Fixed overflow on large range with high number of partitions

[JeroenWarmerdam]

The following use case causes an overflow when creating the partitions inside JdbcRDD:

val jdbcRDD = new JdbcRDD(sc, () =>
      DriverManager.getConnection(url, username, password),
      "SELECT id FROM documents WHERE ? <= id AND id <= ?",
      lowerBound = 1131544775L,
      upperBound = 567279358897692673L,
      numPartitions = 20,
      mapRow = r => (r.getLong("id"))
)

This is fixed by swapping division and multiplication in the creation of partitions.

[AmplabJenkins]

Can one of the admins verify this patch?

[srowen]

No, this changes the result! For example, (3 * 4) / 5 == 2 but 3 * (4 / 5) == 0. It's a good point though, but why not just cast i to long? (You will need to open a JIRA for a minor bug.)

[andrewor14]

Hi @JeroenWarmerdam could you open an associated JIRA and add it to the title? See how other PRs are opened.

[srowen]

This appears to be superseded by #4701 Do you mind closing this PR?