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// Tests for $exists against documents that store a null value
//
// A document with a missing value for an indexed field
// is indexed *as if* it had the value 'null' explicitly.
// Therefore:
// { b : 1 }
// { a : null, b : 1 }
// look identical based on a standard index on { a : 1 }.
//
// -- HOWEVER!! --
// A sparse index on { a : 1 } would include { a : null, b : 1 },
// but would not include { b : 1 }. In this case, the two documents
// are treated equally.
//
// Also, super special edge case around sparse, compound indexes
// from Mathias:
// If we have a sparse index on { a : 1, b : 1 }
// And we insert docs {}, { a : 1 },
// { b : 1 }, and { a : 1, b : 1 }
// everything but {} will have an index entry.
// Let's make sure we handle this properly!
t = db.jstests_existsb;
t.drop();
t.save({});
t.save({a: 1});
t.save({b: 1});
t.save({a: 1, b: null});
t.save({a: 1, b: 1});
/** run a series of checks, just on the number of docs found */
function checkExistsNull() {
// Basic cases
assert.eq(3, t.count({a: {$exists: true}}));
assert.eq(2, t.count({a: {$exists: false}}));
assert.eq(3, t.count({b: {$exists: true}}));
assert.eq(2, t.count({b: {$exists: false}}));
// With negations
assert.eq(3, t.count({a: {$not: {$exists: false}}}));
assert.eq(2, t.count({a: {$not: {$exists: true}}}));
assert.eq(3, t.count({b: {$not: {$exists: false}}}));
assert.eq(2, t.count({b: {$not: {$exists: true}}}));
// Both fields
assert.eq(2, t.count({a: 1, b: {$exists: true}}));
assert.eq(1, t.count({a: 1, b: {$exists: false}}));
assert.eq(1, t.count({a: {$exists: true}, b: 1}));
assert.eq(1, t.count({a: {$exists: false}, b: 1}));
// Both fields, both $exists
assert.eq(2, t.count({a: {$exists: true}, b: {$exists: true}}));
assert.eq(1, t.count({a: {$exists: true}, b: {$exists: false}}));
assert.eq(1, t.count({a: {$exists: false}, b: {$exists: true}}));
assert.eq(1, t.count({a: {$exists: false}, b: {$exists: false}}));
}
// with no index, make sure we get correct results
checkExistsNull();
// try with a standard index
t.createIndex({a: 1});
checkExistsNull();
// try with a sparse index
t.dropIndexes();
t.createIndex({a: 1}, {sparse: true});
checkExistsNull();
// try with a compound index
t.dropIndexes();
t.createIndex({a: 1, b: 1});
checkExistsNull();
// try with sparse compound index
t.dropIndexes();
t.createIndex({a: 1, b: 1}, {sparse: true});
checkExistsNull();
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