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/**
* Test that queries containing $elemMatch correctly use an index if each child expression is
* compatible with the index.
*/
(function() {
"use strict";
load("jstests/libs/analyze_plan.js");
const coll = db.elemMatch_index;
coll.drop();
assert.writeOK(coll.insert({a: 1}));
assert.writeOK(coll.insert({a: [{}]}));
assert.writeOK(coll.insert({a: [1, null]}));
assert.writeOK(coll.insert({a: [{type: "Point", coordinates: [0, 0]}]}));
assert.commandWorked(coll.createIndex({a: 1}, {sparse: true}));
function assertIndexResults(coll, query, useIndex, nReturned) {
const explainPlan = coll.find(query).explain("executionStats");
assert.eq(isIxscan(explainPlan.queryPlanner.winningPlan), useIndex);
assert.eq(explainPlan.executionStats.nReturned, nReturned);
}
assertIndexResults(coll, {a: {$elemMatch: {$exists: false}}}, false, 0);
// An $elemMatch predicate is treated as nested, and the index should be used for $exists:true.
assertIndexResults(coll, {a: {$elemMatch: {$exists: true}}}, true, 3);
// $not within $elemMatch should not attempt to use a sparse index for $exists:false.
assertIndexResults(coll, {a: {$elemMatch: {$not: {$exists: false}}}}, false, 3);
assertIndexResults(coll, {a: {$elemMatch: {$gt: 0, $not: {$exists: false}}}}, false, 1);
// $geo within $elemMatch should not attempt to use a non-geo index.
assertIndexResults(
coll,
{
a: {
$elemMatch: {
$geoWithin: {
$geometry:
{type: "Polygon", coordinates: [[[0, 0], [0, 1], [1, 0], [0, 0]]]}
}
}
}
},
false,
1);
// $in with a null value within $elemMatch should use a sparse index.
assertIndexResults(coll, {a: {$elemMatch: {$in: [null]}}}, true, 1);
// $eq with a null value within $elemMatch should use a sparse index.
assertIndexResults(coll, {a: {$elemMatch: {$eq: null}}}, true, 1);
// A negated regex within $elemMatch should not use an index, sparse or not.
assertIndexResults(coll, {a: {$elemMatch: {$not: {$in: [/^a/]}}}}, false, 3);
coll.dropIndexes();
assert.commandWorked(coll.createIndex({a: 1}));
assertIndexResults(coll, {a: {$elemMatch: {$not: {$in: [/^a/]}}}}, false, 3);
})();
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