Package edu.caltech.nanodb.queryeval

Class ColumnStats

  • public class ColumnStats
extends java.lang.Object
    This class holds some useful statistics for a specific column. At present this consists of the following:
    • the number of unique values in the column (not including NULL in the count)
    • the number of NULL values in the column
    • the minimum value for the column
    • the maximum value for the column
    The ColumnStatsCollector class can be used to easily collect these statistics for a particular column of a table.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private java.lang.Object maxValue
      The maximum value of this column in the table, or null if the maximum value is unknown.
      private java.lang.Object minValue
      The minimum value of this column in the table, or null if the minimum value is unknown.
      private int numNullValues
      The total number of NULL values for this column in the table, or -1 if the total number of NULL values is unknown.
      private int numUniqueValues
      The total number of unique values for this column in the table, or -1 if the total number of unique values is unknown.

    • Constructor Summary

      Constructors 
      Constructor Description
      ColumnStats()
      Initializes a column-stats object to all "unknown" values.
      ColumnStats​(int numUniqueValues, int numNullValues, java.lang.Object minValue, java.lang.Object maxValue)
      Initializes a column-stats object with the specified values.
      ColumnStats​(ColumnStats stats)
      Copies another column-stats object into this object.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.Object getMaxValue()
      Returns the maximum value for the column.
      java.lang.Object getMinValue()
      Returns the minimum value for the column.
      int getNumNullValues()
      Returns the number of NULL values for the column, or -1 if the number is unknown
      int getNumUniqueValues()
      Returns the number of unique values for the column, or -1 if the number is unknown
      boolean hasDifferentMinMaxValues()
      Returns true if this column-stats object has both minimum and maximum values, and they are actually different values.
      boolean hasMinMaxValues()
      Returns true if this column-stats object has both minimum and maximum values.
      void setMaxValue​(java.lang.Object maxValue)
      Sets the maximum value for the column.
      void setMinValue​(java.lang.Object minValue)
      Sets the minimum value for the column.
      void setNumNullValues​(int num)
      Sets the number of NULL values for the column.
      void setNumUniqueValues​(int num)
      Sets the number of unique values for the column.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • numUniqueValues

        private int numUniqueValues
        The total number of unique values for this column in the table, or -1 if the total number of unique values is unknown.

      • numNullValues

        private int numNullValues
        The total number of NULL values for this column in the table, or -1 if the total number of NULL values is unknown.

      • minValue

        private java.lang.Object minValue
        The minimum value of this column in the table, or null if the minimum value is unknown.

      • maxValue

        private java.lang.Object maxValue
        The maximum value of this column in the table, or null if the maximum value is unknown.

    • Constructor Detail

      • ColumnStats

        public ColumnStats​(int numUniqueValues,
                   int numNullValues,
                   java.lang.Object minValue,
                   java.lang.Object maxValue)
        Initializes a column-stats object with the specified values.
        Parameters:
        numUniqueValues - the number of unique values in the column, or -1 if unknown
        numNullValues - the number of NULL values in the column, or -1 if unknown
        minValue - the minimum value in the column, or null if unknown
        maxValue - the maximum value in the column, or null if unknown

      • ColumnStats

        public ColumnStats()
        Initializes a column-stats object to all "unknown" values.

      • ColumnStats

        public ColumnStats​(ColumnStats stats)
        Copies another column-stats object into this object.

    • Method Detail

      • getNumUniqueValues

        public int getNumUniqueValues()
        Returns the number of unique values for the column, or -1 if the number is unknown
        Returns:
        the number of unique values for the column, or -1 if the number is unknown

      • setNumUniqueValues

        public void setNumUniqueValues​(int num)
        Sets the number of unique values for the column.
        Parameters:
        num - the number of unique values in the table for the column, or -1 if the number if unknown

      • getNumNullValues

        public int getNumNullValues()
        Returns the number of NULL values for the column, or -1 if the number is unknown
        Returns:
        the number of NULL values for the column, or -1 if the number is unknown

      • setNumNullValues

        public void setNumNullValues​(int num)
        Sets the number of NULL values for the column.
        Parameters:
        num - the number of NULL values in the table for the column, or -1 if the number if unknown

      • getMinValue

        public java.lang.Object getMinValue()
        Returns the minimum value for the column.
        Returns:
        the minimum value in the table for the column

      • setMinValue

        public void setMinValue​(java.lang.Object minValue)
        Sets the minimum value for the column.
        Parameters:
        minValue - the minimum value in the table for the column

      • getMaxValue

        public java.lang.Object getMaxValue()
        Returns the maximum value for the column.
        Returns:
        the maximum value in the table for the column

      • setMaxValue

        public void setMaxValue​(java.lang.Object maxValue)
        Sets the maximum value for the column.
        Parameters:
        maxValue - the maximum value in the table for the column

      • hasMinMaxValues

        public boolean hasMinMaxValues()
        Returns true if this column-stats object has both minimum and maximum values.
        Returns:
        true if this column-stats object has both minimum and maximum values

      • hasDifferentMinMaxValues

        public boolean hasDifferentMinMaxValues()
        Returns true if this column-stats object has both minimum and maximum values, and they are actually different values.
        Returns:
        true if this column-stats object has both minimum and maximum values, and they are actually different values.