Package org.apache.druid.segment

Interface TopNOptimizationInspector

All Known Implementing Classes:
SimpleTopNOptimizationInspector
public interface TopNOptimizationInspector
oddly specific Segment inspector for topN optimizations

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    areAllDictionaryIdsPresent()
    Returns true if all values in the dictionary are present in rows.

  • Method Details

    • areAllDictionaryIdsPresent

      boolean areAllDictionaryIdsPresent()
      Returns true if all values in the dictionary are present in rows. Returns false such as this segment can filter some rows out even if the query does not specify a filter, making the actual column cardinality be lower than what DimensionDictionarySelector.getValueCardinality() returns. Dimension selectors for such cursors can return non-contiguous dictionary IDs because the dictionary IDs in filtered rows will not be returned. Note that the number of rows accessible via cursors created on these segments will not necessarily decrease because of the built-in filters. For inner joins, for example, the number of joined rows can be larger than the number of rows in the base segment even though this method returns false.