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.

            setParams(key, pKey, data);
            status = doGetPrevDup(lockMode);
            endOperation(null, status, null, null, null);
        } else if (pkRange != null && pkRange.beginKey != null) {
            status = OperationStatus.NOTFOUND;
            Cursor oldCursor = beginOperation();
            try {
                status = doGetPrevDup(lockMode);
                if (status == OperationStatus.SUCCESS &&
                    !pkRange.checkBegin(privPKey, true)) {
                    status = OperationStatus.NOTFOUND;

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            JoinCursor toClose = joinCursor;
            joinCursor = null;
            toClose.close();
        }
        if (cursor != null) {
            Cursor toClose = cursor.getCursor();
            cursor = null;
            view.currentTxn.closeCursor(toClose );
        }
        if (indexCursorsToClose != null) {
            DataCursor[] toClose = indexCursorsToClose;

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                DbCompat.setWriteCursor(cdbConfig, true);
            } else {
                cursors = cdbCursors.readCursors;
                cdbConfig = null;
            }
            Cursor cursor;
            if (cursors.size() > 0) {
                Cursor other = ((Cursor) cursors.get(0));
                cursor = other.dup(false);
            } else {
                cursor = db.openCursor(null, cdbConfig);
            }
            cursors.add(cursor);
            return cursor;

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                CdbCursors cdbCursors = (CdbCursors) cdbCursorsMap.get(db);
                if (cdbCursors != null) {
                    List cursors = writeCursor ? cdbCursors.writeCursors
                                               : cdbCursors.readCursors;
                    if (cursors.contains(cursor)) {
                        Cursor newCursor = cursor.dup(samePosition);
                        cursors.add(newCursor);
                        return newCursor;
                    }
                }
            }

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        if (dbConfig.getTransactional()) {
            txn = env.beginTransaction(null, null);
            cursorConfig = CursorConfig.READ_COMMITTED;
        }


        Cursor cursor = null;
        int nWritten = 0;
        try {
            cursor = db.openCursor(txn, cursorConfig);
            OperationStatus status = cursor.getFirst(key, data, null);
            while (status == OperationStatus.SUCCESS) {
                boolean oneWritten = false;
                if (evolveNeeded(key, data, binding)) {
                    cursor.putCurrent(data);
                    oneWritten = true;
                    nWritten += 1;
                }
                if (listener != null) {
                    EvolveInternal.updateEvent
                        (event, entityClassName, 1, oneWritten ? 1 : 0);
                    if (!listener.evolveProgress(event)) {
                        break;
                    }
                }
                if (txn != null && nWritten >= WRITES_PER_TXN) {
                    cursor.close();
                    cursor = null;
                    txn.commit();
                    txn = null;
                    txn = env.beginTransaction(null, null);
                    cursor = db.openCursor(txn, cursorConfig);
                    DatabaseEntry saveKey = KeyRange.copy(key);
                    status = cursor.getSearchKeyRange(key, data, null);
                    if (status == OperationStatus.SUCCESS &&
                        KeyRange.equalBytes(key, saveKey)) {
                        status = cursor.getNext(key, data, null);
                    }
                } else {
                    status = cursor.getNext(key, data, null);
                }
            }
        } finally {
            if (cursor != null) {
                cursor.close();
            }
            if (txn != null) {
                if (nWritten > 0) {
                    txn.commit();
                } else {

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         */
        System.out.println("\n-> Display the events between June 1 and Aug 31");
        long endDate = makeDate(Calendar.AUGUST, 31);


        /* Position the cursor and print the first event. */
        Cursor eventWindow = eventDb.openCursor(null, null);
        LongBinding.longToEntry(makeDate(Calendar.JUNE, 1), key);


        if ((eventWindow.getSearchKeyRange(key,  data, null)) !=
            OperationStatus.SUCCESS) {
            System.out.println("No events found!");
            eventWindow.close();
            return;
        }
        try {
            printEvents(key, data, eventWindow, endDate);
        } finally {
            eventWindow.close();
        }


        /*
         * Display all events, ordered by a secondary index on price.
         */

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        CursorConfig cursorConfig = null;
        if (cdbMode) {
            cursorConfig = new CursorConfig();
            DbCompat.setWriteCursor(cursorConfig, true);
        }
        Cursor cursor = null;
        Transaction txn = null;
        try {
            if (txnMode) {
                txn = db.getEnvironment().beginTransaction(null, null);
            }
            cursor = db.openCursor(txn, cursorConfig);


