[Spark] RDD take() method: overestimate too much

In the comment (Line 1083), it says: "Otherwise, interpolate the number of partitions we need to try, but overestimate it by 50%."

`(1.5 * num * partsScanned / buf.size).toInt` is the guess of "num of total partitions needed". In every iteration, we should consider the increment `(1.5 * num * partsScanned / buf.size).toInt - partsScanned`
Existing implementation 'exponentially' grows `partsScanned ` ( roughly: `x_{n+1} >= (1.5 + 1) x_n`)

This could be a performance problem. (unless this is the intended behavior)


Infix Methods
Don't use infix notation for methods that aren't operators. For example, instead of list map func, use list.map(func), or instead of string contains "foo", use string.contains("foo"). This is to improve familiarity to developers coming from other languages.

https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide