copy to from files, urls and what not

[piccolbo]

using https://spark.apache.org/docs/latest/sql-programming-guide.html#loading-data-programmatically
or LOAD INPATH, see db insert into

[piccolbo]

CREATE TEMPORARY TABLE impressions
USING org.apache.spark.sql.jdbc
OPTIONS (
url "jdbc:postgresql:dbserver",
dbtable "impressions"
)

Oops this doesn't work in hivql, it's load inpath or bust

[piccolbo]

After some research dplyr doesn't have a feature to load data in a db that is not in memory. Propose
the following interface:

• extension of copy_to
• when argument is a character vector, it is construed as a collection of URL
• problem is inferring schema. One possibility is read a few rows with read table, use copy to to create table, then overwrite.