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

java.lang.Object
  extended by 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.


Field Summary
private  java.lang.String columnName
           
private  int columnPosition
           
private  long counter
           
private  long finalValue
           
private  java.lang.String identity
           
private  long increment
           
private  boolean initialized
           
private  java.lang.String schemaName
           
private  java.lang.Long start
           
private  java.lang.String tableName
           
 
Constructor Summary
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
 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
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

start

private java.lang.Long start

increment

private long increment

identity

private java.lang.String identity

finalValue

private long finalValue

schemaName

private java.lang.String schemaName

tableName

private java.lang.String tableName

columnName

private java.lang.String columnName

counter

private long counter

columnPosition

private int columnPosition

initialized

private boolean initialized
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

Built on Thu 2011-03-10 11:54:14+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.