This is the default (for single-statement requests). No timestamp vector is used
in the index scan.
This is also the fastest mode, because we avoid the cost of obtaining the vector,
and we also avoid any wait for the index to catch up to the vector.
This implements strong consistency per request.
Before processing the request, a current vector is obtained.
The vector is used as a lower bound for the statements in the request.
If there are DML statements in the request, RYOW is also applied within the request.
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.