com.mckoi.database
Class VirtualTable

java.lang.Object
  com.mckoi.database.Table
      com.mckoi.database.JoinedTable
          com.mckoi.database.VirtualTable

All Implemented Interfaces:

TableDataSource

public class VirtualTable
extends JoinedTable

A VirtualTable is a representation of a table whose rows are actually physically stored in another table. In other words, this table just stores pointers to rows in other tables.

We use the VirtualTable to represent temporary tables created from select, join, etc operations.

An important note about VirtualTables: When we perform a 'select' operation on a virtual table, unlike a DataTable that permanently stores information about column cell relations, we must resolve column relations between the sub-set at select time. This involves asking the tables parent(s) for a scheme to describe relations in a sub-set.

Author:

Tobias Downer

Field Summary

protected IntegerVector[]

row_list Array of IntegerVectors that represent the rows taken from the given parents.

Fields inherited from class com.mckoi.database.JoinedTable

column_filter, column_scheme, column_table, reference_list

Fields inherited from class com.mckoi.database.Table

DEBUG_QUERY

Constructor Summary

protected

VirtualTable()

Method Summary

protected IntegerVector[]	getReferenceRows() Returns the list of IntegerVector that represents the rows that this VirtualTable references.
int	getRowCount() Returns the number of rows stored in the table.
protected void	init(Table[] tables) Helper function for the constructor.
protected void	resolveAllRowsForTableAt(IntegerVector row_set, int table_num) Given an IntegerVector that represents a list of pointers to rows in this table, this resolves the rows to row indexes in the given parent table.
protected int	resolveRowForTableAt(int row_number, int table_num) Given a row and a table index (to a parent reference table), this will return the row index in the given parent table for the given row.

Methods inherited from class com.mckoi.database.JoinedTable

findFieldName, getCellContents, getColumnCount, getDatabase, getDataTableDef, getReferenceTables, getResolvedVariable, hasRootsLocked, lockRoot, printGraph, rowEnumeration, unlockRoot

Methods inherited from class com.mckoi.database.Table

all, allColumnMatchesValue, any, columnContainsCell, columnContainsValue, columnMatchesValue, columnMerge, compareCells, Debug, distinct, distinct, dumpTo, emptySelect, exhaustiveSelect, fastFindFieldName, getColumnDefAt, getColumnScheme, getFirstCellContent, getFirstCellContent, getLastCellContent, getLastCellContent, getSingleCellContent, getSingleCellContent, getSystem, getTableAccessState, getTTypeForColumn, getTTypeForColumn, join, orderByColumn, orderByColumn, orderByColumn, orderByColumns, orderedRowList, outside, rangeSelect, selectAll, selectAll, selectFirst, selectLast, selectRange, selectRest, simpleJoin, simpleSelect, singleRowSelect, toMap, toString, union

Methods inherited from class java.lang.Object

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

Field Detail

row_list

protected IntegerVector[] row_list

Array of IntegerVectors that represent the rows taken from the given parents.

Constructor Detail

VirtualTable

protected VirtualTable()

Method Detail

init

protected void init(Table[] tables)

Helper function for the constructor.

Overrides:

init in class JoinedTable

getReferenceRows

protected IntegerVector[] getReferenceRows()

Returns the list of IntegerVector that represents the rows that this VirtualTable references.

getRowCount

public int getRowCount()

Returns the number of rows stored in the table.

Specified by:

getRowCount in interface TableDataSource

Specified by:

getRowCount in class Table

resolveRowForTableAt

protected int resolveRowForTableAt(int row_number,
                                   int table_num)

Description copied from class: JoinedTable

Given a row and a table index (to a parent reference table), this will return the row index in the given parent table for the given row.

Specified by:

resolveRowForTableAt in class JoinedTable

resolveAllRowsForTableAt

protected void resolveAllRowsForTableAt(IntegerVector row_set,
                                        int table_num)

Description copied from class: JoinedTable

Given an IntegerVector that represents a list of pointers to rows in this table, this resolves the rows to row indexes in the given parent table. This method changes the 'row_set' IntegerVector object.

Specified by:

resolveAllRowsForTableAt in class JoinedTable