Examples of org.apache.derby.iapi.store.access.SortObserver

Package org.apache.derby.iapi.store.access

Examples of org.apache.derby.iapi.store.access.SortObserver

org.apache.derby.iapi.store.access.SortObserver
A SortObserver is an object that is used as a callback by the sorter. It allows the sort client to do whatever they want from the context of a sort. It contains 2 callback methods: insertDuplicateKey() and insertNonDuplicateKey(). On each SortController.insert(), one or the other of these methods will be called, depending on whether the given row has a key that has been seen before or not.
Some sample uses include:
- Sorts from Language: Language typically recycles data type wrappers. So the language layer uses SortObservers to clone rows that are kept by the sorter.
- Distinct sorts: The sorter will call the sort observer each time it identifies a duplicate row. Based on what the sort observer returns to the sorter, the sorter will either retain (insert) the duplicate row, or discard the duplicate row. All you have to do to implement a distinct sort is to tell the sorter to discard the row (return null from insertDuplicateKey()). Also, if you want to throw an exception on a duplicate (e.g. create a unique index), you can just throw an exception from your SortObserver.
- Aggregates: Vector (grouped) aggregates typically require a sort. Language can use a SortObserver to perform aggregations as duplicate elements are encountered. Scalar aggregates can also be computed using a SortObserver.
These are possible uses only. You, kind reader, may do whatever you wish with this forgiving interface. @see SortController

       * we could get in a situation where 1 sort reuses a
       * wrapper that is still in use in another sort.
       */
      boolean reuseWrappers = (numIndexes == 1);


      SortObserver    sortObserver = 
                new BasicSortObserver(
                        false, false, indexRows[index], reuseWrappers);


      ordering[index] = new ColumnOrdering[numColumnOrderings];
      for (int ii =0; ii < numColumnOrderings - 1; ii++)

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    ** we'll feed this into the sorter again w/o the distinct
    ** column in the ordering list.
    */
    GenericAggregator[] aggsNoDistinct = getSortAggregators(aggInfoList, true,
        activation.getLanguageConnectionContext(), source);
    SortObserver sortObserver = new AggregateSortObserver(true, aggsNoDistinct, aggregates,
                                sortTemplateRow);


    sortId = tc.createSort((Properties)null, 
          sortTemplateRow.getRowArray(),
          order,

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      int[] baseColumnPositions = 
                constants.irgs[index].baseColumnPositions();
      boolean[] isAscending     = constants.irgs[index].isAscending();
           
      int numColumnOrderings;
      SortObserver sortObserver = null;


      /* We can only reuse the wrappers when doing an
       * external sort if there is only 1 index.  Otherwise,
       * we could get in a situation where 1 sort reuses a
       * wrapper that is still in use in another sort.

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      // Get the ConglomerateDescriptor for the index
      cd = td.getConglomerateDescriptor(constants.indexCIDS[index]);
      int[] baseColumnPositions = constants.irgs[index].baseColumnPositions();
      boolean[] isAscending = constants.irgs[index].isAscending();
      int numColumnOrderings;
      SortObserver sortObserver = null;
      if (cd.getIndexDescriptor().isUnique())
      {
        numColumnOrderings = baseColumnPositions.length;
        String[] columnNames = getColumnNames(baseColumnPositions);

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    ExecRow         inputRow;
    int            inputRowCountEstimate = (int) optimizerEstimatedRowCount;


    tc = getTransactionController();


    SortObserver observer;
    if (usingAggregateObserver)
      observer = new AggregateSortObserver(true, aggregates,
        aggregates, sortTemplateRow);
    else
      observer = new BasicSortObserver(true, false,

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       * We create a basic sort observer for non-unique indexes
       * so that we can reuse the wrappers during an external
       * sort.
       */
      int             numColumnOrderings;
      SortObserver    sortObserver   = null;
            Properties      sortProperties = null;
      if (unique || uniqueWithDuplicateNulls)
      {
        // if the index is a constraint, use constraintname in 
                // possible error message

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       * we could get in a situation where 1 sort reuses a
       * wrapper that is still in use in another sort.
       */
      boolean reuseWrappers = (numIndexes == 1);


      SortObserver    sortObserver = 
                new BasicSortObserver(
                        false, false, indexRows[index], reuseWrappers);


      ordering[index] = new ColumnOrdering[numColumnOrderings];
      for (int ii =0; ii < numColumnOrderings - 1; ii++)

View Full Code Here

      int[] baseColumnPositions = 
                constants.irgs[index].baseColumnPositions();
      boolean[] isAscending     = constants.irgs[index].isAscending();
           
      int numColumnOrderings;
      SortObserver sortObserver = null;


      /* We can only reuse the wrappers when doing an
       * external sort if there is only 1 index.  Otherwise,
       * we could get in a situation where 1 sort reuses a
       * wrapper that is still in use in another sort.

View Full Code Here

      // Get the ConglomerateDescriptor for the index
      cd = td.getConglomerateDescriptor(constants.indexCIDS[index]);
      int[] baseColumnPositions = constants.irgs[index].baseColumnPositions();
      boolean[] isAscending = constants.irgs[index].isAscending();
      int numColumnOrderings;
      SortObserver sortObserver = null;
      if (cd.getIndexDescriptor().isUnique())
      {
        numColumnOrderings = baseColumnPositions.length;
        String[] columnNames = getColumnNames(baseColumnPositions);

View Full Code Here

       * we could get in a situation where 1 sort reuses a
       * wrapper that is still in use in another sort.
       */
      boolean reuseWrappers = (numIndexes == 1);


      SortObserver    sortObserver = 
                new BasicSortObserver(
                        false, false, indexRows[index], reuseWrappers);


      ordering[index] = new ColumnOrdering[numColumnOrderings];
      for (int ii =0; ii < numColumnOrderings - 1; ii++)

View Full Code Here

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