protected LogEntry toLogEntry(DatabaseEntry logEntry) {
        if (logEntry == null || logEntry.getSize() == 0) {
            return null;
        }
        return this.logEntryDecoder.decode(logEntry.getData());
    }
First log index and last log index key in configuration column family.
jraft-extension/bdb-log-storage-impl/src/main/java/com/alipay/sofa/jraft/storage/impl/BDBLogStorage.java