mongodb/jstests/ore.js

// verify that index direction is considered when deduping based on an earlier
// index

t = db.jstests_ore;
t.drop();

t.ensureIndex( {a:-1} )
t.ensureIndex( {b:1} );

t.save( {a:1,b:1} );
t.save( {a:2,b:1} );

assert.eq( 2, t.count( {$or:[{a:{$in:[1,2]}},{b:1}]} ) );