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/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* Licensed 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 com.amazon.carbonado.repo.indexed;
import java.util.NoSuchElementException;
import org.apache.commons.logging.LogFactory;
import com.amazon.carbonado.CorruptEncodingException;
import com.amazon.carbonado.Cursor;
import com.amazon.carbonado.FetchException;
import com.amazon.carbonado.PersistException;
import com.amazon.carbonado.RepositoryException;
import com.amazon.carbonado.Storable;
import com.amazon.carbonado.Storage;
import com.amazon.carbonado.Transaction;
import com.amazon.carbonado.cursor.AbstractCursor;
import com.amazon.carbonado.cursor.FetchAheadCursor;
import com.amazon.carbonado.spi.RepairExecutor;
import com.amazon.carbonado.synthetic.SyntheticStorableReferenceAccess;
/**
* Wraps another cursor which contains index entries and extracts master
* objects from them.
*
* @author Brian S O'Neill
*/
class IndexedCursor<S extends Storable> extends AbstractCursor<S> {
private static final int FETCH_AHEAD;
static {
String prefix = IndexedCursor.class.getName() + '.';
FETCH_AHEAD = Integer.getInteger(prefix + "fetchAhead", 0);
}
private final Cursor<? extends Storable> mCursor;
private final IndexedStorage<S> mStorage;
private final SyntheticStorableReferenceAccess<S> mAccessor;
private S mNext;
IndexedCursor(Cursor<? extends Storable> indexEntryCursor,
IndexedStorage<S> storage,
SyntheticStorableReferenceAccess<S> indexAccessor)
{
if (FETCH_AHEAD > 0) {
indexEntryCursor = new FetchAheadCursor(indexEntryCursor, FETCH_AHEAD);
}
mCursor = indexEntryCursor;
mStorage = storage;
mAccessor = indexAccessor;
}
public void close() throws FetchException {
mCursor.close();
}
public boolean hasNext() throws FetchException {
if (mNext != null) {
return true;
}
try {
while (mCursor.hasNext()) {
final Storable indexEntry = mCursor.next();
S master = mStorage.mMasterStorage.prepare();
mAccessor.copyToMasterPrimaryKey(indexEntry, master);
try {
if (!master.tryLoad()) {
LogFactory.getLog(getClass()).warn
("Master is missing for index entry: " + indexEntry);
continue;
}
} catch (CorruptEncodingException e) {
LogFactory.getLog(getClass()).error
("Master record for index entry is corrupt: " + indexEntry, e);
continue;
}
if (mAccessor.isConsistent(indexEntry, master)) {
mNext = master;
return true;
}
// This index entry is stale. Repair is needed.
// Insert a correct index entry, just to be sure.
try {
final IndexedRepository repo = mStorage.mRepository;
final Storage<?> indexEntryStorage =
repo.getIndexEntryStorageFor(mAccessor.getReferenceClass());
Storable newIndexEntry = indexEntryStorage.prepare();
mAccessor.copyFromMaster(newIndexEntry, master);
if (newIndexEntry.tryLoad()) {
// Good, the correct index entry exists. We'll see
// the master record eventually, so skip.
} else {
// We have no choice but to return the master, at
// the risk of seeing it multiple times. This is
// better than seeing it never.
LogFactory.getLog(getClass()).warn
("Inconsistent index entry: " + indexEntry + ", " + master);
mNext = master;
}
// Repair the stale index entry.
RepairExecutor.execute(new Runnable() {
public void run() {
Transaction txn = repo.enterTransaction();
try {
// Reload master and verify inconsistency.
S master = mStorage.mMasterStorage.prepare();
mAccessor.copyToMasterPrimaryKey(indexEntry, master);
if (master.tryLoad()) {
Storable newIndexEntry = indexEntryStorage.prepare();
mAccessor.copyFromMaster(newIndexEntry, master);
newIndexEntry.tryInsert();
indexEntry.tryDelete();
txn.commit();
}
} catch (FetchException fe) {
LogFactory.getLog(IndexedCursor.class).warn
("Unable to check if repair required for " +
"inconsistent index entry " +
indexEntry, fe);
} catch (PersistException pe) {
LogFactory.getLog(IndexedCursor.class).error
("Unable to repair inconsistent index entry " +
indexEntry, pe);
} finally {
try {
txn.exit();
} catch (PersistException pe) {
LogFactory.getLog(IndexedCursor.class).error
("Unable to repair inconsistent index entry " +
indexEntry, pe);
}
}
}
});
} catch (Exception re) {
LogFactory.getLog(getClass()).error
("Unable to inspect inconsistent index entry " +
indexEntry, re);
}
if (mNext != null) {
return true;
}
}
} catch (NoSuchElementException e) {
} catch (FetchException e) {
try {
close();
} catch (Exception e2) {
// Don't care.
}
throw e;
}
return false;
}
public S next() throws FetchException {
try {
if (hasNext()) {
S next = mNext;
mNext = null;
return next;
}
} catch (FetchException e) {
try {
close();
} catch (Exception e2) {
// Don't care.
}
throw e;
}
throw new NoSuchElementException();
}
@Override
public int skipNext(int amount) throws FetchException {
try {
if (mNext == null) {
return mCursor.skipNext(amount);
}
if (amount <= 0) {
if (amount < 0) {
throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
}
return 0;
}
mNext = null;
return 1 + mCursor.skipNext(amount - 1);
} catch (FetchException e) {
try {
close();
} catch (Exception e2) {
// Don't care.
}
throw e;
}
}
}
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