Examples of com.sleepycat.je.DiskOrderedCursor

com.sleepycat.je.DiskOrderedCursor
DiskOrderedCursor returns records in unsorted order in exchange for generally faster retrieval times. Instead of key order, an approximation of disk order is used, which results in less I/O. This can be useful when the application needs to scan all records in a database, and will be applying filtering logic which does not need key ordered retrieval. DiskOrderedCursor is created using the {@link Database#openCursor(DiskOrderedCursorConfig)} method.
All cursors can consume resources and should be closed as soon as the application is finished using them. In particular, a DiskOrderedCursor disables the file deletion done by log cleaning, and will therefore delay the compaction of log files.
Optional configurations: the following options are available to tune the DiskOrderedCursor.
The DiskOrderedCursor creates a background producer thread which prefetches some target records and inserts them in a queue for use by the cursor. The parameter {@link EnvironmentConfig#DOS_PRODUCER_QUEUE_TIMEOUT} applies tothis background thread, and controls the timeout which governs the blocking queue.
When the DiskOrderedCursor is first created, it is "seeded" with in-memory internal B-Tree nodes. This seeding causes the root and all seed INs to be latched for read, for use by the cursor. Seeded B-Tree nodes help the efficiency of the cursor, but penalize any concurrent update operations which require write locks on those nodes. {@link DiskOrderedCursorConfig#setMaxSeedMillisecs} can be used tolimit the time spent on the seeding process in exchange for reduced performance during the cursor walk.
{@link DiskOrderedCursorConfig#setMaxSeedNodes} can be used tolimit the number of nodes used to seed the DiskOrderedCursor, which also can reduce cursor performance, but improves the performance of concurrent write operations. @since 5.0

        final boolean trace = LOG.isTraceEnabled();


        final DatabaseEntry key = new DatabaseEntry();
        final DatabaseEntry data = new DatabaseEntry();


        final DiskOrderedCursor cursor = ownerDirectory.openCursor(new DiskOrderedCursorConfig().setKeysOnly(true));


        try {
            OperationStatus retVal = cursor.getNext(key, data, null);
            while (retVal == OperationStatus.SUCCESS) {
                if (trace)
                    LOG.trace("Owner of {} -> 0", Longs.fromByteArray(key.getData()));


                ownerDirectory.put(null, key, SERVER);
                retVal = cursor.getNext(key, data, null);
            }
        } finally {
            cursor.close();
        }
    }

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        final boolean trace = LOG.isTraceEnabled();


        final DatabaseEntry key = new DatabaseEntry();
        final DatabaseEntry data = new DatabaseEntry();


        final DiskOrderedCursor cursor = ownerDirectory.openCursor(new DiskOrderedCursorConfig().setKeysOnly(true));


        try {
            OperationStatus retVal = cursor.getNext(key, data, null);
            while (retVal == OperationStatus.SUCCESS) {
                if (trace)
                    LOG.trace("Owner of {} -> 0", Longs.fromByteArray(key.getData()));


                ownerDirectory.put(null, key, SERVER);
                retVal = cursor.getNext(key, data, null);
            }
        } finally {
            cursor.close();
        }
    }

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        final boolean trace = LOG.isTraceEnabled();


        final DatabaseEntry key = new DatabaseEntry();
        final DatabaseEntry data = new DatabaseEntry();


        final DiskOrderedCursor cursor = ownerDirectory.openCursor(new DiskOrderedCursorConfig().setKeysOnly(true));


        try {
            OperationStatus retVal = cursor.getNext(key, data, null);
            while (retVal == OperationStatus.SUCCESS) {
                if (trace)
                    LOG.trace("Owner of {} -> 0", Longs.fromByteArray(key.getData()));


                ownerDirectory.put(null, key, SERVER);
                retVal = cursor.getNext(key, data, null);
            }
        } finally {
            cursor.close();
        }
    }

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