com.bigdata.rawstore.IRawStore Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Dec 19, 2006
*/
package com.bigdata.rawstore;
import java.io.File;
import java.nio.ByteBuffer;
import java.util.UUID;
import com.bigdata.btree.BTree;
import com.bigdata.counters.ICounterSetAccess;
import com.bigdata.io.IByteArrayBuffer;
import com.bigdata.journal.AbstractJournal;
import com.bigdata.mdi.IResourceMetadata;
/**
*
* A low-level interface for reading and writing data. This interface is not
* isolated and operations do not possess ACID semantics. Implementations may or
* may not be durable. All operations are expressed in terms of long integers
* that are often called "addresses" but which should be understood as opaque
* identifiers.
*
*
* The {@link AbstractJournal} is the principal implementation of this interface
* and provides both transient and durable options and the facilities for atomic
* commit. {@link BTree} provides a higher level interface for operations on an
* {@link IRawStore} and uses a copy-on-write policy designed to support
* transactional semantics by making it possible to read from a consistent
* historical state. The {@link AbstractJournal} provides the necessary
* mechanisms to support transactions based on the copy-on-write semantics of
* the {@link BTree}.
*
*
* The {@link IRawStore} supports write and read back on immutable addresses and
* does NOT directly support update of data for an immutable address once that
* data has been written. Applications seeking Create, Read, Update, Delete
* (CRUD) semantics should use a {@link BTree} to store their application data.
* Unlike this interface, the {@link BTree} can correctly support update and
* delete of application data using a persistent identifier (the key).
*
*
* @author Bryan Thompson
* @version $Id$
*
* @see AbstractJournal
* @see BTree
*
* FIXME This should be restated in terms of {@link IByteArrayBuffer}. The
* use of the {@link ByteBuffer} in this API has become limiting. It would
* be nicer to specify a byte[] with optional offset and length parameters.
* This would make it easier to wrap the byte[] in different ways for
* reading and writing. The {@link ByteBuffer} has an advantage when
* reading since it allows us to return a read-only view of the record, but
* in practice that is only effective for an in-memory store (with or
* without a backing file). The byte[] is more flexible. The caller is free
* to reuse the byte[] and the store always copies the data. In practice,
* we tend to work around this by copying to an array backed
* {@link ByteBuffer} or to a byte[] wrapped as an {@link IByteArrayBuffer}
* .
*
*/
public interface IRawStore extends IAddressManager, ICounterSetAccess, IStreamStore {
/**
* Write the data (unisolated).
*
* @param data
* The data. The bytes from the current
* {@link ByteBuffer#position()} to the
* {@link ByteBuffer#limit()} will be written and the
* {@link ByteBuffer#position()} will be advanced to the
* {@link ByteBuffer#limit()} . The caller may subsequently
* modify the contents of the buffer without changing the state
* of the store (i.e., the data are copied into the store).
*
* @return A long integer formed that encodes both the offset from which the
* data may be read and the #of bytes to be read. See
* {@link IAddressManager}.
*
* @throws IllegalArgumentException
* if data is null.
* @throws IllegalArgumentException
* if data has zero bytes {@link ByteBuffer#remaining()}.
* @throws IllegalStateException
* if the store is not open.
* @throws IllegalStateException
* if the store does not allow writes.
*
* @todo define exception if the maximum extent would be exceeded.
*
* @todo the addresses need to reflect the ascending offset at which the
* data are written, at least for a class of append only store. some
* stores, such as the Journal, also have an offset from the start of
* the file to the start of the data region (in the case of the
* Journal it is used to hold the root blocks).
*/
public long write(ByteBuffer data);
// /**
// *
// * @param data
// * The data. The bytes from the current
// * {@link ByteBuffer#position()} to the
// * {@link ByteBuffer#limit()} will be written and the
// * {@link ByteBuffer#position()} will be advanced to the
// * {@link ByteBuffer#limit()} . The caller may subsequently
// * modify the contents of the buffer without changing the state
// * of the store (i.e., the data are copied into the store).
