/**
* com.mckoi.database.BlindSearch 14 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 java.io.*;
import java.util.Arrays;
import java.util.Comparator;
import com.mckoi.util.IntegerVector;
import com.mckoi.util.BlockIntegerList;
/**
* This is a scheme that performs a blind search of a given set. It records
* no information about how a set element relates to the rest. It blindly
* searches through the set to find elements that match the given criteria.
* <p>
* This scheme performs badly on large sets because it requires that the
* database is queried often for information. However since it records no
* information about the set, memory requirements are non-existant.
* <p>
* This scheme should not be used for anything other than small domain sets
* because the performance suffers very badly with larger sets. It is ideal
* for small domain sets because of its no memory overhead. For any select
* operation this algorithm must check every element in the set.
*
* @author Tobias Downer
*/
public final class BlindSearch extends SelectableScheme {
/**
* The Constructor.
*/
public BlindSearch(TableDataSource table, int column) {
super(table, column);
}
/**
* This scheme doesn't take any notice of insertions or removals.
*/
public void insert(int row) {
if (isImmutable()) {
throw new Error("Tried to change an immutable scheme.");
}
}
/**
* This scheme doesn't take any notice of insertions or removals.
*/
public void remove(int row) {
if (isImmutable()) {
throw new Error("Tried to change an immutable scheme.");
}
}
/**
* Reads the entire state of the scheme from the input stream.
* This is a trivial case for BlindSearch which doesn't require any
* data to be stored.
*/
public void readFrom(InputStream in) throws IOException {
}
/**
* Writes the entire state of the scheme to the output stream.
* This is a trivial case for BlindSearch which doesn't require any
* data to be stored.
*/
public void writeTo(OutputStream out) throws IOException {
}
/**
* Returns an exact copy of this scheme including any optimization
* information. The copied scheme is identical to the original but does not
* share any parts. Modifying any part of the copied scheme will have no
* effect on the original and vice versa.
*/
public SelectableScheme copy(TableDataSource table, boolean immutable) {
// Return a fresh object. This implementation has no state so we can
// ignore the 'immutable' flag.
return new BlindSearch(table, getColumn());
}
/**
* Disposes and invalidates the BlindSearch.
*/
public void dispose() {
// Nothing to do!
}
/**
* Selection methods for obtaining various sub-sets of information from the
* set.
*/
/**
* We implement an insert sort algorithm here. Each new row is inserted
* into our row vector at the sorted corrent position.
* The algorithm assumes the given vector is already sorted. We then just
* subdivide the set until we can insert at the required position.
*/
private int search(TObject ob, IntegerVector vec, int lower, int higher) {
if (lower >= higher) {
if (ob.compareTo(getCellContents(vec.intAt(lower))) > 0) {
return lower + 1;
}
else {
return lower;
}
}
int mid = lower + ((higher - lower) / 2);
int comp_result = ob.compareTo(getCellContents(vec.intAt(mid)));
if (comp_result == 0) {
return mid;
}
else if (comp_result < 0) {
return search(ob, vec, lower, mid - 1);
}
else {
return search(ob, vec, mid + 1, higher);
}
}
/**
* Searches for a given TObject (ob) in the row list between the two
* bounds. This will return the highest row of the set of values that are
* equal to 'ob'.
* <p>
* This returns the place to insert ob into the vector, it should not be
* used to determine if ob is in the list or not.
*/
private int highestSearch(TObject ob, IntegerVector vec,
int lower, int higher) {
if ((higher - lower) <= 5) {
// Start from the bottom up until we find the highest val
for (int i = higher; i >= lower; --i) {
int res = ob.compareTo(getCellContents(vec.intAt(i)));
if (res >= 0) {
return i + 1;
}
}
// Didn't find return lowest
return lower;
}
int mid = (lower + higher) / 2;
int comp_result = ob.compareTo(getCellContents(vec.intAt(mid)));
if (comp_result == 0) {
// We know the bottom is between 'mid' and 'higher'
return highestSearch(ob, vec, mid, higher);
}
else if (comp_result < 0) {
return highestSearch(ob, vec, lower, mid - 1);
}
else {
return highestSearch(ob, vec, mid + 1, higher);
}
}
private void doInsertSort(IntegerVector vec, int row) {
int list_size = vec.size();
if (list_size == 0) {
vec.addInt(row);
}
else {
int point = highestSearch(getCellContents(row), vec, 0, list_size - 1);
if (point == list_size) {
vec.addInt(row);
}
else {
vec.insertIntAt(row, point);
}
}
}
public IntegerVector selectAll() {
IntegerVector row_list = new IntegerVector(getTable().getRowCount());
RowEnumeration e = getTable().rowEnumeration();
while (e.hasMoreRows()) {
doInsertSort(row_list, e.nextRowIndex());
}
return row_list;
}
public IntegerVector selectRange(SelectableRange range) {
int set_size = getTable().getRowCount();
// If no items in the set return an empty set
if (set_size == 0) {
return new IntegerVector(0);
}
return selectRange(new SelectableRange[] { range } );
}
public IntegerVector selectRange(SelectableRange[] ranges) {
int set_size = getTable().getRowCount();
// If no items in the set return an empty set
if (set_size == 0) {
return new IntegerVector(0);
}
RangeChecker checker = new RangeChecker(ranges);
return checker.resolve();
}
// ---------- Inner classes ----------
/**
* Object used to during range check loop.
