LogReader

LogReader 提供了一个 SmartEDB 事务日志记录事务日志读取器。类定义

类定义

    public class LogReader
    {
        /**
        *  Transaction log reader constructor.
        *  @param con Connection to the pipe database or to the database where log is replayed
        *  @param filePath Path to the transaction log file
        */
        public LogReader(Connection con, String filePath)
        {
            this.con = con;
            this.filePath = filePath;
        }
 
        /**
        *  Apply transactions from the log to the database up to the specified label id
        *  @param labelId Label ID
        */
        public void apply(int labelId)
        {
            applyLog(con.id, filePath, labelId);
        }
 
        /**
        *  Apply transactions from the log to the database up to the end of log
        */
        public void apply()
        {
            applyLog(con.id, filePath, -1);
        }
 
        /**
        *  Information gathered from log file
        */
        public static class LogInfo
        {
            /**
            *  Transaction counter at start of log
            */
            public long    startTransCounter;
 
            /**
            *  Transaction counter at end of log
            */
            public long    stopTransCounter;
 
            /**
            *  Count of stored transactions
            */
            public long    storedTransactions;
 
            /**
            *  Size of single disk page
            */
            public int     diskPageSize;
 
            /**
            *  Size of in-memory database page
            */
            public int     pageSize;
             
            /**
            *  Size of log in bytes
            */
            public long    logSize;
 
            /**
            *  List of labels it the log
            */
            public String[] labels;
             
            /**
            *  If log covered with CRC32
            */
            public boolean crc;
 
            /**
            *  If log written with alignment
            */
            public boolean aligned;
             
            /**
            *  If log compatible with current dict.
            */
            public boolean dictionaryCompat;
 
            /**
            *  If log suitable to be applied
            */
            public boolean transactionApplyCompat;
 
            /**
            *  If log suitable to be appended
            */
            public boolean transactionAppendCompat;
 
            /**
            *  If log finished correctly
            */
            public boolean notCorrupted;
 
            /**
            *  Log is applicable for synchronisation with external database (saved with flag MCO_TRANSLOG_ITERABLE)
            */
            public boolean iteratable;
        }
     
        /**
        *  Get information about the log file
        */
        public LogInfo getInfo()
        {
            return getLogReaderInfo(con.id, filePath);
        }
 
        /**
        *  Interface for iterator through transaction log objects
        */
        public interface LogIterator
        {
            /**
            *  Callback on object creation
            *  @param obj Created object
            */
            void create(Object obj);
 
            /**
            *  Callback on object update
            *  @param obj Updated object
            */
            void update(Object obj);
 
            /**
            *  Callback on object delete
            *  @param obj Deleted object
            */
            void delete(Object obj);
 
            /**
            *  Callback on delete all class instances
            *  @param type Type of the deleted objects
            */
            void deleteAll(Class type);
 
            /**
            *  Callback on end of transaction. Is called if option RT_OPTION_MARK_LAST_OBJ set
            */
            void endOfTransaction();
        }
 
        /**
        *  Iterate through transaction log file entries
        *  @param iterator Iterator class which method will be invoked for all log entries
        *  @param memSize Size of temporary database used to fetch objects 
        * (should be large enough to fit the largest objects)
        */
        public void iterateFile(LogIterator iterator, long memSize, long hint)
        {
            Database db = con.db;
            iterateLog(0, filePath, db.structsList.toArray(), db.classes, db.hasInmemDistribClasses, 
                    db.hasDiskDistribClasses, db.totalFields, db.totalIndices, db.totalKeys, 
                    db.events.size(), db.config, iterator, memSize, hint, null);
        }
 
        /**
        *  Iterate through transaction log entries fetched from pipe
        *  @param iterator Iterator class which method will be invoked for all log entries
        *  @param memSize Size of temporary database used to fetch objects (should be large enough to fit the largest objects)
        */
        public void iteratePipe(LogIterator iterator, long memSize, long hint)
        {
            Database db = con.db;
            iterateLog(con.id, filePath, db.structsList.toArray(), db.classes, db.hasInmemDistribClasses, 
                    db.hasDiskDistribClasses, db.totalFields, db.totalIndices, db.totalKeys, 
                    db.events.size(), db.config, iterator, memSize, hint, null);
        }
        public void iteratePipe(LogIterator iterator, long memSize, long hint, Database.Device pipe)
        {
            Database db = con.db;
            iterateLog(con.id, filePath, db.structsList.toArray(), db.classes, db.hasInmemDistribClasses, 
                    db.hasDiskDistribClasses, db.totalFields, db.totalIndices, db.totalKeys, 
                    db.events.size(), db.config, iterator, memSize, hint, pipe);
        }
 
        /**
        *  Stop method iteratePipe specified by connection of current LogReader
        */
        public void stopPipeIteration()
        {
            stopIteration(con.id);
        }
 
        Connection con;
        String filePath;
 
        /**
        *  Internal method, should not be called by application
        */
        public int invokeCallback(LogIterator iterator, int operation, int classId, long handle)
        {
            ...
        }
 
        private native void applyLog(long con, String filePath, int labelId);
        private native LogReader.LogInfo getLogReaderInfo(long con, String filePath);
        private native void iterateLog(long con, String filePath, Object[] structs,
                            Database.ClassDescriptor[] classes, 
                            boolean hasInmemDistribClasses, 
                            boolean hasDiskDistribClasses,
                            int totalFields, int totalIndices, int totalKeys, 
                            int totalEvents, int config,
                            LogIterator iterator, long memSize, long hint, 
                            Database.Device pipe);
        private native void stopIteration(long con);
    }