org.h2.tools
Class MultiDimension

java.lang.Object
  org.h2.tools.MultiDimension

All Implemented Interfaces:

java.util.Comparator<long[]>

public class MultiDimension
extends java.lang.Object
implements java.util.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).

Method Summary

int	compare(long[] a, long[] b)
int	deinterleave(long scalar, int dimensions, int dim) Gets one of the original multi-dimensional values from a scalar value.
java.lang.String	generatePreparedQuery(java.lang.String table, java.lang.String scalarColumn, java.lang.String[] columns) Generates an optimized multi-dimensional range query.
static MultiDimension	getInstance() Get the singleton.
java.sql.ResultSet	getResult(java.sql.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.

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

Method Detail

getInstance

public static MultiDimension getInstance()

Get the singleton.

Returns:

the singleton

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 bigger or equal to 0. The maximum value is dependent on the number of dimensions. For two keys, it is 32 bit, for 3: 21 bit, 4: 16 bit, 5: 12 bit, 6: 10 bit, 7: 9 bit, 8: 8 bit.

Parameters:

values - the multi-dimensional value

Returns:

the scalar value

deinterleave

public int deinterleave(long scalar,
                        int dimensions,
                        int dim)

Gets one of the original multi-dimensional values from a scalar value.

Parameters:

scalar - the scalar value

dimensions - the number of dimensions

dim - the dimension of the returned value (starting from 0)

Returns:

the value

generatePreparedQuery

public java.lang.String generatePreparedQuery(java.lang.String table,
                                              java.lang.String scalarColumn,
                                              java.lang.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 java.sql.ResultSet getResult(java.sql.PreparedStatement prep,
                                    int[] min,
                                    int[] max)
                             throws java.sql.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:

java.sql.SQLException

compare

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

Specified by:

compare in interface java.util.Comparator<long[]>