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/*
* Copyright 2004-2010 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.index;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import org.h2.engine.Constants;
import org.h2.engine.Session;
import org.h2.engine.UndoLogRecord;
import org.h2.message.DbException;
import org.h2.result.Row;
import org.h2.result.SearchRow;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.RegularTable;
import org.h2.util.New;
/**
* The scan index is not really an 'index' in the strict sense, because it can
* not be used for direct lookup. It can only be used to iterate over all rows
* of a table. Each regular table has one such object, even if no primary key or
* indexes are defined.
*/
public class ScanIndex extends BaseIndex {
private long firstFree = -1;
private ArrayList rows = New.arrayList();
private RegularTable tableData;
private int rowCountDiff;
private HashMap sessionRowCount;
private HashSet delta;
private long rowCount;
public ScanIndex(RegularTable table, int id, IndexColumn[] columns, IndexType indexType) {
initBaseIndex(table, id, table.getName() + "_DATA", columns, indexType);
if (database.isMultiVersion()) {
sessionRowCount = New.hashMap();
}
tableData = table;
}
public void remove(Session session) {
truncate(session);
}
public void truncate(Session session) {
rows = New.arrayList();
firstFree = -1;
if (tableData.getContainsLargeObject() && tableData.isPersistData()) {
database.getLobStorage().removeAllForTable(table.getId());
}
tableData.setRowCount(0);
rowCount = 0;
rowCountDiff = 0;
if (database.isMultiVersion()) {
sessionRowCount.clear();
}
}
public String getCreateSQL() {
return null;
}
public void close(Session session) {
// nothing to do
}
public Row getRow(Session session, long key) {
return rows.get((int) key);
}
public void add(Session session, Row row) {
// in-memory
if (firstFree == -1) {
int key = rows.size();
row.setKey(key);
rows.add(row);
} else {
long key = firstFree;
Row free = rows.get((int) key);
firstFree = free.getKey();
row.setKey(key);
rows.set((int) key, row);
}
row.setDeleted(false);
if (database.isMultiVersion()) {
if (delta == null) {
delta = New.hashSet();
}
boolean wasDeleted = delta.remove(row);
if (!wasDeleted) {
delta.add(row);
}
incrementRowCount(session.getId(), 1);
}
rowCount++;
}
public void commit(int operation, Row row) {
if (database.isMultiVersion()) {
if (delta != null) {
delta.remove(row);
}
incrementRowCount(row.getSessionId(), operation == UndoLogRecord.DELETE ? 1 : -1);
}
}
private void incrementRowCount(int sessionId, int count) {
if (database.isMultiVersion()) {
Integer id = sessionId;
Integer c = sessionRowCount.get(id);
int current = c == null ? 0 : c.intValue();
sessionRowCount.put(id, current + count);
rowCountDiff += count;
}
}
public void remove(Session session, Row row) {
// in-memory
if (!database.isMultiVersion() && rowCount == 1) {
rows = New.arrayList();
firstFree = -1;
} else {
Row free = new Row(null, 1);
free.setKey(firstFree);
long key = row.getKey();
rows.set((int) key, free);
firstFree = key;
}
if (database.isMultiVersion()) {
// if storage is null, the delete flag is not yet set
row.setDeleted(true);
if (delta == null) {
delta = New.hashSet();
}
boolean wasAdded = delta.remove(row);
if (!wasAdded) {
delta.add(row);
}
incrementRowCount(session.getId(), -1);
}
rowCount--;
}
public Cursor find(Session session, SearchRow first, SearchRow last) {
return new ScanCursor(session, this, database.isMultiVersion());
}
public double getCost(Session session, int[] masks) {
return tableData.getRowCountApproximation() + Constants.COST_ROW_OFFSET;
}
public long getRowCount(Session session) {
if (database.isMultiVersion()) {
Integer i = sessionRowCount.get(session.getId());
long count = i == null ? 0 : i.intValue();
count += rowCount;
count -= rowCountDiff;
return count;
}
return rowCount;
}
/**
* Get the next row that is stored after this row.
*
* @param session the session
* @param row the current row or null to start the scan
* @return the next row or null if there are no more rows
*/
Row getNextRow(Session session, Row row) {
long key;
if (row == null) {
key = -1;
} else {
key = row.getKey();
}
while (true) {
key++;
if (key >= rows.size()) {
return null;
}
row = rows.get((int) key);
if (!row.isEmpty()) {
return row;
}
}
}
public int getColumnIndex(Column col) {
// the scan index cannot use any columns
return -1;
}
public void checkRename() {
throw DbException.getUnsupportedException("SCAN");
}
public boolean needRebuild() {
return false;
}
public boolean canGetFirstOrLast() {
return false;
}
public Cursor findFirstOrLast(Session session, boolean first) {
throw DbException.getUnsupportedException("SCAN");
}
Iterator getDelta() {
if (delta == null) {
List e = Collections.emptyList();
return e.iterator();
}
return delta.iterator();
}
public long getRowCountApproximation() {
return rowCount;
}
public String getPlanSQL() {
return table.getSQL() + ".tableScan";
}
}
