title: why spark read csv generate three jobs
body: <p>I tried simple example on spark 2.1cloudra2:</p>
  
  <pre><code>val flightData2015 = spark
    .read
    .option("inferSchema", "true")
    .option("header", "true")
    .csv("/2015-summary.csv")
  </code></pre>
  
  <p>but when I check spark shell UI,I found it generate three jobs:
  <a href="https://i.stack.imgur.com/PrT8B.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PrT8B.jpg" alt="enter image description here"></a></p>
  
  <p>I think every action should related to a job,am I right? I do some experiment found out every option can generate a job. Does option act like action? please help understand this situation.</p>