Interface DatabaseInstant
- All Superinterfaces:
Serializable
- All Known Subinterfaces:
LogInstant
- All Known Implementing Classes:
LogCounter
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
- If I(E1) < I(E2) event E1 occurred before event E2
- If I(E2) = I(E2) event E1 is the same event as E2
- 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.
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Method Summary
Modifier and TypeMethodDescriptionboolean
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.next()
Return the next higher DatabaseInstant.prior()
Return the next lower DatabaseInstant.toString()
Convert the database instant to a string.
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Method Details
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lessThan
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.
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equals
Return true if this DatabaseInstant equals DatabaseInstant from the same database. -
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
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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
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toString
String toString()Convert the database instant to a string. This is mainly used for debugging.
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