org.apache.cassandra.cql.common.ColumnRangeQueryRSD.java Source code

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Here is the source code for org.apache.cassandra.cql.common.ColumnRangeQueryRSD.java

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/**
 * 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.cassandra.cql.common;

import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.List;
import java.io.UnsupportedEncodingException;

import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.cql.execution.RuntimeErrorMsg;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.filter.QueryPath;
import org.apache.cassandra.service.ConsistencyLevel;
import org.apache.cassandra.service.StorageProxy;
import org.apache.cassandra.service.StorageService;
import org.apache.cassandra.utils.LogUtil;
import org.apache.log4j.Logger;
import org.apache.commons.lang.ArrayUtils;

/**
 * A Row Source Defintion (RSD) for doing a range query on a column map
 * (in Standard or Super Column Family).
 */
public class ColumnRangeQueryRSD extends RowSourceDef {
    private final static Logger logger_ = Logger.getLogger(ColumnRangeQueryRSD.class);
    private CFMetaData cfMetaData_;
    private OperandDef rowKey_;
    private OperandDef superColumnKey_;
    private int limit_;

    /**
     * Set up a range query on column map in a simple column family.
     * The column map in a simple column family is identified by the rowKey.
     * 
     * Note: "limit" of -1 is the equivalent of no limit.
     *       "offset" specifies the number of rows to skip. An offset of 0 implies from the first row.
     */
    public ColumnRangeQueryRSD(CFMetaData cfMetaData, OperandDef rowKey, int limit) {
        cfMetaData_ = cfMetaData;
        rowKey_ = rowKey;
        superColumnKey_ = null;
        limit_ = limit;
    }

    /**
     * Setup a range query on a column map in a super column family.
     * The column map in a super column family is identified by the rowKey & superColumnKey.
     *  
     * Note: "limit" of -1 is the equivalent of no limit.
     *       "offset" specifies the number of rows to skip. An offset of 0 implies the first row.  
     */
    public ColumnRangeQueryRSD(CFMetaData cfMetaData, ConstantOperand rowKey, ConstantOperand superColumnKey,
            int limit) {
        cfMetaData_ = cfMetaData;
        rowKey_ = rowKey;
        superColumnKey_ = superColumnKey;
        limit_ = limit;
    }

    public List<Map<String, String>> getRows() throws UnsupportedEncodingException {
        QueryPath path;
        String superColumnKey = null;

        if (superColumnKey_ != null) {
            superColumnKey = (String) (superColumnKey_.get());
            path = new QueryPath(cfMetaData_.cfName, superColumnKey.getBytes("UTF-8"));
        } else {
            path = new QueryPath(cfMetaData_.cfName);
        }

        Row row = null;
        try {
            String key = (String) (rowKey_.get());
            ReadCommand readCommand = new SliceFromReadCommand(cfMetaData_.tableName, key, path,
                    ArrayUtils.EMPTY_BYTE_ARRAY, ArrayUtils.EMPTY_BYTE_ARRAY, true, limit_);
            row = StorageProxy.readProtocol(readCommand, ConsistencyLevel.ONE);
        } catch (Exception e) {
            logger_.error(LogUtil.throwableToString(e));
            throw new RuntimeException(RuntimeErrorMsg.GENERIC_ERROR.getMsg());
        }

        List<Map<String, String>> rows = new LinkedList<Map<String, String>>();
        if (row != null) {
            ColumnFamily cfamily = row.getColumnFamily(cfMetaData_.cfName);
            if (cfamily != null) {
                Collection<IColumn> columns = null;
                if (superColumnKey_ != null) {
                    // this is the super column case
                    IColumn column = cfamily.getColumn(superColumnKey.getBytes("UTF-8"));
                    if (column != null)
                        columns = column.getSubColumns();
                } else {
                    columns = cfamily.getSortedColumns();
                }

                if (columns != null && columns.size() > 0) {
                    for (IColumn column : columns) {
                        Map<String, String> result = new HashMap<String, String>();

                        result.put(cfMetaData_.n_columnKey, new String(column.name(), "UTF-8"));
                        result.put(cfMetaData_.n_columnValue, new String(column.value()));
                        result.put(cfMetaData_.n_columnTimestamp, Long.toString(column.timestamp()));

                        rows.add(result);
                    }
                }
            }
        }
        return rows;
    }

    public String explainPlan() {
        return String.format(
                "%s Column Family: Column Range Query: \n" + "  Table Name:       %s\n" + "  Column Family:    %s\n"
                        + "  RowKey:           %s\n" + "%s" + "  Limit:            %d\n" + "  Order By:         %s",
                cfMetaData_.columnType, cfMetaData_.tableName, cfMetaData_.cfName, rowKey_.explain(),
                (superColumnKey_ == null) ? "" : "  SuperColumnKey:   " + superColumnKey_.explain() + "\n", limit_,
                cfMetaData_.comparator);
    }
}