collection_migrate: Migrate documents to another collection
In solrium: General Purpose R Interface to 'Solr'

Migrate documents to another collection

collection_migrate(
  conn,
  name,
  target.collection,
  split.key,
  forward.timeout = NULL,
  async = NULL,
  raw = FALSE,
  callopts = list()
)

`conn`	A solrium connection object, see SolrClient
`name`	(character) The name of the core to be created. Required
`target.collection`	(character) Required. The name of the target collection to which documents will be migrated
`split.key`	(character) Required. The routing key prefix. For example, if uniqueKey is a!123, then you would use split.key=a!
`forward.timeout`	(integer) The timeout (seconds), until which write requests made to the source collection for the given `split.key` will be forwarded to the target shard. Default: 60
`async`	(character) Request ID to track this action which will be processed asynchronously
`raw`	(logical) If `TRUE`, returns raw data
`callopts`	curl options passed on to crul::HttpClient

## Not run: 
(conn <- SolrClient$new())

# create collection
if (!conn$collection_exists("migrate_from")) {
  conn$collection_create(name = "migrate_from")
  # OR: bin/solr create -c migrate_from
}

# create another collection
if (!conn$collection_exists("migrate_to")) {
  conn$collection_create(name = "migrate_to")
  # OR bin/solr create -c migrate_to
}

# add some documents
file <- system.file("examples", "books.csv", package = "solrium")
x <- read.csv(file, stringsAsFactors = FALSE)
conn$add(x, "migrate_from")

# migrate some documents from one collection to the other
## FIXME - not sure if this is actually working....
# conn$collection_migrate("migrate_from", "migrate_to", split.key = "05535")

## End(Not run)