When READ_LATEST is specified the server will always return committed writes at
the time the request was received. This type of read does not return a snapshot
timestamp and is not repeatable.
In ACID terms this corresponds to Isolation mode: "Read Committed"
This is the default mode.
When READ_AT_SNAPSHOT is specified the server will attempt to perform a read
at the provided timestamp. If no timestamp is provided the server will take the
current time as the snapshot timestamp. In this mode reads are repeatable, i.e.
all future reads at the same timestamp will yield the same data. This is
performed at the expense of waiting for in-flight transactions whose timestamp
is lower than the snapshot's timestamp to complete, so it might incur a latency
In ACID terms this, by itself, corresponds to Isolation mode "Repeatable
Read". If all writes to the scanned tablet are made externally consistent,
then this corresponds to Isolation mode "Strict-Serializable".
Note: there currently "holes", which happen in rare edge conditions, by which writes
are sometimes not externally consistent even when action was taken to make them so.
In these cases Isolation may degenerate to mode "Read Committed". See KUDU-430.
Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
name - the name of the enum constant to be returned.