// * @param oldAddr as returned from a previous write of the same object, or zero if a new write
// *
// * @return A long integer formed that encodes both the offset from which the
// * data may be read and the #of bytes to be read. See
// * {@link IAddressManager}.
// */
// public long write(ByteBuffer data, long oldAddr);
/**
* Delete the data (unisolated).
*
* After this operation subsequent reads on the address MAY fail and the
* caller MUST NOT depend on the ability to read at that address.
*
* @param addr
* A long integer formed using {@link Addr} that encodes both the
* offset at which the data was written and the #of bytes that
* were written.
*
* @exception IllegalArgumentException
* If the address is known to be invalid (never written or
* deleted). Note that the address 0L is always invalid.
*
* It is only applicable in the
* context of a garbage collection strategy. With an append only
* store and with eviction of btrees into index segments there
* is no reason to delete anything on the store - and nothing to
* keep track of the delete.
*
* However, with a Read-Write store it is a requirement, and a void
* implementation is provided for other stores.
*/
public void delete(long addr);
/**
* Read the data (unisolated).
*
* @param addr
* A long integer that encodes both the offset from which the
* data will be read and the #of bytes to be read. See
* {@link IAddressManager#toAddr(int, long)}.
*
* @return The data read. The buffer will be flipped to prepare for reading
* (the position will be zero and the limit will be the #of bytes
* read).
*
* @throws IllegalArgumentException
* If the address is known to be invalid (never written or
* deleted). Note that the address 0L is always invalid.
* @throws IllegalStateException
* if the store is not open.
*/
public ByteBuffer read(long addr);
/**
* true iff the store is open.
*
* @return true iff the store is open.
*/
public boolean isOpen();
/**
* true iff the store does not allow writes.
*
* @throws IllegalStateException
* if the store is not open.
*/
public boolean isReadOnly();
/**
* Close the store immediately.
*
* @exception IllegalStateException
* if the store is not open.
*/
public void close();
/**
* Deletes the backing file(s) (if any).
*
* @exception IllegalStateException
* if the store is open.
*
* @exception RuntimeException
* if the backing file exists and could not be deleted.
*/
public void deleteResources();
/**
* Closes the store immediately (if open) and deletes its persistent
* resources. Does NOT throw an {@link IllegalStateException} if the store
* is already closed, but still deletes the backing resources.
*
* @see #deleteResources()
*/
public void destroy();
/**
* The backing file -or- null if there is no backing file
* for the store.
*/
public File getFile();
/**
* Return the {@link UUID} which identifies this {@link IRawStore}. This
* supports {@link #getResourceMetadata()}.
*/
public UUID getUUID();
/**
* A description of this store in support of the scale-out architecture.
*/
public IResourceMetadata getResourceMetadata();
/**
* True iff backed by stable storage.
*
* @exception IllegalStateException
* if the store is not open.
*/
public boolean isStable();
/**
* True iff the store is fully buffered (all reads are against memory).
* Implementations MAY change the value returned by this method over the
* life cycle of the store, e.g., to conserve memory a store may drop or
* decrease its buffer if it is backed by disk.
*
* Note: This does not guarantee that the OS will not swap the buffer onto
* disk.
*
* @exception IllegalStateException
* if the store is not open.
*/
public boolean isFullyBuffered();
/**
* Force the data to stable storage. While this is NOT sufficient to
* guarantee an atomic commit, the data must be forced to disk as part of an
* atomic commit protocol.
*
* @param metadata
* If true, then force both the file contents and the file
* metadata to disk.
*
* @exception IllegalStateException
* if the store is not open.
*/
public void force(boolean metadata);
/**
* The #of application data bytes written on the store (does not count any
* headers or root blocks that may exist for the store).
*/
public long size();
// /**
// * Reports performance counters.
// */
// public CounterSet getCounters();
}