// SERVER-2831 Demonstration of sparse index matching semantics in a multi index $or query. t = db.jstests_orh; t.drop(); t.ensureIndex( {a:1}, {sparse:true} ); t.ensureIndex( {b:1,a:1} ); t.remove(); t.save( {b:2} ); assert.eq( 0, t.count( {a:null} ) ); assert.eq( 1, t.count( {b:2,a:null} ) ); assert.eq( 1, t.count( {$or:[{b:2,a:null},{a:null}]} ) ); // Is this desired? assert.eq( 0, t.count( {$or:[{a:null},{b:2,a:null}]} ) );