Creates a new read session. A read session divides the contents of a
BigQuery table into one or more streams, which can then be used to read
data from the table. The read session also specifies properties of the
data to be read, such as a list of columns or a push-down filter describing
the rows to be returned.
A particular row can be read by at most one stream. When the caller has
reached the end of each stream in the session, then all the data in the
table has been read.
Data is assigned to each stream such that roughly the same number of
rows can be read from each stream. Because the server-side unit for
assigning data is collections of rows, the API does not guarantee that
each stream will return the same number or rows. Additionally, the
limits are enforced based on the number of pre-filtered rows, so some
filters can lead to lopsided assignments.
Read sessions automatically expire 6 hours after they are created and do
not require manual clean-up by the caller.
Splits a given ReadStream into two ReadStream objects. These
ReadStream objects are referred to as the primary and the residual
streams of the split. The original ReadStream can still be read from in
the same manner as before. Both of the returned ReadStream objects can
also be read from, and the rows returned by both child streams will be
the same as the rows read from the original stream.
Moreover, the two child streams will be allocated back-to-back in the
original ReadStream. Concretely, it is guaranteed that for streams
original, primary, and residual, that original[0-j] = primary[0-j] and
original[j-n] = residual[0-m] once the streams have been read to
completion.