Make the default number of partions in json-file something larger than 1

[ingomueller-net]

If you say:

json-file("...")

the computation will run with only a single partition, doing the scan inside a single executor. A much better default value would be the number of executors, or 10 times that, or simply 100, IMO.

[ghislainfourny]

Agreed. 100 would be a better default number.

[ghislainfourny]

The workaround is:

json-file("...", 100)