Examples of com.sleepycat.db.Cursor

com.sleepycat.db.Cursor
A database cursor. Cursors are used for operating on collections of records, for iterating over a database, and for saving handles to individual records, so that they can be modified after they have been read.
Cursors may be used by multiple threads, but only serially. That is, the application must serialize access to the handle.
If the cursor is to be used to perform operations on behalf of a transaction, the cursor must be opened and closed within the context of that single transaction.
Once the cursor close method has been called, the handle may not be accessed again, regardless of the close method's success or failure.
To obtain a cursor with default attributes:
```
 Cursor cursor = myDatabase.openCursor(txn, null); 
```
To customize the attributes of a cursor, use a CursorConfig object.
```
 CursorConfig config = new CursorConfig(); config.setDirtyRead(true); Cursor cursor = myDatabase.openCursor(txn, config); 
```
Modifications to the database during a sequential scan will be reflected in the scan; that is, records inserted behind a cursor will not be returned while records inserted in front of a cursor will be returned. In Queue and Recno databases, missing entries (that is, entries that were never explicitly created or that were created and then deleted) will be ignored during a sequential scan.

            txn = env.beginTransaction(null, null);
            autoCommit = true;
        }


        boolean failed = true;
        Cursor cursor = db.openCursor(txn, null);
        LockMode lockMode = locking ? LockMode.RMW : null;
        try {
            while (true) {
                OperationStatus status =
                    cursor.getSearchKey(keyEntry, dataEntry, lockMode);
                if (status == OperationStatus.SUCCESS) {
                    E existing =
                        (E) entityBinding.entryToObject(keyEntry, dataEntry);
                    entityBinding.objectToData(entity, dataEntry);
                    cursor.put(keyEntry, dataEntry);
                    failed = false;
                    return existing;
                } else {
                    entityBinding.objectToData(entity, dataEntry);
                    status = cursor.putNoOverwrite(keyEntry, dataEntry);
                    if (status != OperationStatus.KEYEXIST) {
                        failed = false;
                        return null;
                    }
                }
            }
        } finally {
            cursor.close();
            if (autoCommit) {
                if (failed) {
                    txn.abort();
                } else {
                    txn.commit();

View Full Code Here

    }


    private void showAllInventory()
        throws DatabaseException {
        // Get a cursor
        Cursor cursor = myDbs.getInventoryDB().openCursor(null, null);


        // DatabaseEntry objects used for reading records
        DatabaseEntry foundKey = new DatabaseEntry();
        DatabaseEntry foundData = new DatabaseEntry();


        try { // always want to make sure the cursor gets closed
            while (cursor.getNext(foundKey, foundData,
                        LockMode.DEFAULT) == OperationStatus.SUCCESS) {
                Inventory theInventory =
                    (Inventory)inventoryBinding.entryToObject(foundData);
                displayInventoryRecord(foundKey, theInventory);
            }
        } catch (Exception e) {
            System.err.println("Error on inventory cursor:");
            System.err.println(e.toString());
            e.printStackTrace();
        } finally {
            cursor.close();
        }
    }

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    // a database is to use the Database.getStats() method.
    private int countRecords(Transaction txn)  throws DatabaseException {
        DatabaseEntry key = new DatabaseEntry();
        DatabaseEntry data = new DatabaseEntry();
        int count = 0;
        Cursor cursor = null;


        try {
            // Get the cursor
            CursorConfig cc = new CursorConfig();
            // setReadUncommitted is ignored if the database was not
            // opened for uncommitted read support. TxnGuide opens
            // its database in this way, TxnGuideInMemory does not.
            cc.setReadUncommitted(true);
            cursor = myDb.openCursor(txn, cc);
            while (cursor.getNext(key, data, LockMode.DEFAULT) ==
                    OperationStatus.SUCCESS) {


                    count++;
            }
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }


        return count;

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            long count = 0;
            DatabaseEntry key = NO_RETURN_ENTRY;
            DatabaseEntry data = NO_RETURN_ENTRY;
            CursorConfig cursorConfig = locking ?
                CursorConfig.READ_UNCOMMITTED : null;
            Cursor cursor = db.openCursor(null, cursorConfig);
            try {
                OperationStatus status = cursor.getFirst(key, data, null);
                while (status == OperationStatus.SUCCESS) {
                    if (sortedDups) {
                        count += cursor.count();
                    } else {
                        count += 1;
                    }
                    status = cursor.getNextNoDup(key, data, null);
                }
            } finally {
                cursor.close();
            }
            return count;
        }
    }

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                                       KeyRange range,
                                       ValueAdapter<V> adapter,
                                       CursorConfig config)
        throws DatabaseException {


        Cursor cursor = db.openCursor(txn, config);
        RangeCursor rangeCursor =
            new RangeCursor(range, null/*pkRange*/, sortedDups, cursor);
        return new BasicCursor<V>(rangeCursor, adapter, isUpdateAllowed());
    }

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                                       KeyRange pkeyRange,
                                       ValueAdapter<V> adapter,
                                       CursorConfig config)
        throws DatabaseException {


        Cursor cursor = db.openCursor(txn, config);
        RangeCursor rangeCursor =
            new RangeCursor(singleKeyRange, pkeyRange, sortedDups, cursor);
        return new SubIndexCursor<V>(rangeCursor, adapter);
    }

View Full Code Here


        Cursor openCursor(Transaction txn, CursorConfig config)
            throws DatabaseException {


            OperationStatus status;
            Cursor cursor = db.openCursor(txn, config);
            try {
                DatabaseEntry data = BasicIndex.NO_RETURN_ENTRY;
                status = cursor.getSearchKey(key, data, null);
            } catch (DatabaseException e) {
                try {
                    cursor.close();
                } catch (DatabaseException ignored) {}
                throw e;
            }
            if (status == OperationStatus.SUCCESS) {
                return cursor;
            } else {
                cursor.close();
                return null;
            }
        }

View Full Code Here

            this.doKeys = doKeys;
            try {
                cursors = new Cursor[conditions.size()];
                for (int i = 0; i < cursors.length; i += 1) {
                    Condition cond = conditions.get(i);
                    Cursor cursor = cond.openCursor(txn, config);
                    if (cursor == null) {
                        /* Leave joinCursor null. */
                        doClose(null);
                        return;
                    }

View Full Code Here

                        firstException = e;
                    }
                }
            }
            for (int i = 0; i < cursors.length; i += 1) {
                Cursor cursor = cursors[i];
                if (cursor != null) {
                    try {
                        cursor.close();
                        cursors[i] = null;
                    } catch (DatabaseException e) {
                        if (firstException == null) {
                            firstException = e;
                        }

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     * endOperation.</p>
     */
    private Cursor beginOperation()
        throws DatabaseException {


        Cursor oldCursor = cursor;
        if (initialized) {
            cursor = dupCursor(cursor, true);
            if (secCursor != null) {
                secCursor = (SecondaryCursor) cursor;
            }

View Full Code Here

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