*/
final class RangeChecker {
/**
* The sorted list of all items in the set created as a cache for finding
* the first and last values.
*/
private IntegerVector sorted_set = null;
/**
* The list of flags for each check in the range.
* Either 0 for no check, 1 for < or >, 2 for <= or >=.
*/
private byte[] lower_flags;
private byte[] upper_flags;
/**
* The TObject objects to check against.
*/
private TObject[] lower_cells;
private TObject[] upper_cells;
/**
* Constructs the checker.
*/
public RangeChecker(SelectableRange[] ranges) {
int size = ranges.length;
lower_flags = new byte[size];
upper_flags = new byte[size];
lower_cells = new TObject[size];
upper_cells = new TObject[size];
for (int i = 0; i < ranges.length; ++i) {
setupRange(i, ranges[i]);
}
}
private void resolveSortedSet() {
if (sorted_set == null) {
// System.out.println("SLOW RESOLVE SORTED SET ON BLIND SEARCH.");
sorted_set = selectAll();
}
}
/**
* Resolves a cell.
*/
private TObject resolveCell(TObject ob) {
if (ob == SelectableRange.FIRST_IN_SET) {
resolveSortedSet();
return getCellContents(sorted_set.intAt(0));
}
else if (ob == SelectableRange.LAST_IN_SET) {
resolveSortedSet();
return getCellContents(sorted_set.intAt(sorted_set.size() - 1));
}
else {
return ob;
}
}
/**
* Set up a range.
*/
public void setupRange(int i, SelectableRange range) {
TObject l = range.getStart();
byte lf = range.getStartFlag();
TObject u = range.getEnd();
byte uf = range.getEndFlag();
// Handle lower first
if (l == SelectableRange.FIRST_IN_SET &&
lf == SelectableRange.FIRST_VALUE) {
// Special case no lower check
lower_flags[i] = 0;
}
else {
if (lf == SelectableRange.FIRST_VALUE) {
lower_flags[i] = 2; // >=
}
else if (lf == SelectableRange.AFTER_LAST_VALUE) {
lower_flags[i] = 1; // >
}
else {
throw new Error("Incorrect lower flag.");
}
lower_cells[i] = resolveCell(l);
}
// Now handle upper
if (u == SelectableRange.LAST_IN_SET &&
uf == SelectableRange.LAST_VALUE) {
// Special case no upper check
upper_flags[i] = 0;
}
else {
if (uf == SelectableRange.LAST_VALUE) {
upper_flags[i] = 2; // <=
}
else if (uf == SelectableRange.BEFORE_FIRST_VALUE) {
upper_flags[i] = 1; // <
}
else {
throw new Error("Incorrect upper flag.");
}
upper_cells[i] = resolveCell(u);
}
}
/**
* Resolves the ranges.
*/
public IntegerVector resolve() {
// The idea here is to only need to scan the column once to find all
// the cells that meet our criteria.
IntegerVector ivec = new IntegerVector();
RowEnumeration e = getTable().rowEnumeration();
int compare_tally = 0;
int size = lower_flags.length;
while (e.hasMoreRows()) {
int row = e.nextRowIndex();
// For each range
range_set:
for (int i = 0; i < size; ++i) {
boolean result = true;
byte lf = lower_flags[i];
if (lf != 0) {
++compare_tally;
TObject v = getCellContents(row);
int compare = lower_cells[i].compareTo(v);
if (lf == 1) { // >
result = (compare < 0);
}
else if (lf == 2) { // >=
result = (compare <= 0);
}
else {
throw new Error("Incorrect flag.");
}
}
if (result) {
byte uf = upper_flags[i];
if (uf != 0) {
++compare_tally;
TObject v = getCellContents(row);
int compare = upper_cells[i].compareTo(v);
if (uf == 1) { // <
result = (compare > 0);
}
else if (uf == 2) { // >=
result = (compare >= 0);
}
else {
throw new Error("Incorrect flag.");
}
}
// Pick this row
if (result) {
doInsertSort(ivec, row);
break range_set;
}
}
}
}
// System.out.println("Blind Search compare tally: " + compare_tally);
return ivec;
}
}
}
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