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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.db.lifecycle;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import org.apache.cassandra.io.sstable.SSTable;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.utils.Throwables;
import static com.google.common.base.Predicates.and;
import static com.google.common.base.Predicates.equalTo;
import static com.google.common.base.Predicates.in;
import static com.google.common.base.Predicates.not;
import static com.google.common.base.Predicates.or;
import static com.google.common.collect.Iterables.any;
import static com.google.common.collect.Iterables.concat;
import static com.google.common.collect.Iterables.filter;
import static com.google.common.collect.Iterables.getFirst;
import static org.apache.cassandra.utils.Throwables.merge;
class Helpers
{
/**
* update the contents of a set with the provided sets, ensuring that the items to remove are
* really present, and that the items to add are not (unless we're also removing them)
* @return a new set with the contents of the provided one modified
*/
static Set replace(Set original, Set remove, Iterable add)
{
return ImmutableSet.copyOf(replace(identityMap(original), remove, add).keySet());
}
/**
* update the contents of an "identity map" with the provided sets, ensuring that the items to remove are
* really present, and that the items to add are not (unless we're also removing them)
* @return a new identity map with the contents of the provided one modified
*/
static Map replace(Map original, Set remove, Iterable add)
{
// ensure the ones being removed are the exact same ones present
for (T reader : remove)
assert original.get(reader) == reader;
// ensure we don't already contain any we're adding, that we aren't also removing
assert !any(add, and(not(in(remove)), in(original.keySet()))) : String.format("original:%s remove:%s add:%s", original.keySet(), remove, add);
Map result =
identityMap(concat(add, filter(original.keySet(), not(in(remove)))));
assert result.size() == original.size() - remove.size() + Iterables.size(add) :
String.format("Expecting new size of %d, got %d while replacing %s by %s in %s",
original.size() - remove.size() + Iterables.size(add), result.size(), remove, add, original.keySet());
return result;
}
/**
* A convenience method for encapsulating this action over multiple SSTableReader with exception-safety
* @return accumulate if not null (with any thrown exception attached), or any thrown exception otherwise
*/
static void setupOnline(Iterable readers)
{
for (SSTableReader reader : readers)
reader.setupOnline();
}
/**
* A convenience method for encapsulating this action over multiple SSTableReader with exception-safety
* @return accumulate if not null (with any thrown exception attached), or any thrown exception otherwise
*/
static Throwable setReplaced(Iterable readers, Throwable accumulate)
{
for (SSTableReader reader : readers)
{
try
{
reader.setReplaced();
}
catch (Throwable t)
{
accumulate = merge(accumulate, t);
}
}
return accumulate;
}
/**
* assert that none of these readers have been replaced
*/
static void checkNotReplaced(Iterable readers)
{
for (SSTableReader reader : readers)
assert !reader.isReplaced();
}
static Throwable markObsolete(List obsoletions, Throwable accumulate)
{
if (obsoletions == null || obsoletions.isEmpty())
return accumulate;
for (LogTransaction.Obsoletion obsoletion : obsoletions)
{
try
{
obsoletion.reader.markObsolete(obsoletion.tidier);
}
catch (Throwable t)
{
accumulate = merge(accumulate, t);
}
}
return accumulate;
}
static Throwable prepareForObsoletion(Iterable readers, LogTransaction txnLogs, List obsoletions, Throwable accumulate)
{
Map logRecords = txnLogs.makeRemoveRecords(readers);
for (SSTableReader reader : readers)
{
try
{
obsoletions.add(new LogTransaction.Obsoletion(reader, txnLogs.obsoleted(reader, logRecords.get(reader))));
}
catch (Throwable t)
{
accumulate = Throwables.merge(accumulate, t);
}
}
return accumulate;
}
static Throwable abortObsoletion(List obsoletions, Throwable accumulate)
{
if (obsoletions == null || obsoletions.isEmpty())
return accumulate;
for (LogTransaction.Obsoletion obsoletion : obsoletions)
{
try
{
obsoletion.tidier.abort();
}
catch (Throwable t)
{
accumulate = merge(accumulate, t);
}
}
return accumulate;
}
/**
* @return the identity function, as a Map, with domain of the provided values
*/
static Map identityMap(Iterable values)
{
ImmutableMap.Builder builder = ImmutableMap.builder();
for (T t : values)
builder.put(t, t);
return builder.build();
}
/**
* @return an Iterable of the union if the sets, with duplicates being represented by their first encountered instance
* (as defined by the order of set provision)
*/
static Iterable concatUniq(Set... sets)
{
List> notIn = new ArrayList<>(sets.length);
for (Set set : sets)
notIn.add(not(in(set)));
List> results = new ArrayList<>(sets.length);
for (int i = 0 ; i < sets.length ; i++)
results.add(filter(sets[i], and(notIn.subList(0, i))));
return concat(results);
}
/**
* @return a Predicate yielding true for an item present in NONE of the provided sets
*/
static Predicate notIn(Set... sets)
{
return not(orIn(sets));
}
/**
* @return a Predicate yielding true for an item present in ANY of the provided sets
*/
static Predicate orIn(Collection... sets)
{
Predicate[] orIn = new Predicate[sets.length];
for (int i = 0 ; i < orIn.length ; i++)
orIn[i] = in(sets[i]);
return or(orIn);
}
/**
* filter out (i.e. remove) matching elements
* @return filter, filtered to only those elements that *are not* present in *any* of the provided sets (are present in none)
*/
static Iterable filterOut(Iterable filter, Set... inNone)
{
return filter(filter, notIn(inNone));
}
/**
* filter in (i.e. retain)
*
* @return filter, filtered to only those elements that *are* present in *any* of the provided sets
*/
static Iterable filterIn(Iterable filter, Set... inAny)
{
return filter(filter, orIn(inAny));
}
static Set emptySet()
{
return Collections.emptySet();
}
static T select(T t, Collection col)
{
if (col instanceof Set && !col.contains(t))
return null;
return getFirst(filter(col, equalTo(t)), null);
}
static T selectFirst(T t, Collection ... sets)
{
for (Collection set : sets)
{
T select = select(t, set);
if (select != null)
return select;
}
return null;
}
static Predicate idIn(Set set)
{
return idIn(identityMap(set));
}
static Predicate idIn(final Map identityMap)
{
return new Predicate()
{
public boolean apply(T t)
{
return identityMap.get(t) == t;
}
};
}
}