Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.iapi.store.access.DatabaseInstant

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.

Method Summary

Modifier and Type	Method and Description
public boolean	Returns: the comparison result. If 'other' is from another database the result is undefined. equals(Object a DatabaseInstant from the same database as this. other) Return true if this DatabaseInstant equals DatabaseInstant from the same database.
public boolean	Returns: the comparison result. If 'other' is from another database the result is undefined. lessThan(DatabaseInstant a DatabaseInstant from the same database as this. other) Return true if this DatabaseInstant is before another DatabaseInstant from the same database.
public DatabaseInstant	Returns: the next possible DatabaseInstant next() Return the next higher DatabaseInstant.
public DatabaseInstant	Returns: the prior possible DatabaseInstant prior() Return the next lower DatabaseInstant.
public String	Returns: a string representation of the instant. toString() Convert the database instant to a string.

Method Detail

equals	back to summary
public boolean equals(Object other) Return true if this DatabaseInstant equals DatabaseInstant from the same database. Parameters other:Object a DatabaseInstant from the same database as this. Returns:boolean the comparison result. If 'other' is from another database the result is undefined.

equals

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public boolean equals(Object other)

Return true if this DatabaseInstant equals DatabaseInstant from the same database.

Parameters

other:Object: a DatabaseInstant from the same database as this.

Returns:boolean

the comparison result. If 'other' is from another database the result is undefined.

lessThan	back to summary
public boolean lessThan(DatabaseInstant other) Return true if this DatabaseInstant is before another DatabaseInstant from the same database. Parameters other:DatabaseInstant a DatabaseInstant from the same database as this. Returns:boolean the comparison result. If 'other' is from another database the result is undefined.

lessThan

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public boolean lessThan(DatabaseInstant other)

Return true if this DatabaseInstant is before another DatabaseInstant from the same database.

Parameters

other:DatabaseInstant: a DatabaseInstant from the same database as this.

Returns:boolean

the comparison result. If 'other' is from another database the result is undefined.

next	back to summary
public 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:DatabaseInstant the next possible DatabaseInstant

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public 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:DatabaseInstant: the next possible DatabaseInstant

prior	back to summary
public 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:DatabaseInstant the prior possible DatabaseInstant

prior

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public 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:DatabaseInstant: the prior possible DatabaseInstant

toString	back to summary
public String toString() Convert the database instant to a string. This is mainly used for debugging. Returns:String a string representation of the instant.

toString

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public String toString()

Convert the database instant to a string. This is mainly used for debugging.

Returns:String: a string representation of the instant.

public Interface DatabaseInstant

Method Summary

Method Detail