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Tue, Jul 23, 07:26

DB.java
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/**
* Copyright (c) 2010 Yahoo! Inc. All rights reserved.
*
* 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. See accompanying
* LICENSE file.
*/
package com.yahoo.ycsb;
import java.util.HashMap;
import java.util.Properties;
import java.util.Set;
import java.util.Vector;
/**
* A layer for accessing a database to be benchmarked. Each thread in the client
* will be given its own instance of whatever DB class is to be used in the test.
* This class should be constructed using a no-argument constructor, so we can
* load it dynamically. Any argument-based initialization should be
* done by init().
*
* Note that YCSB does not make any use of the return codes returned by this class.
* Instead, it keeps a count of the return values and presents them to the user.
*
* The semantics of methods such as insert, update and delete vary from database
* to database. In particular, operations may or may not be durable once these
* methods commit, and some systems may return 'success' regardless of whether
* or not a tuple with a matching key existed before the call. Rather than dictate
* the exact semantics of these methods, we recommend you either implement them
* to match the database's default semantics, or the semantics of your
* target application. For the sake of comparison between experiments we also
* recommend you explain the semantics you chose when presenting performance results.
*/
public abstract class DB
{
/**
* Properties for configuring this DB.
*/
Properties _p=new Properties();
/**
* Set the properties for this DB.
*/
public void setProperties(Properties p)
{
_p=p;
}
/**
* Get the set of properties for this DB.
*/
public Properties getProperties()
{
return _p;
}
/**
* Initialize any state for this DB.
* Called once per DB instance; there is one DB instance per client thread.
*/
public void init() throws DBException
{
}
/**
* Cleanup any state for this DB.
* Called once per DB instance; there is one DB instance per client thread.
*/
public void cleanup() throws DBException
{
}
/**
* Read a record from the database. Each field/value pair from the result will be stored in a HashMap.
*
* @param table The name of the table
* @param key The record key of the record to read.
* @param fields The list of fields to read, or null for all of them
* @param result A HashMap of field/value pairs for the result
* @return The result of the operation.
*/
public abstract Status read(String table, String key, Set<String> fields, HashMap<String,ByteIterator> result);
/**
* Perform a range scan for a set of records in the database. Each field/value pair from the result will be stored in a HashMap.
*
* @param table The name of the table
* @param startkey The record key of the first record to read.
* @param recordcount The number of records to read
* @param fields The list of fields to read, or null for all of them
* @param result A Vector of HashMaps, where each HashMap is a set field/value pairs for one record
* @return The result of the operation.
*/
public abstract Status scan(String table, String startkey, int recordcount, Set<String> fields, Vector<HashMap<String,ByteIterator>> result);
/**
* Update a record in the database. Any field/value pairs in the specified values HashMap will be written into the record with the specified
* record key, overwriting any existing values with the same field name.
*
* @param table The name of the table
* @param key The record key of the record to write.
* @param values A HashMap of field/value pairs to update in the record
* @return The result of the operation.
*/
public abstract Status update(String table, String key, HashMap<String,ByteIterator> values);
/**
* Insert a record in the database. Any field/value pairs in the specified values HashMap will be written into the record with the specified
* record key.
*
* @param table The name of the table
* @param key The record key of the record to insert.
* @param values A HashMap of field/value pairs to insert in the record
* @return The result of the operation.
*/
public abstract Status insert(String table, String key, HashMap<String,ByteIterator> values);
/**
* Delete a record from the database.
*
* @param table The name of the table
* @param key The record key of the record to delete.
* @return The result of the operation.
*/
public abstract Status delete(String table, String key);
}

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