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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.cql3;
import java.util.Collection;
public interface AssignmentTestable
{
/**
* @return whether this object can be assigned to the provided receiver. We distinguish
* between 3 values:
* - EXACT_MATCH if this object is exactly of the type expected by the receiver
* - WEAKLY_ASSIGNABLE if this object is not exactly the expected type but is assignable nonetheless
* - NOT_ASSIGNABLE if it's not assignable
* Most caller should just call the isAssignable() method on the result, though functions have a use for
* testing "strong" equality to decide the most precise overload to pick when multiple could match.
*/
public TestResult testAssignment(String keyspace, ColumnSpecification receiver);
public enum TestResult
{
EXACT_MATCH, WEAKLY_ASSIGNABLE, NOT_ASSIGNABLE;
public boolean isAssignable()
{
return this != NOT_ASSIGNABLE;
}
public boolean isExactMatch()
{
return this == EXACT_MATCH;
}
// Test all elements of toTest for assignment. If all are exact match, return exact match. If any is not assignable,
// return not assignable. Otherwise, return weakly assignable.
public static TestResult testAll(String keyspace, ColumnSpecification receiver, Collection extends AssignmentTestable> toTest)
{
TestResult res = EXACT_MATCH;
for (AssignmentTestable rt : toTest)
{
if (rt == null)
{
res = WEAKLY_ASSIGNABLE;
continue;
}
TestResult t = rt.testAssignment(keyspace, receiver);
if (t == NOT_ASSIGNABLE)
return NOT_ASSIGNABLE;
if (t == WEAKLY_ASSIGNABLE)
res = WEAKLY_ASSIGNABLE;
}
return res;
}
}
}