org.apache.derby.impl.sql.execute

Class AutoincrementCounter

java.lang.Object

org.apache.derby.impl.sql.execute.AutoincrementCounter

public class AutoincrementCounter
extends java.lang.Object

AutoincrementCounter is a not so general counter for the specific purposes of autoincrement columns. It can be thought of as an in-memory autoincrement column. The counting or incrementing is done in fashion identical to the AUTOINCREMENTVALUE in SYSCOLUMNS.

To create a counter, the user must call the constructor with a start value, increment and optionally a final value. In addition the caller must specify the schema name, table name and column name uniquely identifying the counter.

When a counter is created it is in an invalid state-- to initialize it, the user must call either update or reset(false). The value of a counter can be changed by either calling reset or update.

Constructor Summary

Constructors

Constructor and Description
AutoincrementCounter(java.lang.Long start, long increment, long finalValue, java.lang.String s, java.lang.String t, java.lang.String c, int position) constructor

Method Summary

Modifier and Type	Method and Description
void	flushToDisk(TransactionController tc, DataDictionary dd, UUID tableUUID) flush a counter to disk; i.e write the current value of the counter into the row in SYSCOLUMNS.
int	getColumnPosition() get the column position in the table for which this counter has been created.
java.lang.Long	getCurrentValue() get the current value of the counter.
java.lang.String	getIdentity() return the identity of the counter.
java.lang.Long	getStartValue() get the start value
static java.lang.String	makeIdentity(java.lang.String s, java.lang.String t, java.lang.String c) make a unique key for the counter.
static java.lang.String	makeIdentity(TableDescriptor td, ColumnDescriptor cd) make a unique key for the counter.
void	reset(boolean begin) reset to the counter to the beginning or the end.
java.lang.String	toString()
long	update() update the counter to its next value.
long	update(long t) update the counter.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

AutoincrementCounter

public AutoincrementCounter(java.lang.Long start,
                            long increment,
                            long finalValue,
                            java.lang.String s,
                            java.lang.String t,
                            java.lang.String c,
                            int position)

constructor

Parameters:

start - The start value of the counter; is a java object as it can also be null.

increment - how much to increment the counter by.

finalValue - the finalvalue of the counter. used by reset

s -

t -

c -

Method Detail

makeIdentity

public static java.lang.String makeIdentity(java.lang.String s,
                                            java.lang.String t,
                                            java.lang.String c)

make a unique key for the counter.

makeIdentity

public static java.lang.String makeIdentity(TableDescriptor td,
                                            ColumnDescriptor cd)

make a unique key for the counter.

reset

public void reset(boolean begin)

reset to the counter to the beginning or the end.

Parameters:

begin - if TRUE reset to beginning and mark it uninitialized.

update

public long update(long t)

update the counter.

Parameters:

t - update the counter to this value.

update

public long update()
            throws StandardException

update the counter to its next value.

Throws:

StandardException - if the counter has not yet been initialized and the Start value is NULL.

getCurrentValue

public java.lang.Long getCurrentValue()

get the current value of the counter. An uninitialized counter means the current value is NULL.

getIdentity

public java.lang.String getIdentity()

return the identity of the counter.

flushToDisk

public void flushToDisk(TransactionController tc,
                        DataDictionary dd,
                        UUID tableUUID)
                 throws StandardException

flush a counter to disk; i.e write the current value of the counter into the row in SYSCOLUMNS.

Parameters:

tc - TransactionController to use

dd - DataDictionary to use.

tableUUID - I might have the table name but I need more information

Throws:

StandardException - standard Derby exception.

getColumnPosition

public int getColumnPosition()

get the column position in the table for which this counter has been created.

Returns:

the position of the corresponding column in the table (1-based)

getStartValue

public java.lang.Long getStartValue()

get the start value

Returns:

the initial value of the counter

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object