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// Tests the behaviour of the $merge stage with whenMatched=merge and whenNotMatched=discard.
//
// Cannot implicitly shard accessed collections because a collection can be implictly created and
// exists when none is expected.
(function() {
"use strict";
load("jstests/aggregation/extras/merge_helpers.js"); // For dropWithoutImplicitRecreate.
load("jstests/aggregation/extras/utils.js"); // For assertArrayEq.
load("jstests/libs/fixture_helpers.js"); // For FixtureHelpers.isSharded.
const source = db[`${jsTest.name()}_source`];
source.drop();
const target = db[`${jsTest.name()}_target`];
target.drop();
const mergeStage = {
$merge: {into: target.getName(), whenMatched: "merge", whenNotMatched: "discard"}
};
const pipeline = [mergeStage];
// Test $merge when some documents in the source collection don't have a matching document in
// the target collection. The merge operation should succeed and unmatched documents discarded.
(function testMergeIfMatchingDocumentNotFound() {
// Single document without a match.
assert.commandWorked(source.insert([{_id: 1, a: 1}, {_id: 2, a: 2}, {_id: 3, a: 3}]));
assert.commandWorked(target.insert([{_id: 1, b: 1}, {_id: 3, b: 3}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq(
{actual: target.find().toArray(), expected: [{_id: 1, a: 1, b: 1}, {_id: 3, a: 3, b: 3}]});
// Multiple documents without a match.
assert(target.drop());
assert.commandWorked(target.insert([{_id: 1, b: 1}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({actual: target.find().toArray(), expected: [{_id: 1, a: 1, b: 1}]});
})();
// Test $merge when all documents in the source collection have a matching document in the
// target collection.
(function testMergeWhenAllDocumentsHaveMatch() {
// Source has a single element with a match in the target.
assert(source.drop());
assert(target.drop());
assert.commandWorked(source.insert({_id: 3, a: 3}));
assert.commandWorked(target.insert([{_id: 1, b: 1}, {_id: 3, b: 3}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq(
{actual: target.find().toArray(), expected: [{_id: 1, b: 1}, {_id: 3, a: 3, b: 3}]});
// Source has multiple documents with matches in the target.
assert(source.drop());
assert(target.drop());
assert.commandWorked(source.insert([{_id: 1, a: 1}, {_id: 2, a: 2}]));
assert.commandWorked(target.insert([{_id: 1, b: 1}, {_id: 2, b: 2}, {_id: 3, b: 3}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({
actual: target.find().toArray(),
expected: [{_id: 1, a: 1, b: 1}, {_id: 2, a: 2, b: 2}, {_id: 3, b: 3}]
});
})();
// Test $merge when a field is presented in the source and the target and contains a
// sub-document value.
(function testMergeSubdocuments() {
// Source has a single element with a match in the target.
assert(source.drop());
assert(target.drop());
assert.commandWorked(source.insert({_id: 1, a: {b: 1}}));
assert.commandWorked(target.insert([{_id: 1, a: {c: 2}}, {_id: 3, b: 3}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq(
{actual: target.find().toArray(), expected: [{_id: 1, a: {b: 1}}, {_id: 3, b: 3}]});
// Source has multiple documents with matches in the target.
assert(source.drop());
assert(target.drop());
assert.commandWorked(source.insert([{_id: 1, a: {b: 1}}, {_id: 2, a: {b: 2}}]));
assert.commandWorked(target.insert([{_id: 1, a: 1, b: 1}, {_id: 2, a: 2}, {_id: 3, b: 3}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({
actual: target.find().toArray(),
expected: [{_id: 1, a: {b: 1}, b: 1}, {_id: 2, a: {b: 2}}, {_id: 3, b: 3}]
});
})();
// Test $merge when the source collection is empty. The target collection should not be
// modified.
(function testMergeWhenSourceIsEmpty() {
assert.commandWorked(source.deleteMany({}));
assert(target.drop());
assert.commandWorked(target.insert([{_id: 1, b: 1}, {_id: 2, b: 2}]));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({actual: target.find().toArray(), expected: [{_id: 1, b: 1}, {_id: 2, b: 2}]});
})();
// Test $merge does not insert a new document into the target collection if it was inserted
// into the source collection.
(function testMergeDoesNotInsertNewDocument() {
// Insert and merge a single document.
assert.commandWorked(source.insert({_id: 3, a: 3, b: "c"}));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({actual: target.find().toArray(), expected: [{_id: 1, b: 1}, {_id: 2, b: 2}]});
assert.commandWorked(source.deleteOne({_id: 3}));
// Insert and merge multiple documents.
assert.commandWorked(source.insert({_id: 3, a: 3, b: "c"}));
assert.commandWorked(source.insert({_id: 4, a: 4, c: "d"}));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({actual: target.find().toArray(), expected: [{_id: 1, b: 1}, {_id: 2, b: 2}]});
assert.commandWorked(source.deleteMany({_id: {$in: [3, 4]}}));
})();
// Test $merge doesn't modify the target collection if a document has been removed from the
// source collection.
(function testMergeDoesNotUpdateDeletedDocument() {
assert.commandWorked(source.deleteOne({_id: 1}));
assert.doesNotThrow(() => source.aggregate(pipeline));
assertArrayEq({actual: target.find().toArray(), expected: [{_id: 1, b: 1}, {_id: 2, b: 2}]});
})();
// Test $merge with an explicit 'on' field over a single or multiple document fields which
// differ from the _id field.
