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 Summary

Constructors

Modifier	Constructor and Description
protected	MultiDimension()

Method Summary

Methods

Modifier and Type	Method and Description
int	compare(long[] a, long[] b)
int	deinterleave(int dimensions, long scalar, int dim) Gets one of the original multi-dimensional values from a scalar value.
String	generatePreparedQuery(String table, String scalarColumn, String[] columns) Generates an optimized multi-dimensional range query.
static MultiDimension	getInstance() Get the singleton.
int	getMaxValue(int dimensions) Get the maximum value for the given dimension count.
ResultSet	getResult(PreparedStatement prep, int[] min, int[] max) Executes a prepared query that was generated using generatePreparedQuery.
long	interleave(int... values) Convert the multi-dimensional value into a one-dimensional (scalar) value.
long	interleave(int x, int y) Convert the two-dimensional value into a one-dimensional (scalar) value.
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.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

equals

Constructor Detail

MultiDimension

protected MultiDimension()

Method Detail

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

compare

public int compare(long[] a,
          long[] b)

Specified by:

compare in interface Comparator<long[]>