gistfile1.txt

db.adminCommand({ setParameter: 1, internalQueryExecYieldIterations: 100000 });
db.adminCommand({ setParameter: 1, internalQueryExecYieldPeriodMS: 10000 });

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

for ( i=0; i< 100000; i++ ){
    t.save( { x : i } );
}

s = startParallelShell(
  "for (i=0; i < 50000; i++) { db.background_index_build.remove({x: i*12347 % 50000}); }"
);

t.createIndex( { x: 1 }, { background: true } );
s();
var a = t.find().sort({x:1});
assert.eq(a.length(), 50000);