com.mckoi.database.VirtualTable Maven / Gradle / Ivy
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/**
* com.mckoi.database.VirtualTable 08 Mar 1998
*
* Mckoi SQL Database ( http://www.mckoi.com/database )
* Copyright (C) 2000, 2001, 2002 Diehl and Associates, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* Version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License Version 2 for more details.
*
* You should have received a copy of the GNU General Public License
* Version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Change Log:
*
*
*/
package com.mckoi.database;
import com.mckoi.util.IntegerVector;
import com.mckoi.util.BlockIntegerList;
/**
* 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
*/
public class VirtualTable extends JoinedTable {
/**
* Array of IntegerVectors that represent the rows taken from the given
* parents.
*/
protected IntegerVector[] row_list;
/**
* The number of rows in the table.
*/
private int row_count;
/**
* Helper function for the constructor.
*/
protected void init(Table[] tables) {
super.init(tables);
int table_count = tables.length;
row_list = new IntegerVector[table_count];
for (int i = 0; i < table_count; ++i) {
row_list[i] = new IntegerVector();
}
}
/**
* The Constructor. It is constructed with a list of tables that this
* virtual table is a sub-set or join of.
*/
VirtualTable(Table[] tables) {
super(tables);
}
VirtualTable(Table table) {
super(table);
}
protected VirtualTable() {
super();
}
/**
* Returns the list of IntegerVector that represents the rows that this
* VirtualTable references.
*/
protected IntegerVector[] getReferenceRows() {
return row_list;
}
/**
* Returns the number of rows stored in the table.
*/
public int getRowCount() {
return row_count;
}
/**
* Sets the rows in this table. We should search for the
* 'table' in the 'reference_list' however we don't for efficiency.
*/
void set(Table table, IntegerVector rows) {
row_list[0] = new IntegerVector(rows);
row_count = rows.size();
}
/**
* This is used in a join to set a list or joined rows and tables. The
* 'tables' array should be an exact mirror of the 'reference_list'. The
* IntegerVector[] array contains the rows to add for each respective table.
* The given IntegerVector objects should have identical lengths.
*/
void set(Table[] tables, IntegerVector[] rows) {
for (int i = 0; i < tables.length; ++i) {
row_list[i] = new IntegerVector(rows[i]);
}
if (rows.length > 0) {
row_count = rows[0].size();
}
}
/**
* Sets the rows in this table as above, but uses a BlockIntegerList as an
* argument instead.
*/
void set(Table table, BlockIntegerList rows) {
row_list[0] = new IntegerVector(rows);
row_count = rows.size();
}
/**
* Sets the rows in this table as above, but uses a BlockIntegerList array
* as an argument instead.
*/
void set(Table[] tables, BlockIntegerList[] rows) {
for (int i = 0; i < tables.length; ++i) {
row_list[i] = new IntegerVector(rows[i]);
}
if (rows.length > 0) {
row_count = rows[0].size();
}
}
// ---------- Implemented from JoinedTable ----------
protected int resolveRowForTableAt(int row_number, int table_num) {
return row_list[table_num].intAt(row_number);
}
protected void resolveAllRowsForTableAt(
IntegerVector row_set, int table_num) {
IntegerVector cur_row_list = row_list[table_num];
for (int n = row_set.size() - 1; n >= 0; --n) {
int aa = row_set.intAt(n);
int bb = cur_row_list.intAt(aa);
row_set.setIntAt(bb, n);
}
}
}