ModSQL
Class IndexTable

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

All Implemented Interfaces:

DatabaseIndex, DatabaseTableBase

Direct Known Subclasses:

IndexTable_Hash, IndexTable_Sort

abstract class IndexTable

extends Object

implements DatabaseIndex

Abstract base class for built-in table indexing classes.

Author:

chris.studholme@utoronto.ca

Constructor Summary

(package private)

IndexTable()

Method Summary

protected static String	getIndexFilename(String tablename, String columnname) Return an appropriate filename for an index of the specified column of the specified table.
static boolean	isIndexAvailable(String filename) Check if the specified index file is available.
(package private) static IndexTable	openIndex(DatabaseTable table, String columnname) Attempt to open index on the specified column of an open table.

Methods inherited from class java.lang.Object

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

Methods inherited from interface ModSQL.DatabaseIndex

findNext, getDistinctCount, getNullCount

Methods inherited from interface ModSQL.DatabaseTableBase

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

Constructor Detail

IndexTable

IndexTable()

Method Detail

openIndex

static IndexTable openIndex(DatabaseTable table,
                            String columnname)
                     throws DatabaseException

Attempt to open index on the specified column of an open table.

Parameters:

table - open table

columnname - name of indexed column

Returns:

index on column, or null if index not available

Throws:

DatabaseException - if there is a problem with the index

isIndexAvailable

public static boolean isIndexAvailable(String filename)

Check if the specified index file is available.

Parameters:

filename - full path to index file

Returns:

true if the file is there and readable

getIndexFilename

protected static String getIndexFilename(String tablename,
                                         String columnname)

Return an appropriate filename for an index of the specified column of the specified table. This method will generate a single character hash code ([A-P]) for the index and return a filename like:
/data/index/C/table.column

Note:

• /data/index is the base index directory
• C is the computed hash code
• table is the name of the table
• column is the name of the column

This method will ensure that the directory where the index data will be stored exists.

Parameters:

tablename - name of table to index

columnname - name of column to index

Returns:

full qualified path name where index data should be stored