Examples of com.sleepycat.je.JoinCursor

com.sleepycat.je.JoinCursor
ialize key for secondary index 1 OperationStatus status1 = cursor1.getSearchKey(key, data, LockMode.DEFAULT); key.setData(...); // initialize key for secondary index 2 OperationStatus status2 = cursor2.getSearchKey(key, data, LockMode.DEFAULT);
if (status1 == OperationStatus.SUCCESS && status2 == OperationStatus.SUCCESS) {
SecondaryCursor[] cursors = {cursor1, cursor2}; joinCursor = primaryDb.join(cursors, null);
while (true) { OperationStatus joinStatus = joinCursor.getNext(key, data, LockMode.DEFAULT); if (joinStatus == OperationStatus.SUCCESS) { // Do something with the key and data. } else { break; } } } } finally { if (cursor1 != null) { cursor1.close(); } if (cursor2 != null) { cursor2.close(); } if (joinCursor != null) { joinCursor.close(); } }
The join algorithm is described here so that its cost can be estimated and compared to other approaches for performing a query. Say that N cursors are provided for the join operation. According to the order they appear in the array the cursors are labeled C(1) through C(n), and the keys at each cursor position are labeled K(1) through K(n).
1. Using C(1), the join algorithm iterates sequentially through all records having K(1). This iteration is equivalent to a {@link Cursor#getNextDup Cursor.getNextDup} operation on the secondary index. The primary key of acandidate record is determined in this manner. The primary record itself is not retrieved and the primary database is not accessed.
2. For each candidate primary key found in step 1, a Btree lookup is performed using C(2) through C(n), in that order. The Btree lookups are exact searches to determine whether the candidate record also contains secondary keys K(2) through K(n). The lookups are equivalent to a {@link Cursor#getSearchBoth Cursor.getSearchBoth} operation on the secondary index.The primary record itself is not retrieved and the primary database is not accessed.
3. If any lookup in step 2 fails, the algorithm advances to the next candidate record using C(1). Lookups are performed in the order of the cursor array, and the algorithm proceeds to the next C(1) candidate key as soon as a single lookup fails.
4. If all lookups in step 2 succeed, then the matching key and/or data is returned by the {@code getNext} method. If the {@link #getNext(DatabaseEntry,DatabaseEntry,LockMode)} method signature is used,then the primary database is read to obtain the record data, as if {@link Cursor#getSearchKey Cursor.getSearchKey} were called for the primarydatabase. If the {@link #getNext(DatabaseEntry,LockMode)} method signatureis used, then only the primary key is returned and the primary database is not accessed.
5. The algorithm ends when C(1) has no more candidate records with K(1), and the {@code getNext} method will then return {@link com.sleepycat.je.OperationStatus#NOTFOUND OperationStatus.NOTFOUND}.

     */
    void close()
        throws DatabaseException {


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

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          SecondaryCursor cursor = db.openSecondaryCursor(null, null);
          key.setData(o.getBytes());
          cursor.getSearchKey(key, data, null);
          cursors[i] = cursor;
        }
        JoinCursor joinCursor = dbMain.join(cursors, null);
        try {
          while (joinCursor.getNext(key, null) == OperationStatus.SUCCESS) {
            entries.add(key);
            key = new DatabaseEntry();
          }
        } finally {
          joinCursor.close();
        }
      } finally {
        for (SecondaryCursor cursor : cursors) {
          if (cursor == null) {
            break;

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                assertEquals(msg, OperationStatus.SUCCESS, status);
            }
            for (int j = 0; j < 2; j += 1) {
                boolean withData = (j == 0);
                JoinConfig config = (j == 0) ? null : joinConfigNoSort;
                JoinCursor jc = priDb.join(cursors, config);
                assertSame(priDb, jc.getDatabase());
                for (int k = 0; k < priKeys.length; k += 1) {
                    String msg = prefix + " k=" + k + " pkey=" + priKeys[k];
                    if (withData) {
                        status = jc.getNext(key, data, LockMode.DEFAULT);
                    } else {
                        status = jc.getNext(key, LockMode.DEFAULT);
                    }
                    assertEquals(msg, OperationStatus.SUCCESS, status);
                    assertEquals(msg, priKeys[k], (int) key.getData()[0]);
                    if (withData) {
                        boolean dataFound = false;
                        for (int m = 0; m < dataSet.length; m += 2) {
                            int[] vals = dataSet[m];
                            int priKey = dataSet[m + 1][0];
                            if (priKey == priKeys[k]) {
                                for (int n = 0; n < 3; n += 1) {
                                    assertEquals(msg, vals[n],
                                                 (int) data.getData()[n]);
                                    dataFound = true;;
                                }
                            }
                        }
                        assertTrue(msg, dataFound);
                    }
                }
                String msg = prefix + " no more expected";
                if (withData) {
                    status = jc.getNext(key, data, LockMode.DEFAULT);
                } else {
                    status = jc.getNext(key, LockMode.DEFAULT);
                }
                assertEquals(msg, OperationStatus.NOTFOUND, status);


                Cursor[] sorted = DbInternal.getSortedCursors(jc);
                assertEquals(CURSOR_ORDER.length, sorted.length);
                if (config == joinConfigNoSort) {
                    Database db0 = sorted[0].getDatabase();
                    Database db1 = sorted[1].getDatabase();
                    Database db2 = sorted[2].getDatabase();
                    assertSame(db0, secDb0);
                    assertSame(db1, secDb1);
                    assertSame(db2, secDb2);
                } else if (setNum == CURSOR_ORDER_SET) {
                    Database db0 = sorted[CURSOR_ORDER[0]].getDatabase();
                    Database db1 = sorted[CURSOR_ORDER[1]].getDatabase();
                    Database db2 = sorted[CURSOR_ORDER[2]].getDatabase();
                    assertSame(db0, secDb0);
                    assertSame(db1, secDb1);
                    assertSame(db2, secDb2);
                }
                jc.close();
            }
        }


        c0.close();
        c1.close();

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     */
    void close()
        throws DatabaseException {


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

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     */
    void close()
        throws DatabaseException {


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

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