Accumulo supports the ability to present an isolated view of rows when scanning. There are three possible ways that a row could change in accumulo :
IsolatedScanner
to obtain an
isolated view of an accumulo table. When using the regular scanner it is
possible to see a non isolated view of a row. For example if a mutation
modifies three columns, it is possible that you will only see two of those
modifications. With the isolated scanner either all three of the changes are
seen or none. For an example of this try running the
InterferenceTest
example.
At this time there is no client side isolation support for the
BatchScanner
. You may consider using the
WholeRowIterator
with the BatchScanner
to achieve
isolation though. This drawback of doing this is that entire rows are read into
memory on the server side. If a row is too big, it may crash a tablet server.
The IsolatedScanner
buffers rows on the client side so a large row will not crash a tablet server.
See the user manual's chapter on iterator design for more information on considerations when Isolation is enabled.