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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.selection;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.List;
import org.apache.cassandra.cql3.ColumnIdentifier;
import org.apache.cassandra.cql3.ColumnSpecification;
import org.apache.cassandra.cql3.QueryOptions;
import org.apache.cassandra.cql3.functions.Function;
import org.apache.cassandra.cql3.selection.ColumnTimestamps.TimestampsType;
import org.apache.cassandra.db.TypeSizes;
import org.apache.cassandra.db.context.CounterContext;
import org.apache.cassandra.db.filter.ColumnFilter;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.db.marshal.CollectionType;
import org.apache.cassandra.db.marshal.UserType;
import org.apache.cassandra.db.rows.Cell;
import org.apache.cassandra.db.rows.ColumnData;
import org.apache.cassandra.db.rows.ComplexColumnData;
import org.apache.cassandra.exceptions.InvalidRequestException;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.schema.CQLTypeParser;
import org.apache.cassandra.schema.ColumnMetadata;
import org.apache.cassandra.schema.KeyspaceMetadata;
import org.apache.cassandra.schema.Schema;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.transport.ProtocolVersion;
import org.apache.cassandra.utils.ByteBufferUtil;
import static org.apache.cassandra.cql3.statements.RequestValidations.invalidRequest;
/**
* A Selector is used to convert the data returned by the storage engine into the data requested by the
* user. They correspond to the <selector> elements from the select clause.
* Since the introduction of aggregation, Selectors cannot be called anymore by multiple threads
* as they have an internal state.
*/
public abstract class Selector
{
protected static abstract class SelectorDeserializer
{
protected abstract Selector deserialize(DataInputPlus in, int version, TableMetadata metadata) throws IOException;
protected final AbstractType readType(TableMetadata metadata, DataInputPlus in) throws IOException
{
KeyspaceMetadata keyspace = Schema.instance.getKeyspaceMetadata(metadata.keyspace);
return readType(keyspace, in);
}
protected final AbstractType readType(KeyspaceMetadata keyspace, DataInputPlus in) throws IOException
{
String cqlType = in.readUTF();
return CQLTypeParser.parse(keyspace.name, cqlType, keyspace.types);
}
}
/**
* The Selector kinds.
*/
public enum Kind
{
SIMPLE_SELECTOR(SimpleSelector.deserializer),
TERM_SELECTOR(TermSelector.deserializer),
WRITETIME_OR_TTL_SELECTOR(WritetimeOrTTLSelector.deserializer),
LIST_SELECTOR(ListSelector.deserializer),
SET_SELECTOR(SetSelector.deserializer),
MAP_SELECTOR(MapSelector.deserializer),
TUPLE_SELECTOR(TupleSelector.deserializer),
USER_TYPE_SELECTOR(UserTypeSelector.deserializer),
FIELD_SELECTOR(FieldSelector.deserializer),
SCALAR_FUNCTION_SELECTOR(ScalarFunctionSelector.deserializer),
AGGREGATE_FUNCTION_SELECTOR(AggregateFunctionSelector.deserializer),
ELEMENT_SELECTOR(ElementsSelector.ElementSelector.deserializer),
SLICE_SELECTOR(ElementsSelector.SliceSelector.deserializer),
VECTOR_SELECTOR(VectorSelector.deserializer);
private final SelectorDeserializer deserializer;
Kind(SelectorDeserializer deserializer)
{
this.deserializer = deserializer;
}
}
/**
* A factory for Selector instances.
*/
public static abstract class Factory
{
public void addFunctionsTo(List functions)
{
}
/**
* Returns the column specification corresponding to the output value of the selector instances created by
* this factory.
*
* @param table the table meta data
* @return a column specification
*/
public ColumnSpecification getColumnSpecification(TableMetadata table)
{
return new ColumnSpecification(table.keyspace,
table.name,
new ColumnIdentifier(getColumnName(), true), // note that the name is not necessarily
// a true column name so we shouldn't intern it
getReturnType());
}
/**
* Creates a new Selector instance.
*
* @param options the options of the query for which the instance is created (some selector
* depends on the bound values in particular).
* @return a new Selector instance
*/
public abstract Selector newInstance(QueryOptions options);
/**
* Checks if this factory creates selectors instances that creates aggregates.
*
* @return true if this factory creates selectors instances that creates aggregates,
* false otherwise
*/
public boolean isAggregateSelectorFactory()
{
return false;
}
/**
* Checks if this factory creates writetime selectors instances.
*
* @return true if this factory creates writetime selectors instances,
* false otherwise
*/
public boolean isWritetimeSelectorFactory()
{
return false;
}
/**
* Checks if this factory creates maxwritetime selector instances.
*
* @return true if this factory creates maxwritetime selectors instances,
* false otherwise
*/
public boolean isMaxWritetimeSelectorFactory()
{
return false;
}
/**
* Checks if this factory creates TTL selectors instances.
*
* @return true if this factory creates TTL selectors instances,
* false otherwise
*/
public boolean isTTLSelectorFactory()
{
return false;
}
/**
* Checks if this factory creates Selectors that simply return a column value.
