Interface DatabaseInstant

  • All Superinterfaces:
    java.io.Serializable
    All Known Subinterfaces:
    LogInstant
    All Known Implementing Classes:
    LogCounter

    public interface DatabaseInstant
    extends java.io.Serializable
    A DatabaseInstant is a quantity which the database associates with events to collate them. This interface is used in the column SYS.SYSSYNCINSTANTS.INSTANT.

    Assume a database associates a DatabaseInstant to an event E1. We call this I(E1). Also assume the same Database associates a DatabaseInstant to a second event E2. We call this I(E2). By definition

    1. If I(E1) < I(E2) event E1 occurred before event E2
    2. If I(E2) = I(E2) event E1 is the same event as E2
    3. If I(E1) > I(E2) event E1 occurred after event E2

    It is not meaningful to compare a DatabaseInstant from one database with a DatabaseInstant from another. The result of such a comparison is undefined. Because a database may construct, store and compare huge numbers of DatabaseInstants, this interface does not require an implementation to notice when a caller compares a DatabaseInstants from different databases.

    Any implementation of this interface must implement value equality, thus implementing equals() and hashCode() methods.

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      boolean equals​(java.lang.Object other)
      Return true if this DatabaseInstant equals DatabaseInstant from the same database.
      boolean lessThan​(DatabaseInstant other)
      Return true if this DatabaseInstant is before another DatabaseInstant from the same database.
      DatabaseInstant next()
      Return the next higher DatabaseInstant.
      DatabaseInstant prior()
      Return the next lower DatabaseInstant.
      java.lang.String toString()
      Convert the database instant to a string.
    • Method Detail

      • lessThan

        boolean lessThan​(DatabaseInstant other)
        Return true if this DatabaseInstant is before another DatabaseInstant from the same database.
        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

        boolean equals​(java.lang.Object other)
        Return true if this DatabaseInstant equals DatabaseInstant from the same database.
        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

        DatabaseInstant next()
        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.
        Returns:
        the next possible DatabaseInstant
      • prior

        DatabaseInstant prior()
        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.
        Returns:
        the prior possible DatabaseInstant
      • toString

        java.lang.String toString()
        Convert the database instant to a string. This is mainly used for debugging.
        Overrides:
        toString in class java.lang.Object
        Returns:
        a string representation of the instant.