Automatically set .batchSize based on the primary key

[msmygit]

Automatically set .batchSize to 1 if a table has a primary key that is also the partition key. Example tables as follows:

Example 1:

CREATE TABLE IF NOT EXISTS ks1.tbl1 (
  pk1 int,
  pk2 long,
  c1 text,
  c2 uuid,
  PRIMARY KEY ((pk1,pk2))
);

Example 2:

CREATE TABLE IF NOT EXISTS ks1.tbl1 (
  c1 text PRIMARY KEY,
  c2 uuid
);

or use the default.

[mieslep]

@msmygit can I suggest we go one further...we know the partition key, and we're selecting by token range so should get the origin records in partition key order. Maybe we make this be a "max batch size" and allow it to be a really big number, and then automatically send the batch when the partition key changes?

Which is to say, the batch will be the smaller of "records in the partition" or .batchSize configuration setting? In this way, we would avoid multi-partition batches.