            /* Get the current class ID. */
            DatabaseEntry key = new DatabaseEntry(LAST_CLASS_ID_KEY);
            DatabaseEntry data = new DatabaseEntry();
            OperationStatus status = cursor.getSearchKey(key, data,
                                                         writeLockMode);
            if (status != OperationStatus.SUCCESS) {
                throw new IllegalStateException("Class ID not initialized");
            }
            byte[] idBytes = getBytes(data);


            /* Increment the ID by one and write the updated record.  */
            idBytes = incrementID(idBytes);
            data.setData(idBytes);
            cursor.put(key, data);


            /*
             * Write the new class format record whose key is the ID just
             * assigned.
             */
            byte[] keyBytes = new byte[1 + idBytes.length];
            keyBytes[0] = REC_CLASS_FORMAT;
            System.arraycopy(idBytes, 0, keyBytes, 1, idBytes.length);
            key.setData(keyBytes);


            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream oos;
            try {
                oos = new ObjectOutputStream(baos);
                oos.writeObject(classFormat);
            } catch (IOException e) {
                throw new RuntimeExceptionWrapper(e);
            }
            data.setData(baos.toByteArray());


            cursor.put(key, data);


            /*
             * Write the new class info record, using the key passed in; this
             * is done last so that a reader who gets the class info record
             * first will always find the corresponding class format record.
             */
            classInfo.setClassID(idBytes);
            classInfo.toDbt(data);


            cursor.put(classKey, data);


            /*
             * Update the maps before closing the cursor, so that the cursor
             * lock prevents other writers from duplicating this entry.
             */
            classInfo.setClassFormat(classFormat);
            classMap.put(className, classInfo);
            formatMap.put(new BigInteger(idBytes), classFormat);
            return classInfo;
        } finally {
            if (cursor != null) {
                cursor.close();
            }
            if (txn != null) {
                txn.commit();
            }
        }

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      TestUtils.DEBUGOUT("Put: " + (char)outbuf[0] + ": " + new String(outbuf, 0, i));
      db.putNoOverwrite(null, key, data);


      // Acquire a cursor for the table.
      Cursor dbcp = db.openCursor(null, CursorConfig.DEFAULT);


      // Walk through the table, checking
      DatabaseEntry readkey = new DatabaseEntry();
      DatabaseEntry readdata = new DatabaseEntry();
      DatabaseEntry whoknows = new DatabaseEntry();


      /*
       * NOTE: Maybe want to change from user-buffer to DB buffer
       *       depending on the flag options.user_buffer (setReuseBuffer)
       * The old version set MALLOC/REALLOC here - not sure if it is the same.
       */


      TestUtils.DEBUGOUT("Dbc.get");
      while (dbcp.getNext(readkey, readdata, LockMode.DEFAULT) == OperationStatus.SUCCESS) {
        String key_string =
        new String(readkey.getData(), 0, readkey.getSize());
        String data_string =
        new String(readdata.getData(), 0, readkey.getSize());
        TestUtils.DEBUGOUT("Got: " + key_string + ": " + data_string);
        int len = key_string.length();
        if (len <= 0 || key_string.charAt(len-1) != 'x') {
          TestUtils.ERR("reread terminator is bad");
        }
        len--;
        long bit = (1 << len);
        if (len > count) {
          TestUtils.ERR("reread length is bad: expect " + count + " got "+ len + " (" + key_string + ")" );
        }
        else if (!data_string.equals(key_string)) {
          TestUtils.ERR("key/data don't match");
        }
        else if ((bitmap & bit) != 0) {
          TestUtils.ERR("key already seen");
        }
        else if ((expected & bit) == 0) {
          TestUtils.ERR("key was not expected");
        }
        else {
          bitmap |= bit;
          expected &= ~(bit);
          for (i=0; i<len; i++) {
            if (key_string.charAt(i) != ('0' + i)) {
              System.out.print(" got " + key_string
              + " (" + (int)key_string.charAt(i)
              + "), wanted " + i
              + " (" + (int)('0' + i)
              + ") at position " + i + "\n");
              TestUtils.ERR("key is corrupt");
            }
          }
        }
      }
      if (expected != 0) {
        System.out.print(" expected more keys, bitmap is: " + expected + "\n");
        TestUtils.ERR("missing keys in database");
      }


      dbcp.close();
      TestUtils.DEBUGOUT("options.save_db " + options.save_db + " options.database " + options.database);
      if(options.save_db == false)
          db.close(false);
      else if (options.database == null)
          options.database = db;

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