Package org.apache.druid.query.groupby.epinephelinae.column

Class FixedWidthGroupByColumnSelectorStrategy<T>

  • Type Parameters:
    T - Class of the dimension
    All Implemented Interfaces:
    ColumnSelectorStrategy, GroupByColumnSelectorStrategy
    @NotThreadSafe
public class FixedWidthGroupByColumnSelectorStrategy<T>
extends Object
implements GroupByColumnSelectorStrategy
    Strategy for grouping dimensions which have fixed-width objects. It is only used for numeric primitive types, however complex types can reuse this strategy if they can hint the engine that they are always fixed width (for e.g. IP types). Such types donot need to be backed by a dictionary, and hence are faster to group by.

    • Method Detail

      • getGroupingKeySizeBytes

        public int getGroupingKeySizeBytes()
        Description copied from interface: GroupByColumnSelectorStrategy
        Return the size, in bytes, of this dimension's values in the grouping key. For example, a String implementation would return 4, the size of an int.
        Specified by:
        getGroupingKeySizeBytes in interface GroupByColumnSelectorStrategy
        Returns:
        size, in bytes, of this dimension's values in the grouping key.

      • processValueFromGroupingKey

        public void processValueFromGroupingKey​(GroupByColumnSelectorPlus selectorPlus,
                                        ByteBuffer key,
                                        ResultRow resultRow,
                                        int keyBufferPosition)
        Description copied from interface: GroupByColumnSelectorStrategy
        Read a value from a grouping key and add it to the group by query result row, using the output name specified in a DimensionSpec. An implementation may choose to not add anything to the result row (e.g., as the String implementation does for empty rows) selectorPlus provides access to: - the keyBufferPosition offset from which to read the value - the dimension value selector - the DimensionSpec for this dimension from the query
        Specified by:
        processValueFromGroupingKey in interface GroupByColumnSelectorStrategy
        Parameters:
        selectorPlus - dimension info containing the key offset, value selector, and dimension spec
        key - grouping key
        resultRow - result row for the group by query being served
        keyBufferPosition - buffer position for the grouping key, added to support chaining multiple ColumnSelectorStrategy

      • initColumnValues

        public int initColumnValues​(ColumnValueSelector selector,
                            int columnIndex,
                            Object[] valuess)
        Description copied from interface: GroupByColumnSelectorStrategy
        Retrieve a row object from the ColumnValueSelector and put it in valuess at columnIndex.
        Specified by:
        initColumnValues in interface GroupByColumnSelectorStrategy
        Parameters:
        selector - Value selector for a column.
        columnIndex - Index of the column within the row values array
        valuess - Row values array, one index per column
        Returns:
        estimated increase in internal state footprint, in bytes, as a result of this operation. May be zero if memory did not increase as a result of this operation. Will not be negative.

      • initGroupingKeyColumnValue

        public void initGroupingKeyColumnValue​(int keyBufferPosition,
                                       int dimensionIndex,
                                       Object rowObj,
                                       ByteBuffer keyBuffer,
                                       int[] stack)
        Description copied from interface: GroupByColumnSelectorStrategy
        Read the first value within a row values object (e. g. IndexedInts, as the value in a dictionary-encoded string column) and write that value to the keyBuffer at keyBufferPosition. If the row size is 0 (e. g. IndexedInts.size()), write GroupByColumnSelectorStrategy.GROUP_BY_MISSING_VALUE instead. If the size of the row is > 0, write 1 to stack[] at columnIndex, otherwise write 0.
        Specified by:
        initGroupingKeyColumnValue in interface GroupByColumnSelectorStrategy
        Parameters:
        keyBufferPosition - Starting offset for this column's value within the grouping key.
        dimensionIndex - Index of this dimension within the stack array
        rowObj - Row value object for this column
        keyBuffer - grouping key
        stack - array containing the current within-row value index for each column

      • checkRowIndexAndAddValueToGroupingKey

        public boolean checkRowIndexAndAddValueToGroupingKey​(int keyBufferPosition,
                                                     Object rowObj,
                                                     int rowValIdx,
                                                     ByteBuffer keyBuffer)
        This is used for multi-valued dimensions, for values after the first one. None of the current types supported by this strategy handle multi-valued dimensions, therefore this short circuits and returns false
        Specified by:
        checkRowIndexAndAddValueToGroupingKey in interface GroupByColumnSelectorStrategy
        Parameters:
        keyBufferPosition - Starting offset for this column's value within the grouping key.
        rowObj - Row value object for this column (e.g., IndexedInts)
        rowValIdx - Index of the current value being grouped on within the row
        keyBuffer - grouping key
        Returns:
        true if rowValIdx < size of rowObj, false otherwise

      • writeToKeyBuffer

        public int writeToKeyBuffer​(int keyBufferPosition,
                            ColumnValueSelector selector,
                            ByteBuffer keyBuffer)
        Description copied from interface: GroupByColumnSelectorStrategy
        Write a single object from the given selector to the keyBuffer at keyBufferPosition. The reading column must have a single value. The position of the keyBuffer may be modified.
        Specified by:
        writeToKeyBuffer in interface GroupByColumnSelectorStrategy
        Parameters:
        keyBufferPosition - starting offset for this column's value within the grouping key
        selector - selector to retrieve row value object from
        keyBuffer - grouping key
        Returns:
        estimated increase in internal state footprint, in bytes, as a result of this operation. May be zero if memory did not increase as a result of this operation. Will not be negative.