ModSQL
Class IndexTable_Sort

java.lang.Object
  |
  +--ModSQL.IndexTable
        |
        +--ModSQL.IndexTable_Sort

All Implemented Interfaces:

DatabaseIndex, DatabaseTableBase

class IndexTable_Sort

extends IndexTable

Implementation of DatabaseTable for tables that are indexed by the ModSQL driver.

This index can be accessed just as the original table is accessed. Access to the column that is indexed will be fast while access to other columns will be slower as data must be loaded from the original table.

Author:

chris.studholme@utoronto.ca

Field Summary

protected boolean	after_last
protected boolean	before_first
protected BufferedInputStream	buffer
protected static int	BUFFERSIZE
protected int	columnindex
protected int	columntype
protected long	current_count
protected int	current_entry
protected int	current_index
protected IndexTableEntry[]	entries
protected int	entries_to_read
protected FileInputStream	file
protected ObjectInputStream	istream
protected DatabaseTable	table
protected static int	TYPE
protected static int	VERSION

Constructor Summary

IndexTable_Sort(DatabaseTable table, String filename)
Constructor.

Method Summary

void	afterLast() Moves the table cursor to a position after the last row in the table.
void	beforeFirst() Moves the table cursor to a position before the first row in the table.
void	close() In some cases, it is desirable to immediately release a DatabaseTable's database and other resources instead of waiting for this to happen when it is automatically closed; the close method provides this immediate release.
void	commitUpdates() ModSQL will always call this method after performing a series of updateObject() calls on a particular row.
(package private) static void	createIndex(DatabaseManager tablemanager, String tablename, int columnindex) Create new index.
(package private) static void	createIndex(DatabaseManager tablemanager, String tablename, String columnname) Create new index.
(package private) static void	createIndex(DatabaseTable table, int columnindex) Create new index.
void	deleteRow() Delete the current row from the table and the underlying database.
protected void	finalize() Close index.
boolean	findNext(int column, Object data) Old version of findNext() above that requires a column index.
boolean	findNext(Object data) Finds the next row that has the specified data in the indexed column.
long	getDistinctCount() Returns the number of distinct values stored in the indexed column in the underlying table.
long	getNullCount() Returns the number of null values stored in the indexed column in the underlying table.
Object	getObject(int column) Get the value of a column in the current row as a Java object.
long	getRowCount() This method is expected to return the total number of rows in the database.
Object	getRowId() Get database specific rowid value.
boolean	isAfterLast() Determine if the table cursor is positioned after the last row in the table.
boolean	isBeforeFirst() Determine if the table cursor is positioned before the first row in the table.
boolean	next() A DatabaseTable is initially positioned before its first row; the first call to next makes the first row the current row; the second call makes the second row the current row, etc.
void	updateObject(int column, Object x) Update a column with an Object value.

Methods inherited from class ModSQL.IndexTable

getIndexFilename, isIndexAvailable, openIndex

Methods inherited from class java.lang.Object

, clone, equals, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait

Field Detail

TYPE

protected static final int TYPE

VERSION

protected static final int VERSION

BUFFERSIZE

protected static final int BUFFERSIZE

file

protected FileInputStream file

buffer

protected BufferedInputStream buffer

istream

protected ObjectInputStream istream

table

protected DatabaseTable table

columnindex

protected int columnindex

columntype

protected int columntype

entries

protected IndexTableEntry[] entries

entries_to_read

protected int entries_to_read

before_first

protected boolean before_first

after_last

protected boolean after_last

current_entry

protected int current_entry

current_index

protected int current_index

current_count

protected long current_count

Constructor Detail

IndexTable_Sort

public IndexTable_Sort(DatabaseTable table,
                       String filename)
                throws DatabaseException

Constructor. Open existing index.

Parameters:

table - open table to index

filename - path to index file

Throws:

DatabaseException - if there is a problem with the index

Method Detail

finalize

protected void finalize()

Close index.

Overrides:

finalize in class Object

close

public final void close()

Description copied from interface: DatabaseTableBase

In some cases, it is desirable to immediately release a DatabaseTable's database and other resources instead of waiting for this to happen when it is automatically closed; the close method provides this immediate release.

Note: A DatabaseTable is automatically closed by the Statement that generated it when that Statement is closed, re-executed, or is used to retrieve the next result from a sequence of multiple results. A DatabaseTable is also automatically closed when it is garbage collected.

Following copied from interface: ModSQL.DatabaseTableBase

Throws:

DatabaseException - if a database-access error occurs

getRowCount

public long getRowCount()

Description copied from interface: DatabaseTableBase

This method is expected to return the total number of rows in the database. This value is used by ModSQL for query optimization purposes. If the count cannot be easily determined, the database should return -1 to indicate that the count is unknown.

Following copied from interface: ModSQL.DatabaseTableBase

Returns:

number of rows in table, or -1 for unknown

Throws:

DatabaseException - if a database-access error occurs

getDistinctCount

public long getDistinctCount()

Description copied from interface: DatabaseIndex

Returns the number of distinct values stored in the indexed column in the underlying table. This method may return an approximation.

Following copied from interface: ModSQL.DatabaseIndex

Returns:

number of distinct values

Throws:

DatabaseException - if a database-access error occurs

getNullCount

public long getNullCount()

Description copied from interface: DatabaseIndex

Returns the number of null values stored in the indexed column in the underlying table. This method may return an approximation.

