/*
* 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.service.pager;
import java.nio.ByteBuffer;
import java.util.Iterator;
import java.util.List;
import org.apache.cassandra.config.Schema;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.filter.ColumnCounter;
import org.apache.cassandra.db.filter.NamesQueryFilter;
import org.apache.cassandra.db.filter.SliceQueryFilter;
import org.apache.cassandra.db.columniterator.IdentityQueryFilter;
import org.apache.cassandra.exceptions.RequestExecutionException;
import org.apache.cassandra.exceptions.RequestValidationException;
/**
* Static utility methods to create query pagers.
*/
public class QueryPagers
{
private QueryPagers() {};
private static int maxQueried(ReadCommand command)
{
if (command instanceof SliceByNamesReadCommand)
{
NamesQueryFilter filter = ((SliceByNamesReadCommand)command).filter;
return filter.countCQL3Rows() ? 1 : filter.columns.size();
}
else
{
SliceQueryFilter filter = ((SliceFromReadCommand)command).filter;
return filter.count;
}
}
public static boolean mayNeedPaging(Pageable command, int pageSize)
{
if (command instanceof Pageable.ReadCommands)
{
List<ReadCommand> commands = ((Pageable.ReadCommands)command).commands;
// Using long on purpose, as we could overflow otherwise
long maxQueried = 0;
for (ReadCommand readCmd : commands)
maxQueried += maxQueried(readCmd);
return maxQueried > pageSize;
}
else if (command instanceof ReadCommand)
{
return maxQueried((ReadCommand)command) > pageSize;
}
else
{
assert command instanceof RangeSliceCommand;
// We can never be sure a range slice won't need paging
return true;
}
}
private static QueryPager pager(ReadCommand command, ConsistencyLevel consistencyLevel, boolean local, PagingState state)
{
if (command instanceof SliceByNamesReadCommand)
return new NamesQueryPager((SliceByNamesReadCommand)command, consistencyLevel, local);
else
return new SliceQueryPager((SliceFromReadCommand)command, consistencyLevel, local, state);
}
private static QueryPager pager(Pageable command, ConsistencyLevel consistencyLevel, boolean local, PagingState state)
{
if (command instanceof Pageable.ReadCommands)
{
List<ReadCommand> commands = ((Pageable.ReadCommands)command).commands;
if (commands.size() == 1)
return pager(commands.get(0), consistencyLevel, local, state);
return new MultiPartitionPager(commands, consistencyLevel, local, state);
}
else if (command instanceof ReadCommand)
{
return pager((ReadCommand)command, consistencyLevel, local, state);
}
else
{
assert command instanceof RangeSliceCommand;
RangeSliceCommand rangeCommand = (RangeSliceCommand)command;
if (rangeCommand.predicate instanceof NamesQueryFilter)
return new RangeNamesQueryPager(rangeCommand, consistencyLevel, local, state);
else
return new RangeSliceQueryPager(rangeCommand, consistencyLevel, local, state);
}
}
public static QueryPager pager(Pageable command, ConsistencyLevel consistencyLevel)
{
return pager(command, consistencyLevel, false, null);
}
public static QueryPager pager(Pageable command, ConsistencyLevel consistencyLevel, PagingState state)
{
return pager(command, consistencyLevel, false, state);
}
public static QueryPager localPager(Pageable command)
{
return pager(command, null, true, null);
}
/**
* Convenience method to (locally) page an internal row.
* Used to 2ndary index a wide row without dying.
*/
public static Iterator<ColumnFamily> pageRowLocally(final ColumnFamilyStore cfs, ByteBuffer key, final int pageSize)
{
SliceFromReadCommand command = new SliceFromReadCommand(cfs.metadata.ksName, key, cfs.name, System.currentTimeMillis(), new IdentityQueryFilter());
final SliceQueryPager pager = new SliceQueryPager(command, null, true);
return new Iterator<ColumnFamily>()
{
// We don't use AbstractIterator because we don't want hasNext() to do an actual query
public boolean hasNext()
{
return !pager.isExhausted();
}
public ColumnFamily next()
{
try
{
List<Row> rows = pager.fetchPage(pageSize);
ColumnFamily cf = rows.isEmpty() ? null : rows.get(0).cf;
return cf == null ? EmptyColumns.factory.create(cfs.metadata) : cf;
}
catch (Exception e)
{
throw new RuntimeException(e);
}
}
public void remove()
{
throw new UnsupportedOperationException();
}
};
}
/**
* Convenience method that count (live) cells/rows for a given slice of a row, but page underneath.
*/
public static int countPaged(String keyspace,
String columnFamily,
ByteBuffer key,
SliceQueryFilter filter,
ConsistencyLevel consistencyLevel,
final int pageSize,
long now) throws RequestValidationException, RequestExecutionException
{
SliceFromReadCommand command = new SliceFromReadCommand(keyspace, key, columnFamily, now, filter);
final SliceQueryPager pager = new SliceQueryPager(command, consistencyLevel, false);
ColumnCounter counter = filter.columnCounter(Schema.instance.getCFMetaData(keyspace, columnFamily).comparator, now);
while (!pager.isExhausted())
{
List<Row> next = pager.fetchPage(pageSize);
if (!next.isEmpty())
counter.countAll(next.get(0).cf);
}
return counter.live();
}
}