Package org.h2.tools

Class MultiDimension

java.lang.Object
org.h2.tools.MultiDimension
All Implemented Interfaces:
Comparator<long[]>
public class MultiDimension extends Object implements Comparator<long[]>
A tool to help an application execute multi-dimensional range queries. The algorithm used is database independent, the only requirement is that the engine supports a range index (for example b-tree).

  • Constructor Details

    • MultiDimension

      protected MultiDimension()
      Protected constructor

  • Method Details

    • getInstance

      public static MultiDimension getInstance()
      Get the singleton.
      Returns:
      the singleton

    • normalize

      public int normalize(int dimensions, double value, double min, double max)
      Normalize a value so that it is between the minimum and maximum for the given number of dimensions.
      Parameters:
      dimensions - the number of dimensions
      value - the value (must be in the range min..max)
      min - the minimum value
      max - the maximum value (must be larger than min)
      Returns:
      the normalized value in the range 0..getMaxValue(dimensions)

    • getMaxValue

      public int getMaxValue(int dimensions)
      Get the maximum value for the given dimension count. For two dimensions, each value must contain at most 32 bit, for 3: 21 bit, 4: 16 bit, 5: 12 bit, 6: 10 bit, 7: 9 bit, 8: 8 bit.
      Parameters:
      dimensions - the number of dimensions
      Returns:
      the maximum value

    • interleave

      public long interleave(int... values)
      Convert the multi-dimensional value into a one-dimensional (scalar) value. This is done by interleaving the bits of the values. Each values must be between 0 (including) and the maximum value for the given number of dimensions (getMaxValue, excluding). To normalize values to this range, use the normalize function.
      Parameters:
      values - the multi-dimensional value
      Returns:
      the scalar value

    • interleave

      public long interleave(int x, int y)
      Convert the two-dimensional value into a one-dimensional (scalar) value. This is done by interleaving the bits of the values. Each values must be between 0 (including) and the maximum value for the given number of dimensions (getMaxValue, excluding). To normalize values to this range, use the normalize function.
      Parameters:
      x - the value of the first dimension, normalized
      y - the value of the second dimension, normalized
      Returns:
      the scalar value

    • deinterleave

      public int deinterleave(int dimensions, long scalar, int dim)
      Gets one of the original multi-dimensional values from a scalar value.
      Parameters:
      dimensions - the number of dimensions
      scalar - the scalar value
      dim - the dimension of the returned value (starting from 0)
      Returns:
      the value

    • generatePreparedQuery

      public String generatePreparedQuery(String table, String scalarColumn, String[] columns)
      Generates an optimized multi-dimensional range query. The query contains parameters. It can only be used with the H2 database.
      Parameters:
      table - the table name
      columns - the list of columns
      scalarColumn - the column name of the computed scalar column
      Returns:
      the query

    • getResult

      public ResultSet getResult(PreparedStatement prep, int[] min, int[] max) throws SQLException
      Executes a prepared query that was generated using generatePreparedQuery.
      Parameters:
      prep - the prepared statement
      min - the lower values
      max - the upper values
      Returns:
      the result set
      Throws:
      SQLException - on failure

    • compare

      public int compare(long[] a, long[] b)
      Specified by:
      compare in interface Comparator<long[]>