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// Sparse indexes are disallowed for $exists:false queries. SERVER-3918
t = db.jstests_existsa;
t.drop();
t.save({});
t.save({a: 1});
t.save({a: {x: 1}, b: 1});
/** Configure testing of an index { <indexKeyField>:1 }. */
function setIndex(_indexKeyField) {
indexKeyField = _indexKeyField;
indexKeySpec = {};
indexKeySpec[indexKeyField] = 1;
t.ensureIndex(indexKeySpec, {sparse: true});
}
setIndex('a');
/** @return count when hinting the index to use. */
function hintedCount(query) {
return t.find(query).hint(indexKeySpec).itcount();
}
/** The query field does not exist and the sparse index is not used without a hint. */
function assertMissing(query, expectedMissing, expectedIndexedMissing) {
expectedMissing = expectedMissing || 1;
expectedIndexedMissing = expectedIndexedMissing || 0;
assert.eq(expectedMissing, t.count(query));
// We also shouldn't get a different count depending on whether
// an index is used or not.
assert.eq(expectedIndexedMissing, hintedCount(query));
}
/** The query field exists and the sparse index is used without a hint. */
function assertExists(query, expectedExists) {
expectedExists = expectedExists || 2;
assert.eq(expectedExists, t.count(query));
// An $exists:true predicate generates no index filters. Add another predicate on the index key
// to trigger use of the index.
andClause = {};
andClause[indexKeyField] = {
$ne: null
};
Object.extend(query, {$and: [andClause]});
assert.eq(expectedExists, t.count(query));
assert.eq(expectedExists, hintedCount(query));
}
/** The query field exists and the sparse index is not used without a hint. */
function assertExistsUnindexed(query, expectedExists) {
expectedExists = expectedExists || 2;
assert.eq(expectedExists, t.count(query));
// Even with another predicate on the index key, the sparse index is disallowed.
andClause = {};
andClause[indexKeyField] = {
$ne: null
};
Object.extend(query, {$and: [andClause]});
assert.eq(expectedExists, t.count(query));
assert.eq(expectedExists, hintedCount(query));
}
// $exists:false queries match the proper number of documents and disallow the sparse index.
assertMissing({a: {$exists: false}});
assertMissing({a: {$not: {$exists: true}}});
assertMissing({$and: [{a: {$exists: false}}]});
assertMissing({$or: [{a: {$exists: false}}]});
assertMissing({$nor: [{a: {$exists: true}}]});
assertMissing({'a.x': {$exists: false}}, 2, 1);
// Currently a sparse index is disallowed even if the $exists:false query is on a different field.
assertMissing({b: {$exists: false}}, 2, 1);
assertMissing({b: {$exists: false}, a: {$ne: 6}}, 2, 1);
assertMissing({b: {$not: {$exists: true}}}, 2, 1);
// Top level $exists:true queries match the proper number of documents
// and use the sparse index on { a : 1 }.
assertExists({a: {$exists: true}});
// Nested $exists queries match the proper number of documents and disallow the sparse index.
assertExistsUnindexed({$nor: [{a: {$exists: false}}]});
assertExistsUnindexed({$nor: [{'a.x': {$exists: false}}]}, 1);
assertExistsUnindexed({a: {$not: {$exists: false}}});
// Nested $exists queries disallow the sparse index in some cases where it is not strictly
// necessary to do so. (Descriptive tests.)
assertExistsUnindexed({$nor: [{b: {$exists: false}}]}, 1); // Unindexed field.
assertExists({$or: [{a: {$exists: true}}]}); // $exists:true not $exists:false.
// Behavior is similar with $elemMatch.
t.drop();
t.save({a: [{}]});
t.save({a: [{b: 1}]});
t.save({a: [{b: 1}]});
setIndex('a.b');
assertMissing({a: {$elemMatch: {b: {$exists: false}}}});
// A $elemMatch predicate is treated as nested, and the index should be used for $exists:true.
assertExists({a: {$elemMatch: {b: {$exists: true}}}});
// A non sparse index will not be disallowed.
t.drop();
t.save({});
t.ensureIndex({a: 1});
assert.eq(1, t.find({a: {$exists: false}}).itcount());
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