Count.java example

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cobar-master
/*
 * Copyright 1999-2012 Alibaba Group.
 *  
 * 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.
 */
/**
 * (created at 2011-1-23)
 */
package com.alibaba.cobar.parser.ast.expression.primary.function.groupby;

import java.util.List;

import com.alibaba.cobar.parser.ast.expression.Expression;
import com.alibaba.cobar.parser.ast.expression.primary.function.FunctionExpression;
import com.alibaba.cobar.parser.visitor.SQLASTVisitor;

/**
 * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
 */
public class Count extends FunctionExpression {
    /**
     * either {@link distinct} or {@link wildcard} is false. if both are false,
     * expressionList must be size 1
     */
    private final boolean distinct;

    public Count(List<Expression> arguments) {
        super("COUNT", arguments);
        this.distinct = true;
    }

    public Count(Expression arg) {
        super("COUNT", wrapList(arg));
        this.distinct = false;
    }

    public boolean isDistinct() {
        return distinct;
    }

    @Override
    public FunctionExpression constructFunction(List<Expression> arguments) {
        return new Count(arguments);
    }

    @Override
    public void accept(SQLASTVisitor visitor) {
        visitor.visit(this);
    }
}