Class AutoincrementCounter
java.lang.Object
org.apache.derby.impl.sql.execute.AutoincrementCounter
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
Fields -
Constructor Summary
ConstructorsConstructorDescriptionAutoincrementCounter
(Long start, long increment, long finalValue, String s, String t, String c, int position) constructor -
Method Summary
Modifier and TypeMethodDescriptionvoid
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
get the column position in the table for which this counter has been created.get the current value of the counter.return the identity of the counter.get the start valuestatic String
makeIdentity
(String s, String t, String c) make a unique key for the counter.static String
make a unique key for the counter.void
reset
(boolean begin) reset to the counter to the beginning or the end.toString()
long
update()
update the counter to its next value.long
update
(long t) update the counter.
-
Field Details
-
start
-
increment
private long increment -
identity
-
finalValue
private long finalValue -
schemaName
-
tableName
-
columnName
-
counter
private long counter -
columnPosition
private int columnPosition -
initialized
private boolean initialized
-
-
Constructor Details
-
AutoincrementCounter
public AutoincrementCounter(Long start, long increment, long finalValue, String s, String t, 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 resets
-t
-c
-
-
-
Method Details
-
makeIdentity
make a unique key for the counter. -
makeIdentity
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
update the counter to its next value.- Throws:
StandardException
- if the counter has not yet been initialized and the Start value is NULL.
-
getCurrentValue
get the current value of the counter. An uninitialized counter means the current value is NULL. -
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 usedd
- 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
get the start value- Returns:
- the initial value of the counter
-
toString
-