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/**
* Tests for the $$REMOVE system variable.
*/
(function() {
"use strict";
let coll = db[jsTest.name()];
coll.drop();
assert.commandWorked(coll.insert({_id: 1, a: 2, b: 3}));
assert.commandWorked(coll.insert({_id: 2, a: 3, b: 4}));
assert.commandWorked(coll.insert({_id: 3, a: {b: 98, c: 99}}));
let projectStage = {
$project: {_id: 0, a: 1, b: {$cond: {if: {$eq: ["$b", 4]}, then: "$$REMOVE", else: "$b"}}}
};
// Test that we can conditionally remove a field in $project.
assert.eq([{a: 2, b: 3}], coll.aggregate([{$match: {_id: 1}}, projectStage]).toArray());
assert.eq([{a: 3}], coll.aggregate([{$match: {_id: 2}}, projectStage]).toArray());
// Test removal of a nested field, using $project.
assert.eq([{a: {b: 98}}],
coll.aggregate([{$match: {_id: 3}}, {$project: {_id: 0, "a.b": 1}}]).toArray());
assert.eq([{a: {}}],
coll.aggregate([{$match: {_id: 3}}, {$project: {_id: 0, "a.b": "$$REMOVE"}}]).toArray());
assert.eq([{a: {}}],
coll.aggregate([{$match: {_id: 3}}, {$project: {_id: 0, a: {b: "$$REMOVE"}}}]).toArray());
// Test removal of a nested field, using $addFields.
assert.eq([{_id: 3, a: {c: 99}}],
coll.aggregate([{$match: {_id: 3}}, {$addFields: {"a.b": "$$REMOVE"}}]).toArray());
// Test that any field path following "$$REMOVE" also evaluates to missing.
assert.eq([{_id: 3}],
coll.aggregate([{$match: {_id: 3}}, {$addFields: {"a": "$$REMOVE.a.c"}}]).toArray());
// Test that $$REMOVE can be used together with user-defined variables in a $let.
assert.eq(
[{a: {b: 3, d: 4}}],
coll.aggregate([
{$match: {_id: 3}},
{
$project: {
_id: 0,
a: {
$let: {vars: {bar: 3, foo: 4}, in : {b: "$$bar", c: "$$REMOVE", d: "$$foo"}}
}
}
}
])
.toArray());
// Test that $$REMOVE cannot be assigned in a $let.
assert.commandFailedWithCode(db.runCommand({
aggregate: coll.getName(),
cursor: {},
pipeline: [
{$match: {_id: 3}},
{$project: {_id: 0, a: {$let: {vars: {"REMOVE": 3}, in : {b: "$$REMOVE", c: 2}}}}}
]
}),
16867);
// Test that $$REMOVE, $$CURRENT, $$ROOT, and user-defined variables can all be used together.
assert.eq(
[{a: {b: 3, d: {_id: 1, a: 2, b: 3}, e: {_id: 1, a: 2, b: 3}}}],
coll.aggregate([
{$match: {_id: 1}},
{
$project: {
_id: 0,
a: {
$let: {
vars: {myVar: 3},
in : {b: "$$myVar", c: "$$REMOVE", d: "$$ROOT", e: "$$CURRENT"}
}
}
}
}
])
.toArray());
}());
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