// We filter out operations that didn't produce a write error to avoid causing a
// duplicate key error when retrying the operations.
for (let writeError of res.writeErrors) {
    assert.lt(writeError.index,
              opsExecuted.length,
              "A write error was returned for an operation outside the list" +
                  " of operations executed: " + tojson(res));
    opsToRetry.push(opsExecuted[writeError.index]);
}