If "snapshot" is non-NULL, read as of the supplied snapshot
(which must belong to the DB that is being read and which must
not have been released). If "snapshot" is null, use an impliicit
snapshot of the state at the beginning of this read operation.
Default: null
If "snapshot" is non-NULL, read as of the supplied snapshot (which must belong to the DB that is being read and which must not have been released). If "snapshot" is null, use an impliicit snapshot of the state at the beginning of this read operation. Default: null