Package org.h2.command.query

Class SelectGroups

  • Direct Known Subclasses:
    SelectGroups.Grouped, SelectGroups.Plain
    public abstract class SelectGroups
extends java.lang.Object
    Grouped data for aggregates.

    Call sequence:

    Call sequence for lazy group sorted result:

    • resetLazy() (not required before the first execution).
    • For each source group nextLazyGroup() should be invoked.
    • For each source row nextLazyRow() should be invoked. Each group can have one or more rows.

    • Field Detail

      • expressions

        final java.util.ArrayList<Expression> expressions
        The query's column list, including invisible expressions such as order by expressions.

      • currentGroupByExprData

        java.lang.Object[] currentGroupByExprData
        The array of current group-by expression data e.g. AggregateData.

      • exprToIndexInGroupByData

        private final java.util.HashMap<Expression,​java.lang.Integer> exprToIndexInGroupByData
        Maps an expression object to an index, to use in accessing the Object[] pointed to by groupByData.

      • windowPartitionData

        private final java.util.HashMap<DataAnalysisOperation,​java.util.TreeMap<Value,​PartitionData>> windowPartitionData
        Maps an partitioned window expression object to its data.

      • currentGroupRowId

        int currentGroupRowId
        The id of the current group.

    • Method Detail

      • getInstance

        public static SelectGroups getInstance​(SessionLocal session,
                                       java.util.ArrayList<Expression> expressions,
                                       boolean isGroupQuery,
                                       int[] groupIndex)
        Creates new instance of grouped data.
        Parameters:
        session - the session
        expressions - the expressions
        isGroupQuery - is this query is a group query
        groupIndex - the indexes of group expressions, or null
        Returns:
        new instance of the grouped data.

      • isCurrentGroup

        public boolean isCurrentGroup()
        Is there currently a group-by active.
        Returns:
        true if there is currently a group-by active, otherwise returns false.

      • getCurrentGroupExprData

        public final java.lang.Object getCurrentGroupExprData​(Expression expr)
        Get the group-by data for the current group and the passed in expression.
        Parameters:
        expr - expression
        Returns:
        expression data or null

      • setCurrentGroupExprData

        public final void setCurrentGroupExprData​(Expression expr,
                                          java.lang.Object obj)
        Set the group-by data for the current group and the passed in expression.
        Parameters:
        expr - expression
        obj - expression data to set

      • createRow

        final java.lang.Object[] createRow()
        Creates new object arrays to holds group-by data.
        Returns:
        new object array to holds group-by data.

      • getWindowExprData

        public final PartitionData getWindowExprData​(DataAnalysisOperation expr,
                                             Value partitionKey)
        Get the window data for the specified expression.
        Parameters:
        expr - expression
        partitionKey - a key of partition
        Returns:
        expression data or null

      • setWindowExprData

        public final void setWindowExprData​(DataAnalysisOperation expr,
                                    Value partitionKey,
                                    PartitionData obj)
        Set the window data for the specified expression.
        Parameters:
        expr - expression
        partitionKey - a key of partition
        obj - window expression data to set

      • updateCurrentGroupExprData

        abstract void updateCurrentGroupExprData()
        Update group-by data specified by implementation.

      • getCurrentGroupRowId

        public int getCurrentGroupRowId()
        Returns identity of the current row. Used by aggregates to check whether they already processed this row or not.
        Returns:
        identity of the current row

      • reset

        public void reset()
        Resets this group data for reuse.

      • nextSource

        public abstract void nextSource()
        Invoked for each source row to evaluate group key and setup all necessary data for aggregates.

      • done

        public void done()
        Invoked after all source rows are evaluated.

      • next

        public abstract ValueRow next()
        Returns the key of the next group.
        Returns:
        the key of the next group, or null

      • remove

        public void remove()
        Removes the data for the current key.
        See Also:
        next()

      • resetLazy

        public void resetLazy()
        Resets this group data for reuse in lazy mode.

      • nextLazyGroup

        public void nextLazyGroup()
        Moves group data to the next group in lazy mode.

      • nextLazyRow

        public void nextLazyRow()
        Moves group data to the next row in lazy mode.