Package org.apache.derby.impl.sql.execute

Class GroupedAggregateResultSet

  • All Implemented Interfaces:
    CursorResultSet, NoPutResultSet, ResultSet, RowLocationRetRowSource, RowSource
    Direct Known Subclasses:
    DistinctGroupedAggregateResultSet
    class GroupedAggregateResultSet
extends GenericAggregateResultSet
implements CursorResultSet
    This ResultSet evaluates grouped, non distinct aggregates. It will scan the entire source result set and calculate the grouped aggregates when scanning the source during the first call to next(). The implementation is capable of computing multiple levels of grouping in a single result set (this is requested using GROUP BY ROLLUP). This implementation has 3 variations, which it chooses according to the following rules: - If the data are guaranteed to arrive already in sorted order, we make a single pass over the data, computing the aggregates in-line as the data are read. - If the statement requests either multiple ROLLUP levels, or a DISTINCT grouping, then the data are first sorted, then we make a single pass over the data as above. - Otherwise, the data are sorted, and a SortObserver is used to compute the aggregations inside the sort, and the results are read back directly from the sorter. Note that, as of the introduction of the ROLLUP support, we no longer ALWAYS compute the aggregates using a SortObserver, which is an arrangement by which the sorter calls back into the aggregates during the sort process each time it consolidates two rows with the same sort key. Using aggregate sort observers is an efficient technique, but it was complex to extend it to the ROLLUP case, so to simplify the code we just have one path for both already-sorted and un-sorted data sources in the ROLLUP case.

    • Field Detail

      • rowsInput

        public int rowsInput

      • rowsReturned

        public int rowsReturned

      • hasDistinctAggregate

        public boolean hasDistinctAggregate

      • isInSortedOrder

        public boolean isInSortedOrder

      • numDistinctAggs

        private int numDistinctAggs

      • maxRowSize

        private int maxRowSize

      • sourceExecIndexRow

        private ExecIndexRow sourceExecIndexRow

      • resultsComplete

        private boolean resultsComplete

      • finishedResults

        private java.util.List<ExecRow> finishedResults

      • distinctValues

        private java.util.List<java.util.List<java.util.Set<DataValueDescriptor>>> distinctValues

      • rollup

        private boolean rollup

      • usingAggregateObserver

        private boolean usingAggregateObserver

      • genericSortId

        private long genericSortId

      • sortProperties

        public java.util.Properties sortProperties

    • Constructor Detail

      • GroupedAggregateResultSet

        GroupedAggregateResultSet​(NoPutResultSet s,
                          boolean isInSortedOrder,
                          int aggregateItem,
                          int orderingItem,
                          Activation a,
                          int ra,
                          int maxRowSize,
                          int resultSetNumber,
                          double optimizerEstimatedRowCount,
                          double optimizerEstimatedCost,
                          boolean isRollup)
                   throws StandardException
        Constructor
        Parameters:
        s - input result set
        isInSortedOrder - true if the source results are in sorted order
        aggregateItem - indicates the number of the SavedObject off of the PreparedStatement that holds the AggregatorInfoList used by this routine.
        orderingItem - indicates the number of the SavedObject off of the PreparedStatement that holds the ColumOrdering array used by this routine
        a - activation
        ra - saved object that builds an empty output row
        maxRowSize - approx row size, passed to sorter
        resultSetNumber - The resultSetNumber for this result set
        Throws:
        StandardException - Thrown on error