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*
* http://www.apache.org/licenses/LICENSE-2.0
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*/
package org.apache.cassandra.db;
import java.nio.ByteBuffer;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import org.apache.cassandra.db.rows.Row;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.serializers.MarshalException;
import org.apache.cassandra.io.sstable.IndexInfo;
/**
* A comparator of clustering prefixes (or more generally of {@link Clusterable}}.
*
* This is essentially just a composite comparator that the clustering values of the provided
* clustering prefixes in lexicographical order, with each component being compared based on
* the type of the clustering column this is a value of.
*/
public class ClusteringComparator implements Comparator
{
private final List> clusteringTypes;
private final Comparator indexComparator;
private final Comparator indexReverseComparator;
private final Comparator reverseComparator;
private final Comparator rowComparator = (r1, r2) -> compare(r1.clustering(), r2.clustering());
public ClusteringComparator(AbstractType... clusteringTypes)
{
this(ImmutableList.copyOf(clusteringTypes));
}
public ClusteringComparator(List> clusteringTypes)
{
// copy the list to ensure despatch is monomorphic
this.clusteringTypes = ImmutableList.copyOf(clusteringTypes);
this.indexComparator = (o1, o2) -> ClusteringComparator.this.compare(o1.lastName, o2.lastName);
this.indexReverseComparator = (o1, o2) -> ClusteringComparator.this.compare(o1.firstName, o2.firstName);
this.reverseComparator = (c1, c2) -> ClusteringComparator.this.compare(c2, c1);
for (AbstractType type : clusteringTypes)
type.checkComparable(); // this should already be enforced by CFMetaData.rebuild, but we check again for other constructors
}
/**
* The number of clustering columns for the table this is the comparator of.
*/
public int size()
{
return clusteringTypes.size();
}
/**
* The "subtypes" of this clustering comparator, that is the types of the clustering
* columns for the table this is a comparator of.
*/
public List> subtypes()
{
return clusteringTypes;
}
/**
* Returns the type of the ith clustering column of the table.
*/
public AbstractType subtype(int i)
{
return clusteringTypes.get(i);
}
/**
* Creates a row clustering based on the clustering values.
*
* Every argument can either be a {@code ByteBuffer}, in which case it is used as-is, or a object
* corresponding to the type of the corresponding clustering column, in which case it will be
* converted to a byte buffer using the column type.
*
* @param values the values to use for the created clustering. There should be exactly {@code size()}
* values which must be either byte buffers or of the type the column expect.
*
* @return the newly created clustering.
*/
public Clustering make(Object... values)
{
if (values.length != size())
throw new IllegalArgumentException(String.format("Invalid number of components, expecting %d but got %d", size(), values.length));
CBuilder builder = CBuilder.create(this);
for (Object val : values)
{
if (val instanceof ByteBuffer)
builder.add((ByteBuffer) val);
else
builder.add(val);
}
return builder.build();
}
public int compare(Clusterable c1, Clusterable c2)
{
return compare(c1.clustering(), c2.clustering());
}
public int compare(ClusteringPrefix c1, ClusteringPrefix c2)
{
int s1 = c1.size();
int s2 = c2.size();
int minSize = Math.min(s1, s2);
for (int i = 0; i < minSize; i++)
{
int cmp = compareComponent(i, c1.get(i), c2.get(i));
if (cmp != 0)
return cmp;
}
if (s1 == s2)
return ClusteringPrefix.Kind.compare(c1.kind(), c2.kind());
return s1 < s2 ? c1.kind().comparedToClustering : -c2.kind().comparedToClustering;
}
public int compare(Clustering c1, Clustering c2)
{
return compare(c1, c2, size());
}
/**
* Compares the specified part of the specified clusterings.
*
* @param c1 the first clustering
* @param c2 the second clustering
* @param size the number of components to compare
* @return a negative integer, zero, or a positive integer as the first argument is less than,
* equal to, or greater than the second.
*/
public int compare(Clustering c1, Clustering c2, int size)
{
for (int i = 0; i < size; i++)
{
int cmp = compareComponent(i, c1.get(i), c2.get(i));
if (cmp != 0)
return cmp;
}
return 0;
}
public int compareComponent(int i, ByteBuffer v1, ByteBuffer v2)
{
if (v1 == null)
return v2 == null ? 0 : -1;
if (v2 == null)
return 1;
return clusteringTypes.get(i).compare(v1, v2);
}
/**
* Returns whether this clustering comparator is compatible with the provided one,
* that is if the provided one can be safely replaced by this new one.
*
* @param previous the previous comparator that we want to replace and test
* compatibility with.
*
* @return whether {@code previous} can be safely replaced by this comparator.
*/
public boolean isCompatibleWith(ClusteringComparator previous)
{
if (this == previous)
return true;
// Extending with new components is fine, shrinking is not
if (size() < previous.size())
return false;
for (int i = 0; i < previous.size(); i++)
{
AbstractType tprev = previous.subtype(i);
AbstractType tnew = subtype(i);
if (!tnew.isCompatibleWith(tprev))
return false;
}
return true;
}
/**
* Validates the provided prefix for corrupted data.
*
* @param clustering the clustering prefix to validate.
*
* @throws MarshalException if {@code clustering} contains some invalid data.
*/
public void validate(ClusteringPrefix clustering)
{
for (int i = 0; i < clustering.size(); i++)
{
ByteBuffer value = clustering.get(i);
if (value != null)
subtype(i).validate(value);
}
}
/**
* A comparator for rows.
*
* A {@code Row} is a {@code Clusterable} so {@code ClusteringComparator} can be used
* to compare rows directly, but when we know we deal with rows (and not {@code Clusterable} in
* general), this is a little faster because by knowing we compare {@code Clustering} objects,
* we know that 1) they all have the same size and 2) they all have the same kind.
*/
public Comparator rowComparator()
{
return rowComparator;
}
public Comparator indexComparator(boolean reversed)
{
return reversed ? indexReverseComparator : indexComparator;
}
public Comparator reversed()
{
return reverseComparator;
}
@Override
public String toString()
{
return String.format("comparator(%s)", Joiner.on(", ").join(clusteringTypes));
}
@Override
public boolean equals(Object o)
{
if (this == o)
return true;
if (!(o instanceof ClusteringComparator))
return false;
ClusteringComparator that = (ClusteringComparator)o;
return this.clusteringTypes.equals(that.clusteringTypes);
}
@Override
public int hashCode()
{
return Objects.hashCode(clusteringTypes);
}
}