Comment 27 for bug 1589014

Reviewed: https://review.opencontrail.org/21490
Committed: http://github.org/Juniper/contrail-controller/commit/10c96256a83c61ff15790afb6cbda8dc326a9a56
Submitter: Zuul
Branch: master

commit 10c96256a83c61ff15790afb6cbda8dc326a9a56
Author: Édouard Thuleau <email address hidden>
Date: Tue Jun 28 16:21:47 2016 +0200

[VNC API server] Improve cassandra object_read method

Use pycassa 'multiget' method when it's possible.
Two cases can be distinguished:
- cannot determine return size when fetching multi keys with start and
finish column conditions. In that case try to fetch data with
multiget and if it raises 'OverflowError' try to fetch data with
'xget' method.
- when the column length is defined, we calculate if we can fetch all
data in one 'multiget' call, if not use all necessary 'get' calls

Change-Id: I2497ea365e25e7cfa6abd8c35b36929f7b5e7806
Partial-Bug: #1589014