hashindex.java

非常棒的java数据库

/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.index;

import java.sql.SQLException;

import org.h2.engine.Session;
import org.h2.message.Message;
import org.h2.result.Row;
import org.h2.result.SearchRow;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.TableData;
import org.h2.util.IntIntHashMap;
import org.h2.util.ObjectUtils;
import org.h2.util.ValueHashMap;
import org.h2.value.Value;
import org.h2.value.ValueArray;

/**
 * An index based on an in-memory hash map.
 */
public class HashIndex extends BaseIndex {

    private ValueHashMap rows;
    private IntIntHashMap intMap;
    private TableData tableData;

    public HashIndex(TableData table, int id, String indexName, IndexColumn[] columns, IndexType indexType) {
        super(table, id, indexName, columns, indexType);
        this.tableData = table;
        reset();
    }

    private void reset() {
        if (columns.length == 1 && columns[0].getType() == Value.INT) {
            intMap = new IntIntHashMap();
        } else {
            rows = new ValueHashMap(table.getDatabase());
        }
    }

    public void close(Session session) {
        // nothing to do
    }

    public void truncate(Session session) throws SQLException {
        reset();
    }

    public void remove(Session session) throws SQLException {
        // nothing to do
    }

    public void add(Session session, Row row) throws SQLException {
        if (intMap != null) {
            int key = row.getValue(columns[0].getColumnId()).getInt();
            intMap.put(key, row.getPos());
        } else {
            Value key = getKey(row);
            Object old = rows.get(key);
            if (old != null) {
                // TODO index duplicate key for hash indexes: is this allowed?
                throw getDuplicateKeyException();
            }
            Integer pos = ObjectUtils.getInteger(row.getPos());
            rows.put(getKey(row), pos);
        }
        rowCount++;
    }

    public void remove(Session session, Row row) throws SQLException {
        if (intMap != null) {
            int key = row.getValue(columns[0].getColumnId()).getInt();
            intMap.remove(key);
        } else {
            rows.remove(getKey(row));
        }
        rowCount--;
    }

    private Value getKey(SearchRow row) {
        if (columns.length == 1) {
            Column column = columns[0];
            int index = column.getColumnId();
            Value v = row.getValue(index);
            return v;
        }
        Value[] list = new Value[columns.length];
        for (int i = 0; i < columns.length; i++) {
            Column column = columns[i];
            int index = column.getColumnId();
            list[i] = row.getValue(index);
        }
        return ValueArray.get(list);
    }

    public Cursor find(Session session, SearchRow first, SearchRow last) throws SQLException {
        if (first == null || last == null) {
            // TODO hash index: should additionally check if values are the same
            throw Message.getInternalError();
        }
        Row result;
        if (intMap != null) {
            int key = first.getValue(columns[0].getColumnId()).getInt();
            int pos = intMap.get(key);
            if (pos != IntIntHashMap.NOT_FOUND) {
                result = tableData.getRow(session, pos);
            } else {
                result = null;
            }
        } else {
            Integer pos = (Integer) rows.get(getKey(first));
            if (pos == null) {
                result = null;
            } else {
                result = tableData.getRow(session, pos.intValue());
            }
        }
        return new HashCursor(result);
    }

    public double getCost(Session session, int[] masks) {
        for (int i = 0; i < columns.length; i++) {
            Column column = columns[i];
            int index = column.getColumnId();
            int mask = masks[index];
            if ((mask & IndexCondition.EQUALITY) != IndexCondition.EQUALITY) {
                return Long.MAX_VALUE;
            }
        }
        return 2;
    }

    public void checkRename() throws SQLException {
        // ok
    }

    public boolean needRebuild() {
        return true;
    }

    public boolean canGetFirstOrLast() {
        return false;
    }

    public SearchRow findFirstOrLast(Session session, boolean first) throws SQLException {
        throw Message.getUnsupportedException();
    }

}