Package org.apache.derby.impl.store.raw.log

Class LogCounter

  • All Implemented Interfaces:
    java.io.Externalizable, java.io.Serializable, Formatable, TypedFormat, DatabaseInstant, LogInstant
    public class LogCounter
extends java.lang.Object
implements LogInstant
    A very simple log instant implementation. Within the stored log record a log counter is represented as a long, hence the getValueAsLong() method. Outside the LogFactory the instant is passed around as a LogCounter (through its LogInstant interface). The way the long is encoded is such that < == > correctly tells if one log instant is lessThan, equals or greater than another.
    See Also:
    Serialized Form

    • Field Detail

      • INVALID_LOG_INSTANT

        public static final long INVALID_LOG_INSTANT
        A well defined value of an invalid log instant.
        See Also:
        Constant Field Values

      • DERBY_10_0_MAX_LOGFILE_NUMBER

        public static final long DERBY_10_0_MAX_LOGFILE_NUMBER
        See Also:
        Constant Field Values

      • fileNumber

        private long fileNumber

      • filePosition

        private long filePosition

    • Constructor Detail

      • LogCounter

        public LogCounter​(long value)

      • LogCounter

        public LogCounter​(long fileNumber,
                  long position)

      • LogCounter

        public LogCounter()
        Public niladic constructor needed for Formatable interface.

    • Method Detail

      • makeLogInstantAsLong

        public static final long makeLogInstantAsLong​(long filenum,
                                              long filepos)
        Static functions that can only be used inside the RawStore's log factory which passes the log counter around encoded as a long

      • getLogFilePosition

        public static final long getLogFilePosition​(long valueAsLong)

      • getLogFileNumber

        public static final long getLogFileNumber​(long valueAsLong)

      • lessThan

        public boolean lessThan​(DatabaseInstant other)
        LogScan methods
        Specified by:
        lessThan in interface DatabaseInstant
        Parameters:
        other - a DatabaseInstant from the same database as this.
        Returns:
        the comparison result. If 'other' is from another database the result is undefined.

      • equals

        public boolean equals​(java.lang.Object other)
        Description copied from interface: DatabaseInstant
        Return true if this DatabaseInstant equals DatabaseInstant from the same database.
        Specified by:
        equals in interface DatabaseInstant
        Overrides:
        equals in class java.lang.Object
        Parameters:
        other - a DatabaseInstant from the same database as this.
        Returns:
        the comparison result. If 'other' is from another database the result is undefined.

      • next

        public DatabaseInstant next()
        Description copied from interface: DatabaseInstant
        Return the next higher DatabaseInstant. There is no requirement that a transaction with the next instant exist in the database. It is required that this.lessThan( this.next()), and that no instant can be between this and this.next(). If the DatabaseInstant is implemented using a integer then next() should return a new DatabaseInstant formed by adding one to the integer.
        Specified by:
        next in interface DatabaseInstant
        Returns:
        the next possible DatabaseInstant

      • prior

        public DatabaseInstant prior()
        Description copied from interface: DatabaseInstant
        Return the next lower DatabaseInstant. There is no requirement that a transaction with the next instant exist in the database. It is required that this.prior().lessThan( this), and that no instant can be between this and this.prior(). If the DatabaseInstant is implemented using a integer then prior() should return a new DatabaseInstant formed by subtracting one from the integer.
        Specified by:
        prior in interface DatabaseInstant
        Returns:
        the prior possible DatabaseInstant

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.Object

      • toString

        public java.lang.String toString()
        Description copied from interface: DatabaseInstant
        Convert the database instant to a string. This is mainly used for debugging.
        Specified by:
        toString in interface DatabaseInstant
        Overrides:
        toString in class java.lang.Object
        Returns:
        a string representation of the instant.

      • toDebugString

        public static java.lang.String toDebugString​(long instant)

      • getValueAsLong

        public long getValueAsLong()
        These following methods are only intended to be called by an implementation of a log factory. All other uses of this object should only see it as a log instant.

      • getLogFilePosition

        public long getLogFilePosition()

      • getLogFileNumber

        public long getLogFileNumber()

      • readExternal

        public void readExternal​(java.io.ObjectInput oi)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException
        Read this in.
        Specified by:
        readExternal in interface java.io.Externalizable
        Throws:
        java.io.IOException - error reading from log stream
        java.lang.ClassNotFoundException - corrupted log stream

      • writeExternal

        public void writeExternal​(java.io.ObjectOutput oo)
                   throws java.io.IOException
        Write this out.
        Specified by:
        writeExternal in interface java.io.Externalizable
        Throws:
        java.io.IOException - error writing to log stream

      • getTypeFormatId

        public int getTypeFormatId()
        Get the formatID which corresponds to this class.
        Specified by:
        getTypeFormatId in interface TypedFormat
        Returns:
        the formatID of this class