Following copied from interface: ModSQL.DatabaseIndex

Returns:

number of null values

Throws:

DatabaseException - if a database-access error occurs

next

public boolean next()
             throws DatabaseException

Description copied from interface: DatabaseTableBase

A DatabaseTable is initially positioned before its first row; the first call to next makes the first row the current row; the second call makes the second row the current row, etc.

Following copied from interface: ModSQL.DatabaseTableBase

Returns:

true if the new current row is valid; false if there are no more rows

Throws:

DatabaseException - if a database-access error occurs

findNext

public boolean findNext(Object data)
                 throws DatabaseException

Description copied from interface: DatabaseIndex

Finds the next row that has the specified data in the indexed column. Returns false if no such row could be found. The search always begins at the next row in the database and continues to the last row in the database.

Following copied from interface: ModSQL.DatabaseIndex

Parameters:

data - desired data

Returns:

true if the new current row is valid; false otherwise

Throws:

DatabaseException - if a database-access error occurs

findNext

public boolean findNext(int column,
                        Object data)
                 throws DatabaseException

Old version of findNext() above that requires a column index. Do not use this method directly.

Throws:

DatabaseException - if there is a problem with the index

deleteRow

public void deleteRow()
               throws DatabaseException

Description copied from interface: DatabaseTableBase

Delete the current row from the table and the underlying database. Cannot be called when on a newly inserted row.

Following copied from interface: ModSQL.DatabaseTableBase

Throws:

DatabaseException - if a database-access error occurs

isBeforeFirst

public boolean isBeforeFirst()

Description copied from interface: DatabaseTableBase

Determine if the table cursor is positioned before the first row in the table.

Following copied from interface: ModSQL.DatabaseTableBase

Returns:

true if before the first row, false otherwise

Throws:

DatabaseException - if a database-access error occurs

isAfterLast

public boolean isAfterLast()

Description copied from interface: DatabaseTableBase

Determine if the table cursor is positioned after the last row in the table.

Following copied from interface: ModSQL.DatabaseTableBase

Returns:

true if after the last row, false otherwise

Throws:

DatabaseException - if a database-access error occurs

beforeFirst

public void beforeFirst()
                 throws DatabaseException

Description copied from interface: DatabaseTableBase

Moves the table cursor to a position before the first row in the table. The next call to next() will set the cursor to the first row in the table (assuming the table has at least one row).

Following copied from interface: ModSQL.DatabaseTableBase

Throws:

DatabaseException - if a database-access error occurs

afterLast

public void afterLast()
               throws DatabaseException

Description copied from interface: DatabaseTableBase

Moves the table cursor to a position after the last row in the table. All calls to next() will return false until beforeFirst() is called to reset the table.

Following copied from interface: ModSQL.DatabaseTableBase

Throws:

DatabaseException - if a database-access error occurs

getRowId

public Object getRowId()
                throws DatabaseException

Description copied from interface: DatabaseTableBase

Get database specific rowid value. This value can be later used with absolute() to seek to a specific row.

Following copied from interface: ModSQL.DatabaseTableBase

Returns:

object representing current row, or null if no current row

Throws:

DatabaseException - if a database-access error occurs

getObject

public Object getObject(int column)
                 throws DatabaseException

Description copied from interface: DatabaseTableBase

Get the value of a column in the current row as a Java object.

This method will return the value of the given column as a Java object. The type of the Java object will be the default Java Object type corresponding to the column's SQL type, following the mapping specified in the JDBC spec.

This method may also be used to read datatabase specific abstract data types.

Following copied from interface: ModSQL.DatabaseTableBase

Parameters:

column - the first column is 1, the second is 2, ...

Returns:

an Object holding the column value

Throws:

DatabaseException - if a database-access error occurs

updateObject

public void updateObject(int column,
                         Object x)
                  throws DatabaseException

Description copied from interface: DatabaseTableBase

Update a column with an Object value.

The updateObject() method is used to update column values in the current row, or a newly inserted row.

Following copied from interface: ModSQL.DatabaseTableBase

Parameters:

column - the first column is 1, the second is 2, ...

x - the new column value

Throws:

DatabaseException - if a database-access error occurs

commitUpdates

public void commitUpdates()
                   throws DatabaseException

Description copied from interface: DatabaseTableBase

ModSQL will always call this method after performing a series of updateObject() calls on a particular row. If this call is not received before the row is changed or the table is closed, the changes made by updateObject() should be discarded. In the case where addRow() was called before the updateObject() calls, the new row can be discarded as well.

Following copied from interface: ModSQL.DatabaseTableBase

Throws:

DatabaseException - if a database-access error occurs

createIndex

static void createIndex(DatabaseManager tablemanager,
                        String tablename,
                        String columnname)
                 throws SQLException

Create new index.

Parameters:

tablemanager - active table manager

tablename - name of table to index

columnname - name of column to index

Throws:

SQLException - if there is a problem creating the index

createIndex

static void createIndex(DatabaseManager tablemanager,
                        String tablename,
                        int columnindex)
                 throws SQLException

Create new index.

Parameters:

tablemanager - active table manager

tablename - name of table to index

columnindex - index of column to index

Throws:

SQLException - if there is a problem creating the index

createIndex

static void createIndex(DatabaseTable table,
                        int columnindex)
                 throws SQLException

Create new index.

Parameters:

table - open table to index

columnindex - index of column to index

Throws:

SQLException - if there is a problem creating the index