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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 } );
indexCursorName = 'BtreeCursor ' + indexKeyField + '_1';
}
setIndex( 'a' );
/** Validate the prefix of 'str'. */
function assertPrefix( prefix, str ) {
assert.eq( prefix, str.substring( 0, prefix.length ) );
}
/** @return count when hinting the index to use. */
function hintedCount( query ) {
assertPrefix( indexCursorName, t.find( query ).hint( indexKeySpec ).explain().cursor );
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 ) );
assert.eq( 'BasicCursor', t.find( query ).explain().cursor );
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 ) );
assert.eq( 'BasicCursor', t.find( query ).explain().cursor );
// 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 ) );
assertPrefix( indexCursorName, t.find( query ).explain().cursor );
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 ) );
assert.eq( 'BasicCursor', t.find( query ).explain().cursor );
// 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( 'BasicCursor', t.find( query ).explain().cursor );
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 );
// Top level $exists:true queries match the proper number of documents and allow the sparse index.
assertExists( { a:{ $exists:true } } );
assertExists( { 'a.x':{ $exists:true } }, 1 );
assertExists( { b:{ $exists:true } }, 1 );
assertExists( { a:{ $not:{ $exists:false } } } );
// 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 );
// 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.
assertExistsUnindexed( { $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 is disallowed even for $exists:true.
assertExistsUnindexed( { 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() );
assert.eq( 'BtreeCursor a_1', t.find( { a:{ $exists:false } } ).explain().cursor );
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