/**
* 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.drill.exec.vector;
import java.io.Closeable;
import io.netty.buffer.DrillBuf;
import org.apache.drill.exec.exception.OutOfMemoryException;
import org.apache.drill.exec.memory.BufferAllocator;
import org.apache.drill.exec.proto.UserBitShared.SerializedField;
import org.apache.drill.exec.record.MaterializedField;
import org.apache.drill.exec.record.TransferPair;
import org.apache.drill.exec.vector.complex.reader.FieldReader;
/**
* An abstraction that is used to store a sequence of values in an individual column.
*
* A {@link ValueVector value vector} stores underlying data in-memory in a columnar fashion that is compact and
* efficient. The column whose data is stored, is referred by {@link #getField()}.
*
* A vector when instantiated, relies on a {@link org.apache.drill.exec.record.DeadBuf dead buffer}. It is important
* that vector is allocated before attempting to read or write.
*
* There are a few "rules" around vectors:
*
* <ul>
* <li>values need to be written in order (e.g. index 0, 1, 2, 5)</li>
* <li>null vectors start with all values as null before writing anything</li>
* <li>for variable width types, the offset vector should be all zeros before writing</li>
* <li>you must call setValueCount before a vector can be read</li>
* <li>you should never write to a vector once it has been read.</li>
* </ul>
*
* Please note that the current implementation doesn't enfore those rules, hence we may find few places that
* deviate from these rules (e.g. offset vectors in Variable Length and Repeated vector)
*
* This interface "should" strive to guarantee this order of operation:
* <blockquote>
* allocate > mutate > setvaluecount > access > clear (or allocate to start the process over).
* </blockquote>
*/
public interface ValueVector extends Closeable, Iterable<ValueVector> {
/**
* Allocate new buffers. ValueVector implements logic to determine how much to allocate.
* @throws OutOfMemoryException Thrown if no memory can be allocated.
*/
void allocateNew() throws OutOfMemoryException;
/**
* Allocates new buffers. ValueVector implements logic to determine how much to allocate.
* @return Returns true if allocation was succesful.
*/
boolean allocateNewSafe();
BufferAllocator getAllocator();
/**
* Set the initial record capacity
* @param numRecords
*/
void setInitialCapacity(int numRecords);
/**
* Returns the maximum number of values that can be stored in this vector instance.
*/
int getValueCapacity();
/**
* Alternative to clear(). Allows use as an AutoCloseable in try-with-resources.
*/
@Override
void close();
/**
* Release the underlying DrillBuf and reset the ValueVector to empty.
*/
void clear();
/**
* Get information about how this field is materialized.
*/
MaterializedField getField();
/**
* Returns a {@link org.apache.drill.exec.record.TransferPair transfer pair}, creating a new target vector of
* the same type.
*/
TransferPair getTransferPair(BufferAllocator allocator);
TransferPair getTransferPair(String ref, BufferAllocator allocator);
/**
* Returns a new {@link org.apache.drill.exec.record.TransferPair transfer pair} that is used to transfer underlying
* buffers into the target vector.
*/
TransferPair makeTransferPair(ValueVector target);
/**
* Returns an {@link org.apache.drill.exec.vector.ValueVector.Accessor accessor} that is used to read from this vector
* instance.
*/
Accessor getAccessor();
/**
* Returns an {@link org.apache.drill.exec.vector.ValueVector.Mutator mutator} that is used to write to this vector
* instance.
*/
Mutator getMutator();
/**
* Returns a {@link org.apache.drill.exec.vector.complex.reader.FieldReader field reader} that supports reading values
* from this vector.
*/
FieldReader getReader();
/**
* Get the metadata for this field. Used in serialization
*
* @return FieldMetadata for this field.
*/
SerializedField getMetadata();
/**
* Returns the number of bytes that is used by this vector instance.
*/
int getBufferSize();
/**
* Returns the number of bytes that is used by this vector if it holds the given number
* of values. The result will be the same as if Mutator.setValueCount() were called, followed
* by calling getBufferSize(), but without any of the closing side-effects that setValueCount()
* implies wrt finishing off the population of a vector. Some operations might wish to use
* this to determine how much memory has been used by a vector so far, even though it is
* not finished being populated.
*
* @param valueCount the number of values to assume this vector contains
* @return the buffer size if this vector is holding valueCount values
*/
int getBufferSizeFor(int valueCount);
/**
* Return the underlying buffers associated with this vector. Note that this doesn't impact the reference counts for
* this buffer so it only should be used for in-context access. Also note that this buffer changes regularly thus
* external classes shouldn't hold a reference to it (unless they change it).
* @param clear Whether to clear vector before returning; the buffers will still be refcounted;
* but the returned array will be the only reference to them
*
* @return The underlying {@link io.netty.buffer.DrillBuf buffers} that is used by this vector instance.
*/
DrillBuf[] getBuffers(boolean clear);
/**
* Load the data provided in the buffer. Typically used when deserializing from the wire.
*
* @param metadata
* Metadata used to decode the incoming buffer.
* @param buffer
* The buffer that contains the ValueVector.
*/
void load(SerializedField metadata, DrillBuf buffer);
/**
* Return the total memory consumed by all buffers within this vector.
*/
int getAllocatedByteCount();
/**
* Return the number of value bytes consumed by actual data.
*/
int getPayloadByteCount();
/**
* An abstraction that is used to read from this vector instance.
*/
interface Accessor {
/**
* Get the Java Object representation of the element at the specified position. Useful for testing.
*
* @param index
* Index of the value to get
*/
Object getObject(int index);
/**
* Returns the number of values that is stored in this vector.
*/
int getValueCount();
/**
* Returns true if the value at the given index is null, false otherwise.
*/
boolean isNull(int index);
}
/**
* An abstractiong that is used to write into this vector instance.
*/
interface Mutator {
/**
* Sets the number of values that is stored in this vector to the given value count.
*
* @param valueCount value count to set.
*/
void setValueCount(int valueCount);
/**
* Resets the mutator to pristine state.
*/
void reset();
/**
* @deprecated this has nothing to do with value vector abstraction and should be removed.
*/
@Deprecated
void generateTestData(int values);
}
}