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/**
* Tests that the server behaves as expected when an $merge stage is targeting a collection which is
* involved in the aggregate in some other way, e.g. as the source namespace or via a $lookup. We
* disallow this combination in an effort to prevent the "halloween problem" of a never-ending
* query.
*
* This test issues queries over views, so cannot be run in passthroughs which implicitly shard
* collections.
* @tags: [assumes_unsharded_collection]
*/
(function() {
'use strict';
load('jstests/aggregation/extras/merge_helpers.js'); // For 'withEachMergeMode'.
load('jstests/libs/fixture_helpers.js'); // For 'FixtureHelpers'.
const testDB = db.getSiblingDB("merge_to_referenced_coll");
const coll = testDB.test;
withEachMergeMode(({whenMatchedMode, whenNotMatchedMode}) => {
coll.drop();
// Seed the collection to ensure each pipeline will actually do something.
assert.commandWorked(coll.insert({_id: 0}));
// Each of the following assertions will somehow use $merge to write to a namespace that is
// being read from elsewhere in the pipeline.
const assertFailsWithCode = ((fn) => {
const error = assert.throws(fn);
assert.contains(error.code, [51188, 51079]);
});
// Test $merge to the aggregate command's source collection.
assertFailsWithCode(() => coll.aggregate([{
$merge:
{into: coll.getName(), whenMatched: whenMatchedMode, whenNotMatched: whenNotMatchedMode}
}]));
// Test $merge to the same namespace as a $lookup which is the same as the aggregate
// command's source collection.
assertFailsWithCode(() => coll.aggregate([
{$lookup: {from: coll.getName(), as: "x", localField: "f_id", foreignField: "_id"}},
{
$merge: {
into: coll.getName(),
whenMatched: whenMatchedMode,
whenNotMatched: whenNotMatchedMode
}
}
]));
// Test $merge to the same namespace as a $lookup which is *not* the same as the aggregate
// command's source collection.
assertFailsWithCode(() => coll.aggregate([
{$lookup: {from: "bar", as: "x", localField: "f_id", foreignField: "_id"}},
{$merge: {into: "bar", whenMatched: whenMatchedMode, whenNotMatched: whenNotMatchedMode}}
]));
// Test $merge to the same namespace as a $graphLookup.
assertFailsWithCode(() => coll.aggregate([
{
$graphLookup: {
from: "bar",
startWith: "$_id",
connectFromField: "_id",
connectToField: "parent_id",
as: "graph",
}
},
{
$merge: {
into: "bar",
whenMatched: whenMatchedMode,
whenNotMatched: whenNotMatchedMode
}
}
]));
// Test $merge to the same namespace as a $lookup which is nested within another $lookup.
assertFailsWithCode(() => coll.aggregate([
{
$lookup: {
from: "bar",
as: "x",
let : {},
pipeline: [{$lookup: {from: "TARGET", as: "y", pipeline: []}}]
}
},
{
$merge: {
into: "TARGET",
whenMatched: whenMatchedMode,
whenNotMatched: whenNotMatchedMode
}
}
]));
// Test $merge to the same namespace as a $lookup which is nested within a $facet.
assertFailsWithCode(() => coll.aggregate([
{
$facet: {
y: [{$lookup: {from: "TARGET", as: "y", pipeline: []}}],
}
},
{$merge: {into: "TARGET", whenMatched: whenMatchedMode, whenNotMatched: whenNotMatchedMode}}
]));
assertFailsWithCode(() => coll.aggregate([
{
$facet: {
x: [{$lookup: {from: "other", as: "y", pipeline: []}}],
y: [{$lookup: {from: "TARGET", as: "y", pipeline: []}}],
}
},
{$merge: {into: "TARGET", whenMatched: whenMatchedMode, whenNotMatched: whenNotMatchedMode}}
]));
// Test that we use the resolved namespace of a view to detect this sort of halloween
// problem.
assert.commandWorked(
testDB.runCommand({create: "view_on_TARGET", viewOn: "TARGET", pipeline: []}));
assertFailsWithCode(() => testDB.view_on_TARGET.aggregate([
{$merge: {into: "TARGET", whenMatched: whenMatchedMode, whenNotMatched: whenNotMatchedMode}}
]));
assertFailsWithCode(() => coll.aggregate([
{
$facet: {
x: [{$lookup: {from: "other", as: "y", pipeline: []}}],
y: [{
$lookup: {
from: "yet_another",
as: "y",
pipeline: [{$lookup: {from: "view_on_TARGET", as: "z", pipeline: []}}]
}
}],
}
},
{
$merge: {
into: "TARGET",
whenMatched: whenMatchedMode,
whenNotMatched: whenNotMatchedMode
}
}
]));
function generateNestedPipeline(foreignCollName, numLevels) {
let pipeline = [{"$lookup": {pipeline: [], from: foreignCollName, as: "same"}}];
for (let level = 1; level < numLevels; level++) {
pipeline = [{"$lookup": {pipeline: pipeline, from: foreignCollName, as: "same"}}];
}
return pipeline;
}
const nestedPipeline = generateNestedPipeline("lookup", 20).concat([
{$merge: {into: "lookup", whenMatched: whenMatchedMode, whenNotMatched: whenNotMatchedMode}}
]);
assertFailsWithCode(() => coll.aggregate(nestedPipeline));
testDB.dropDatabase();
});
}());
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