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// SERVER-20168: Add option to $unwind to output a null result for empty arrays.
(function() {
"use strict";
var coll = db.server20168;
coll.drop();
// Should return no results on a non-existent collection.
var results = coll.aggregate([{$unwind: {path: "$x"}}]).toArray();
assert.eq(0, results.length, "$unwind returned the wrong number of results");
/**
* Asserts that with the input 'inputDoc', an $unwind stage on 'unwindPath' should produce no
* results if preserveNullAndEmptyArrays is not specified, and produces one result, equal to
* 'outputDoc', if it is specified.
*/
function testPreserveNullAndEmptyArraysParam(inputDoc, unwindPath, outputDoc) {
coll.drop();
assert.writeOK(coll.insert(inputDoc));
// If preserveNullAndEmptyArrays is passed, we should get an output document.
var preservedResults =
coll.aggregate([{$unwind: {path: unwindPath, preserveNullAndEmptyArrays: true}}])
.toArray();
assert.eq(1, preservedResults.length, "$unwind returned the wrong number of results");
assert.eq(preservedResults[0],
outputDoc,
"Unexpected result for an $unwind with preserveNullAndEmptyArrays " +
"(input was " + tojson(inputDoc) + ")");
// If not, we should get no outputs.
var defaultResults = coll.aggregate([{$unwind: {path: unwindPath}}]).toArray();
assert.eq(0, defaultResults.length, "$unwind returned the wrong number of results");
}
testPreserveNullAndEmptyArraysParam({_id: 0}, "$x", {_id: 0});
testPreserveNullAndEmptyArraysParam({_id: 0, x: null}, "$x", {_id: 0, x: null});
testPreserveNullAndEmptyArraysParam({_id: 0, x: []}, "$x", {_id: 0});
}());
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