conditioninselect.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.expression;

import java.sql.SQLException;

import org.h2.command.dml.Query;
import org.h2.command.dml.Select;
import org.h2.constant.ErrorCode;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.message.Message;
import org.h2.result.LocalResult;
import org.h2.table.ColumnResolver;
import org.h2.table.TableFilter;
import org.h2.table.TableView;
import org.h2.value.Value;
import org.h2.value.ValueBoolean;
import org.h2.value.ValueNull;

/**
 * An 'in' condition with a subquery, as in WHERE ID IN(SELECT ...)
 */
public class ConditionInSelect extends Condition {
    private Database database;
    private Expression left;
    private Query query;
    private boolean all;
    private int compareType;
    private int queryLevel;

    public ConditionInSelect(Database database, Expression left, Query query, boolean all, int compareType) {
        this.database = database;
        this.left = left;
        this.query = query;
        this.all = all;
        this.compareType = compareType;
    }

    public Value getValue(Session session) throws SQLException {
        Value l = left.getValue(session);
        if (l == ValueNull.INSTANCE) {
            return l;
        }
        query.setSession(session);
        LocalResult rows = query.query(0);
        session.addTemporaryResult(rows);
        boolean hasNull = false;
        boolean result = all;
        while (rows.next()) {
            boolean value;
            Value r = rows.currentRow()[0];
            if (r == ValueNull.INSTANCE) {
                value = false;
                hasNull = true;
            } else {
                value = Comparison.compareNotNull(database, l, r, compareType);
            }
            if (!value && all) {
                result = false;
                break;
            } else if (value && !all) {
                result = true;
                break;
            }
        }
        if (!result && hasNull) {
            return ValueNull.INSTANCE;
        }
        return ValueBoolean.get(result);
    }

    public void mapColumns(ColumnResolver resolver, int queryLevel) throws SQLException {
        left.mapColumns(resolver, queryLevel);
        query.mapColumns(resolver, queryLevel + 1);
        this.queryLevel = Math.max(queryLevel, this.queryLevel);
    }

    public Expression optimize(Session session) throws SQLException {
        left = left.optimize(session);
        if (left == ValueExpression.NULL) {
            return left;
        }
        query.prepare();
        if (query.getColumnCount() != 1) {
            throw Message.getSQLException(ErrorCode.SUBQUERY_IS_NOT_SINGLE_COLUMN);
        }
        // Can not optimize IN(SELECT...): the data may change
        // However, could transform to an inner join
        return this;
    }

    public void setEvaluatable(TableFilter tableFilter, boolean b) {
        left.setEvaluatable(tableFilter, b);
        query.setEvaluatable(tableFilter, b);
    }

    public String getSQL() {
        StringBuffer buff = new StringBuffer("(");
        buff.append(left.getSQL());
        buff.append(" IN(");
        buff.append(query.getPlanSQL());
        buff.append("))");
        return buff.toString();
    }

    public void updateAggregate(Session session) {
        // TODO exists: is it allowed that the subquery contains aggregates?
        // probably not
        // select id from test group by id having 1 in (select * from test2
        // where id=count(test.id))
    }

    public boolean isEverything(ExpressionVisitor visitor) {
        return left.isEverything(visitor) && query.isEverything(visitor);
    }

    public int getCost() {
        return left.getCost() + 10 + (int) (10 * query.getCost());
    }

    public Expression optimizeInJoin(Session session, Select select) throws SQLException {
        if (all || compareType != Comparison.EQUAL) {
            return this;
        }
        if (!query.isEverything(ExpressionVisitor.EVALUATABLE)) {
            return this;
        }
        String alias = query.getFirstColumnAlias(session);
        query.setDistinct(true);
        if (alias == null) {
            return this;
        }
        TableView view = TableView.createTempView(session, session.getUser(), query);
        TableFilter filter = new TableFilter(session, view, view.getName(), false, select);
        select.addTableFilter(filter, true);
        ExpressionColumn column = new ExpressionColumn(session.getDatabase(), null, view.getName(), alias);
        Comparison on = new Comparison(session, Comparison.EQUAL, left, column);
        on.mapColumns(filter, 0);
        filter.addFilterCondition(on, true);
        return ValueExpression.get(ValueBoolean.get(true));
    }

}