ConditionExists.java

/*
 * Copyright 2014-2015 the original author or authors
 *
 * Licensed under the Apache License, Version 2.0 (the “License”);
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an “AS IS” BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.wplatform.ddal.command.expression;

import com.wplatform.ddal.command.dml.Query;
import com.wplatform.ddal.dbobject.table.ColumnResolver;
import com.wplatform.ddal.dbobject.table.TableFilter;
import com.wplatform.ddal.engine.Session;
import com.wplatform.ddal.result.LocalResult;
import com.wplatform.ddal.util.StringUtils;
import com.wplatform.ddal.value.Value;
import com.wplatform.ddal.value.ValueBoolean;

/**
 * An 'exists' condition as in WHERE EXISTS(SELECT ...)
 */
public class ConditionExists extends Condition {

    private final Query query;

    public ConditionExists(Query query) {
        this.query = query;
    }

    @Override
    public Value getValue(Session session) {
        query.setSession(session);
        LocalResult result = query.query(1);
        session.addTemporaryResult(result);
        boolean r = result.getRowCount() > 0;
        return ValueBoolean.get(r);
    }

    @Override
    public Expression optimize(Session session) {
        query.prepare();
        return this;
    }

    @Override
    public String getSQL() {
        return "EXISTS(\n" + StringUtils.indent(query.getPlanSQL(), 4, false) + ")";
    }

    @Override
    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 exists (select * from test2
        // where id=count(test.id))
    }

    @Override
    public void mapColumns(ColumnResolver resolver, int level) {
        query.mapColumns(resolver, level + 1);
    }

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

    @Override
    public boolean isEverything(ExpressionVisitor visitor) {
        return query.isEverything(visitor);
    }

    @Override
    public int getCost() {
        return query.getCostAsExpression();
    }

}