore the
// rest of the test.
assert.commandFailedWithCode(
coll.runCommand(
"aggregate",
{pipeline: [{$project: {output: {'$minN': {n: 3, input: [3, 1, 2, 3]}}}}], cursor: {}}),
31325);
return;
}
coll.drop();
assert.commandWorked(coll.insert(doc));
function testExpr(expression, expected) {
assert.eq(coll.aggregate([{$project: {_id: 0, output: expression}}]).toArray()[0].output,
expected);
}
let args = {n: 3, input: [5, 4, 3, 2, 1]};
testExpr({$minN: args}, [1, 2, 3]);
testExpr({$maxN: args}, [5, 4, 3]);
testExpr({$firstN: args}, [5, 4, 3]);
testExpr({$lastN: args}, [3, 2, 1]);
args = {
n: 3,
input: [null, 2, null, 1]
};
testExpr({$minN: args}, [1, 2]);
testExpr({$maxN: args}, [2, 1]);
testExpr({$firstN: args}, [null, 2, null]);
testExpr({$lastN: args}, [2, null, 1]);
args = {
n: 3,
input: "$a"
};
testExpr({$minN: args}, [1, 2, 3]);
testExpr({$maxN: args}, [9, 7, 5]);
testExpr({$firstN: args}, [1, 2, 3]);
testExpr({$lastN: args}, [5, 7, 9]);
args = {
n: "$n",
input: "$a"
};
testExpr({$minN: args}, [1, 2, 3, 5]);
testExpr({$maxN: args}, [9, 7, 5, 3]);
testExpr({$firstN: args}, [1, 2, 3, 5]);
testExpr({$lastN: args}, [3, 5, 7, 9]);
args = {
n: {$subtract: ["$n", "$diff"]},
input: [3, 4, 5]
};
testExpr({$minN: args}, [3, 4]);
testExpr({$maxN: args}, [5, 4]);
testExpr({$firstN: args}, [3, 4]);
testExpr({$lastN: args}, [4, 5]);
})();
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