phoenix-core/src/main/java/org/apache/phoenix/parse/DistinctCountParseNode.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.phoenix.parse;

import java.sql.SQLException;
import java.util.List;

import org.apache.phoenix.compile.ColumnResolver;
import org.apache.phoenix.compile.StatementContext;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.function.DistinctCountAggregateFunction;
import org.apache.phoenix.expression.function.FunctionExpression;

/**
 * 
 * 
 * @since 1.2.1
 */
public class DistinctCountParseNode extends DelegateConstantToCountParseNode {
    
    public DistinctCountParseNode(String name, List<ParseNode> children, BuiltInFunctionInfo info) {
        super(name, children, info);
    }

    @Override
    public FunctionExpression create(List<Expression> children, StatementContext context)
            throws SQLException {
        return new DistinctCountAggregateFunction(children, getDelegateFunction(children, context));
    }
    
    @Override
    public void toSQL(ColumnResolver resolver, StringBuilder buf) {
        buf.append(' ');
        buf.append("COUNT(DISTINCT ");
        List<ParseNode> children = getChildren();
        if (!children.isEmpty()) {
            for (ParseNode child : children) {
                child.toSQL(resolver, buf);
                buf.append(',');
            }
            buf.setLength(buf.length()-1);
        }
        buf.append(')');
    }
}