(function testMergeWithOnFields() {
if (FixtureHelpers.isSharded(source)) {
// Skip this test if the collection sharded, because an implicitly created sharded
// key of {_id: 1} will not be covered by a unique index created in this test, which
// is not allowed.
return;
}
// The 'on' fields contains a single document field.
dropWithoutImplicitRecreate(source.getName());
dropWithoutImplicitRecreate(target.getName());
assert.commandWorked(source.createIndex({a: 1}, {unique: true}));
assert.commandWorked(target.createIndex({a: 1}, {unique: true}));
assert.commandWorked(
source.insert([{_id: 1, a: 1, b: "a"}, {_id: 2, a: 2, b: "b"}, {_id: 3, a: 30, b: "c"}]));
assert.commandWorked(
target.insert([{_id: 1, a: 1, c: "x"}, {_id: 4, a: 30, c: "y"}, {_id: 5, a: 40, c: "z"}]));
assert.doesNotThrow(
() => source.aggregate(
[{$project: {_id: 0}}, {$merge: Object.assign({on: "a"}, mergeStage.$merge)}]));
assertArrayEq({
actual: target.find().toArray(),
expected: [
{_id: 1, a: 1, b: "a", c: "x"},
{_id: 4, a: 30, b: "c", c: "y"},
{_id: 5, a: 40, c: "z"}
]
});
// The 'on' fields contains multiple document fields.
dropWithoutImplicitRecreate(source.getName());
dropWithoutImplicitRecreate(target.getName());
assert.commandWorked(source.createIndex({a: 1, b: 1}, {unique: true}));
assert.commandWorked(target.createIndex({a: 1, b: 1}, {unique: true}));
assert.commandWorked(source.insert(
[{_id: 1, a: 1, b: "a", c: "x"}, {_id: 2, a: 2, b: "b"}, {_id: 3, a: 30, b: "c", c: "x"}]));
assert.commandWorked(
target.insert([{_id: 1, a: 1, b: "a"}, {_id: 4, a: 30, b: "c"}, {_id: 5, a: 40, c: "z"}]));
assert.doesNotThrow(
() => source.aggregate(
[{$project: {_id: 0}}, {$merge: Object.assign({on: ["a", "b"]}, mergeStage.$merge)}]));
assertArrayEq({
actual: target.find().toArray(),
expected: [
{_id: 1, a: 1, b: "a", c: "x"},
{_id: 4, a: 30, b: "c", c: "x"},
{_id: 5, a: 40, c: "z"}
]
});
assert.commandWorked(source.dropIndex({a: 1, b: 1}));
assert.commandWorked(target.dropIndex({a: 1, b: 1}));
})();
// Test $merge with a dotted path in the 'on' field.
(function testMergeWithDottedOnField() {
if (FixtureHelpers.isSharded(source)) {
// Skip this test if the collection sharded, because an implicitly created sharded
// key of {_id: 1} will not be covered by a unique index created in this test, which
// is not allowed.
return;
}
dropWithoutImplicitRecreate(source.getName());
dropWithoutImplicitRecreate(target.getName());
assert.commandWorked(source.createIndex({"a.b": 1}, {unique: true}));
assert.commandWorked(target.createIndex({"a.b": 1}, {unique: true}));
assert.commandWorked(source.insert([
{_id: 1, a: {b: "b"}, c: "x"},
{_id: 2, a: {b: "c"}, c: "y"},
{_id: 3, a: {b: 30}, b: "c"}
]));
assert.commandWorked(target.insert({_id: 2, a: {b: "c"}, d: "z"}));
assert.doesNotThrow(
() => source.aggregate(
[{$project: {_id: 0}}, {$merge: Object.assign({on: "a.b"}, mergeStage.$merge)}]));
assertArrayEq({
actual: target.find().toArray(),
expected: [
{_id: 2, a: {b: "c"}, c: "y", d: "z"},
]
});
})();
// Test $merge when the _id field is removed from the aggregate projection but is used in the
// $merge's 'on' field.
(function testMergeWhenDocIdIsRemovedFromProjection() {
// The _id is a single 'on' field (a default one).
dropWithoutImplicitRecreate(source.getName());
assert(target.drop());
assert.commandWorked(source.insert([{_id: 1, a: 1, b: "a"}, {_id: 2, a: 2, b: "b"}]));
assert.commandWorked(target.insert({_id: 1, b: "c"}));
assert.doesNotThrow(() => source.aggregate([{$project: {_id: 0}}, mergeStage]));
assertArrayEq({actual: target.find({}, {_id: 0}).toArray(), expected: [{b: "c"}]});
// The _id is part of the compound 'on' field.
dropWithoutImplicitRecreate(target.getName());
assert.commandWorked(target.insert({_id: 1, b: "c"}));
assert.commandWorked(source.createIndex({_id: 1, a: -1}, {unique: true}));
assert.commandWorked(target.createIndex({_id: 1, a: -1}, {unique: true}));
assert.doesNotThrow(() => source.aggregate([
{$project: {_id: 0}},
{$merge: Object.assign({on: ["_id", "a"]}, mergeStage.$merge)}
]));
assertArrayEq({actual: target.find({}, {_id: 0}).toArray(), expected: [{b: "c"}]});
assert.commandWorked(source.dropIndex({_id: 1, a: -1}));
assert.commandWorked(target.dropIndex({_id: 1, a: -1}));
})();
}());
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