*
* @return true if this factory creates Selectors that simply return a column value,
* false otherwise.
*/
public boolean isSimpleSelectorFactory()
{
return false;
}
/**
* Checks if this factory creates Selectors that simply return the specified column.
*
* @param index the column index
* @return true if this factory creates Selectors that simply return
* the specified column, false otherwise.
*/
public boolean isSimpleSelectorFactoryFor(int index)
{
return false;
}
/**
* Returns the name of the column corresponding to the output value of the selector instances created by
* this factory.
*
* @return a column name
*/
protected abstract String getColumnName();
/**
* Returns the type of the values returned by the selector instances created by this factory.
*
* @return the selector output type
*/
protected abstract AbstractType getReturnType();
/**
* Record a mapping between the ColumnDefinitions that are used by the selector
* instances created by this factory and a column in the ResultSet.Metadata
* returned with a query. In most cases, this is likely to be a 1:1 mapping,
* but some selector instances may utilise multiple columns (or none at all)
* to produce a value (i.e. functions).
*
* @param mapping the instance of the column mapping belonging to the current query's Selection
* @param resultsColumn the column in the ResultSet.Metadata to which the ColumnDefinitions used
* by the Selector are to be mapped
*/
protected abstract void addColumnMapping(SelectionColumnMapping mapping, ColumnSpecification resultsColumn);
/**
* Checks if all the columns fetched by the selector created by this factory are known
* @return {@code true} if all the columns fetched by the selector created by this factory are known,
* {@code false} otherwise.
*/
abstract boolean areAllFetchedColumnsKnown();
/**
* Adds the columns fetched by the selector created by this factory to the provided builder, assuming the
* factory is terminal (i.e. that {@code isTerminal() == true}).
*
* @param builder the column builder to add fetched columns (and potential subselection) to.
* @throws AssertionError if the method is called on a factory where {@code isTerminal()} returns {@code false}.
*/
abstract void addFetchedColumns(ColumnFilter.Builder builder);
}
public static class Serializer
{
public void serialize(Selector selector, DataOutputPlus out, int version) throws IOException
{
out.writeByte(selector.kind().ordinal());
selector.serialize(out, version);
}
public Selector deserialize(DataInputPlus in, int version, TableMetadata metadata) throws IOException
{
Kind kind = Kind.values()[in.readUnsignedByte()];
return kind.deserializer.deserialize(in, version, metadata);
}
public int serializedSize(Selector selector, int version)
{
return TypeSizes.sizeof((byte) selector.kind().ordinal()) + selector.serializedSize(version);
}
}
/**
* The {@code Selector} serializer.
*/
public static final Serializer serializer = new Serializer();
/**
* The {@code Selector} kind.
*/
private final Kind kind;
/**
* Returns the {@code Selector} kind.
* @return the {@code Selector} kind
*/
public final Kind kind()
{
return kind;
}
protected Selector(Kind kind)
{
this.kind = kind;
}
/**
* Add to the provided builder the column (and potential subselections) to fetch for this
* selection.
*
* @param builder the builder to add columns and subselections to.
*/
public abstract void addFetchedColumns(ColumnFilter.Builder builder);
/**
* A row of data that need to be processed by a {@code Selector}
*/
public static final class InputRow
{
private final ProtocolVersion protocolVersion;
private final List columns;
private final boolean unmask;
private final boolean collectWritetimes;
private final boolean collectTTLs;
private ByteBuffer[] values;
private RowTimestamps writetimes;
private RowTimestamps ttls;
private int index;
public InputRow(ProtocolVersion protocolVersion, List columns, boolean unmask)
{
this(protocolVersion, columns, unmask, false, false);
}
public InputRow(ProtocolVersion protocolVersion,
List columns,
boolean unmask,
boolean collectWritetimes,
boolean collectTTLs)
{
this.protocolVersion = protocolVersion;
this.columns = columns;
this.unmask = unmask;
this.collectWritetimes = collectWritetimes;
this.collectTTLs = collectTTLs;
values = new ByteBuffer[columns.size()];
writetimes = initTimestamps(TimestampsType.WRITETIMES, collectWritetimes, columns);
ttls = initTimestamps(TimestampsType.TTLS, collectTTLs, columns);
}
private RowTimestamps initTimestamps(TimestampsType type,
boolean collectWritetimes,
List columns)
{
return collectWritetimes ? RowTimestamps.newInstance(type, columns)
: RowTimestamps.NOOP_ROW_TIMESTAMPS;
}
public ProtocolVersion getProtocolVersion()
{
return protocolVersion;
}
public boolean unmask()
{
return unmask;
}
public void add(ByteBuffer v)
{
values[index] = v;
if (v != null)
{
writetimes.addNoTimestamp(index);
ttls.addNoTimestamp(index);
}
index++;
}
public void add(ColumnData columnData, long nowInSec)
{
