| /* |
| * 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.rows; |
| |
| import java.util.Comparator; |
| |
| import org.apache.cassandra.config.ColumnDefinition; |
| import org.apache.cassandra.db.marshal.*; |
| |
| /** |
| * A {@code Comparator} use to determine which version of a {@link ColumnDefinition} should be used. |
| * <p> |
| * We can sometimes get 2 different versions of the definition of a give column due to differing types. This can happen |
| * in at least 2 cases: |
| * <ul> |
| * <li>for UDT, where new fields can be added (see CASSANDRA-13776).</li> |
| * <li>pre-CASSANDRA-12443, when we allowed type altering. And while we don't allow it anymore, it is possible |
| * to still have sstables with metadata mentioning an old pre-altering type (such old version of pre-altering |
| * types will be eventually eliminated from the system by compaction and thanks to this comparator, but we |
| * cannot guarantee when that's fully done).</li> |
| * </ul> |
| */ |
| final class ColumnDefinitionVersionComparator implements Comparator<ColumnDefinition> |
| { |
| public static final Comparator<ColumnDefinition> INSTANCE = new ColumnDefinitionVersionComparator(); |
| |
| private ColumnDefinitionVersionComparator() |
| { |
| } |
| |
| @Override |
| public int compare(ColumnDefinition v1, ColumnDefinition v2) |
| { |
| assert v1.ksName.equals(v2.ksName) |
| && v1.cfName.equals(v2.cfName) |
| && v1.name.equals(v2.name) : v1.debugString() + " != " + v2.debugString(); |
| |
| AbstractType<?> v1Type = v1.type; |
| AbstractType<?> v2Type = v2.type; |
| |
| // In most cases, this is used on equal types, and on most types, equality is cheap (most are singleton classes |
| // and just use reference equality), so evacuating that case first. |
| if (v1Type.equals(v2Type)) |
| return 0; |
| |
| // If those aren't the same type, one must be "more general" than the other, that is accept strictly more values. |
| if (v1Type.isValueCompatibleWith(v2Type)) |
| { |
| // Note: if both accept the same values, there is really no good way to prefer one over the other and so we |
| // consider them equal here. In practice, this mean we have 2 types that accepts the same values but are |
| // not equal. For internal types, TimestampType/DataType/LongType is, afaik, the only example, but as user |
| // can write custom types, who knows when this can happen. But excluding any user custom type weirdness |
| // (that would really be a bug of their type), such types should only differ in the way they sort, and as |
| // this method is only used for regular/static columns in practice, where sorting has no impact whatsoever, |
| // it shouldn't matter too much what we return here. |
| return v2Type.isValueCompatibleWith(v1Type) ? 0 : 1; |
| } |
| else if (v2Type.isValueCompatibleWith(v1Type)) |
| { |
| return -1; |
| } |
| else |
| { |
| // Neither is a super type of the other: something is pretty wrong and we probably shouldn't ignore it. |
| throw new IllegalArgumentException(String.format("Found 2 incompatible versions of column %s in %s.%s: one " + |
| "of type %s and one of type %s (but both types are incompatible)", |
| v1.name, v1.ksName, v1.cfName, v1Type, v2Type)); |
| } |
| } |
| } |