(db [system] [system ^Date valid-time] [system ^Date valid-time ^Date transaction-time] "Will return the latest value of the db currently known. Non-blocking. When a valid time is specified then returned db value contains only those documents whose valid time is not after the specified. Non-blocking. When both valid and transaction time are specified returns a db value as of the valid and transaction time. Will block until the transaction time is present in the index.")