ColumnMetadata column = columns.get(index);
if (columnData == null)
{
add(null);
}
else
{
if (column.isComplex())
{
add((ComplexColumnData) columnData, nowInSec);
}
else
{
add((Cell) columnData, nowInSec);
}
}
}
private void add(Cell c, long nowInSec)
{
values[index] = value(c);
writetimes.addTimestamp(index, c, nowInSec);
ttls.addTimestamp(index, c, nowInSec);
index++;
}
private void add(ComplexColumnData ccd, long nowInSec)
{
AbstractType type = columns.get(index).type;
if (type.isCollection())
{
values[index] = ((CollectionType) type).serializeForNativeProtocol(ccd.iterator());
for (Cell cell : ccd)
{
writetimes.addTimestamp(index, cell, nowInSec);
ttls.addTimestamp(index, cell, nowInSec);
}
}
else
{
UserType udt = (UserType) type;
int size = udt.size();
values[index] = udt.serializeForNativeProtocol(ccd.iterator(), protocolVersion);
short fieldPosition = 0;
for (Cell cell : ccd)
{
// handle null fields that aren't at the end
short fieldPositionOfCell = ByteBufferUtil.toShort(cell.path().get(0));
while (fieldPosition < fieldPositionOfCell)
{
fieldPosition++;
writetimes.addNoTimestamp(index);
ttls.addNoTimestamp(index);
}
fieldPosition++;
writetimes.addTimestamp(index, cell, nowInSec);
ttls.addTimestamp(index, cell, nowInSec);
}
// append nulls for missing cells
while (fieldPosition < size)
{
fieldPosition++;
writetimes.addNoTimestamp(index);
ttls.addNoTimestamp(index);
}
}
index++;
}
private ByteBuffer value(Cell c)
{
return c.isCounterCell()
? ByteBufferUtil.bytes(CounterContext.instance().total(c.value(), c.accessor()))
: c.buffer();
}
/**
* Return the value of the column with the specified index.
*
* @param index the column index
* @return the value of the column with the specified index
*/
public ByteBuffer getValue(int index)
{
return values[index];
}
/**
* Reset the row internal state.
* If the reset is not a deep one only the index will be reset. If the reset is a deep one a new
* array will be created to store the column values. This allow to reduce object creation when it is not
* necessary.
*
* @param deep {@code true} if the reset must be a deep one.
*/
public void reset(boolean deep)
{
index = 0;
this.writetimes = initTimestamps(TimestampsType.WRITETIMES, collectWritetimes, columns);
this.ttls = initTimestamps(TimestampsType.TTLS, collectTTLs, columns);
if (deep)
values = new ByteBuffer[values.length];
}
/**
* Return the timestamp of the column component with the specified indexes.
*
* @return the timestamp of the cell with the specified indexes
*/
ColumnTimestamps getWritetimes(int columnIndex)
{
return writetimes.get(columnIndex);
}
/**
* Return the ttl of the column component with the specified column and cell indexes.
*
* @param columnIndex the column index
* @return the ttl of the column with the specified indexes
*/
ColumnTimestamps getTtls(int columnIndex)
{
return ttls.get(columnIndex);
}
/**
* Returns the column values as list.
* This content of the list will be shared with the {@code InputRow} unless a deep reset has been done.
*
* @return the column values as list.
*/
public List getValues()
{
return Arrays.asList(values);
}
}
/**
* Add the current value from the specified ResultSetBuilder.
*
* @param input the input row
* @throws InvalidRequestException if a problem occurs while adding the input row
*/
public abstract void addInput(InputRow input);
/**
* Returns the selector output.
*
* @param protocolVersion protocol version used for serialization
* @return the selector output
* @throws InvalidRequestException if a problem occurs while computing the output value
*/
public abstract ByteBuffer getOutput(ProtocolVersion protocolVersion) throws InvalidRequestException;
protected ColumnTimestamps getWritetimes(ProtocolVersion protocolVersion)
{
throw new UnsupportedOperationException();
}
protected ColumnTimestamps getTTLs(ProtocolVersion protocolVersion)
{
throw new UnsupportedOperationException();
}
/**
* Returns the Selector output type.
*
* @return the Selector output type.
*/
public abstract AbstractType getType();
/**
* Reset the internal state of this Selector.
*/
public abstract void reset();
/**
* A selector is terminal if it doesn't require any input for it's output to be computed, i.e. if {@link #getOutput}
* result doesn't depend of {@link #addInput}. This is typically the case of a constant value or functions on constant
* values.
*/
public boolean isTerminal()
{
return false;
}
/**
* Checks that this selector is valid for GROUP BY clause.
*/
public void validateForGroupBy()
{
throw invalidRequest("Only column names and monotonic scalar functions are supported in the GROUP BY clause.");
}
protected abstract int serializedSize(int version);
protected abstract void serialize(DataOutputPlus out, int version) throws IOException;
protected static void writeType(DataOutputPlus out, AbstractType type) throws IOException
{
out.writeUTF(type.asCQL3Type().toString());
}
protected static int sizeOf(AbstractType type)
{
return TypeSizes.sizeof(type.asCQL3Type().toString());
}
}