ModSQL
Interface DatabaseIndex

All Superinterfaces:

DatabaseTableBase

All Known Implementing Classes:

IndexTable

public interface DatabaseIndex

extends DatabaseTableBase

Interface to be implemented by table indices.

An implementation of DatabaseTable returns objects of this type when requests are made to open an index on a specific column. It is possible for table classes to also implement DatabaseIndex and return "this" when asked for a specific index. ModSQL will never use more than one index for a specific table at one time, nor will it access the table through both an index and the table simultaneously.

Author:

chris.studholme@utoronto.ca

See Also:

DatabaseTable

Method Summary

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.

Methods inherited from interface ModSQL.DatabaseTableBase

afterLast, beforeFirst, close, commitUpdates, deleteRow, getObject, getRowCount, getRowId, isAfterLast, isBeforeFirst, next, updateObject

Method Detail

getDistinctCount

public long getDistinctCount()
                      throws DatabaseException

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

Returns:

number of distinct values

Throws:

DatabaseException - if a database-access error occurs

getNullCount

public long getNullCount()
                  throws DatabaseException

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

Returns:

number of null values

Throws:

DatabaseException - if a database-access error occurs

findNext

public boolean findNext(Object data)
                 throws DatabaseException

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.

Parameters:

data - desired data

Returns:

true if the new current row is valid; false otherwise

Throws:

DatabaseException - if a database-access error occurs