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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.nio.ByteBuffer;
import java.util.Locale;
import java.util.concurrent.ConcurrentMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.MapMaker;
import org.apache.cassandra.cache.IMeasurableMemory;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.db.marshal.UTF8Type;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.ObjectSizes;
import org.apache.cassandra.utils.memory.AbstractAllocator;
/**
* Represents an identifer for a CQL column definition.
* TODO : should support light-weight mode without text representation for when not interned
*/
public class ColumnIdentifier implements IMeasurableMemory, Comparable
{
private static final Pattern PATTERN_DOUBLE_QUOTE = Pattern.compile("\"", Pattern.LITERAL);
private static final String ESCAPED_DOUBLE_QUOTE = Matcher.quoteReplacement("\"\"");
public final ByteBuffer bytes;
private final String text;
/**
* since these objects are compared frequently, we stash an efficiently compared prefix of the bytes, in the expectation
* that the majority of comparisons can be answered by this value only
*/
public final long prefixComparison;
private final boolean interned;
private static final Pattern UNQUOTED_IDENTIFIER = Pattern.compile("[a-z][a-z0-9_]*");
private static final long EMPTY_SIZE = ObjectSizes.measure(new ColumnIdentifier(ByteBufferUtil.EMPTY_BYTE_BUFFER, "", false));
private static final ConcurrentMap internedInstances = new MapMaker().weakValues().makeMap();
private static final class InternedKey
{
private final AbstractType type;
private final ByteBuffer bytes;
InternedKey(AbstractType type, ByteBuffer bytes)
{
this.type = type;
this.bytes = bytes;
}
@Override
public boolean equals(Object o)
{
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
InternedKey that = (InternedKey) o;
return bytes.equals(that.bytes) && type.equals(that.type);
}
@Override
public int hashCode()
{
return bytes.hashCode() + 31 * type.hashCode();
}
}
private static long prefixComparison(ByteBuffer bytes)
{
long prefix = 0;
ByteBuffer read = bytes.duplicate();
int i = 0;
while (read.hasRemaining() && i < 8)
{
prefix <<= 8;
prefix |= read.get() & 0xFF;
i++;
}
prefix <<= (8 - i) * 8;
// by flipping the top bit (==Integer.MIN_VALUE), we ensure that signed comparison gives the same result
// as an unsigned without the bit flipped
prefix ^= Long.MIN_VALUE;
return prefix;
}
public ColumnIdentifier(String rawText, boolean keepCase)
{
this.text = keepCase ? rawText : rawText.toLowerCase(Locale.US);
this.bytes = ByteBufferUtil.bytes(this.text);
this.prefixComparison = prefixComparison(bytes);
this.interned = false;
}
public ColumnIdentifier(ByteBuffer bytes, AbstractType type)
{
this(bytes, type.getString(bytes), false);
}
public ColumnIdentifier(ByteBuffer bytes, String text)
{
this(bytes, text, false);
}
private ColumnIdentifier(ByteBuffer bytes, String text, boolean interned)
{
this.bytes = bytes;
this.text = text;
this.interned = interned;
this.prefixComparison = prefixComparison(bytes);
}
public static ColumnIdentifier getInterned(ByteBuffer bytes, AbstractType type)
{
return getInterned(type, bytes, type.getString(bytes));
}
public static ColumnIdentifier getInterned(String rawText, boolean keepCase)
{
String text = keepCase ? rawText : rawText.toLowerCase(Locale.US);
ByteBuffer bytes = ByteBufferUtil.bytes(text);
return getInterned(UTF8Type.instance, bytes, text);
}
public static ColumnIdentifier getInterned(AbstractType type, ByteBuffer bytes, String text)
{
bytes = ByteBufferUtil.minimalBufferFor(bytes);
InternedKey key = new InternedKey(type, bytes);
ColumnIdentifier id = internedInstances.get(key);
if (id != null)
return id;
ColumnIdentifier created = new ColumnIdentifier(bytes, text, true);
ColumnIdentifier previous = internedInstances.putIfAbsent(key, created);
return previous == null ? created : previous;
}
public boolean isInterned()
{
return interned;
}
@Override
public final int hashCode()
{
return bytes.hashCode();
}
@Override
public final boolean equals(Object o)
{
if (this == o)
return true;
if(!(o instanceof ColumnIdentifier))
return false;
ColumnIdentifier that = (ColumnIdentifier)o;
return bytes.equals(that.bytes);
}
@Override
public String toString()
{
return text;
}
/**
* Returns a string representation of the identifier that is safe to use directly in CQL queries.
* If necessary, the string will be double-quoted, and any quotes inside the string will be escaped.
*/
public String toCQLString()
{
return maybeQuote(text);
}
public long unsharedHeapSize()
{
return EMPTY_SIZE
+ ObjectSizes.sizeOnHeapOf(bytes)
+ ObjectSizes.sizeOf(text);
}
public long unsharedHeapSizeExcludingData()
{
return EMPTY_SIZE
+ ObjectSizes.sizeOnHeapExcludingData(bytes)
+ ObjectSizes.sizeOf(text);
}
public ColumnIdentifier clone(AbstractAllocator allocator)
{
return interned ? this : new ColumnIdentifier(allocator.clone(bytes), text, false);
}
public int compareTo(ColumnIdentifier that)
{
int c = Long.compare(this.prefixComparison, that.prefixComparison);
if (c != 0)
return c;
if (this == that)
return 0;
return ByteBufferUtil.compareUnsigned(this.bytes, that.bytes);
}
@VisibleForTesting
public static String maybeQuote(String text)
{
if (UNQUOTED_IDENTIFIER.matcher(text).matches() && !ReservedKeywords.isReserved(text))
return text;
return '"' + PATTERN_DOUBLE_QUOTE.matcher(text).replaceAll(ESCAPED_DOUBLE_QUOTE) + '"';
}
}