weka.core.converters

Class DatabaseLoader

java.lang.Object

weka.core.converters.AbstractLoader

weka.core.converters.DatabaseLoader

All Implemented Interfaces:

Serializable, BatchConverter, DatabaseConverter, IncrementalConverter, Loader, OptionHandler, RevisionHandler

public class DatabaseLoader
extends AbstractLoader
implements BatchConverter, IncrementalConverter, DatabaseConverter, OptionHandler

Reads Instances from a Database. Can read a database in batch or incremental mode.
In inremental mode MySQL and HSQLDB are supported.
For all other DBMS set a pseudoincremental mode is used:
In pseudo incremental mode the instances are read into main memory all at once and then incrementally provided to the user.
For incremental loading the rows in the database table have to be ordered uniquely.
The reason for this is that every time only a single row is fetched by extending the user query by a LIMIT clause.
If this extension is impossible instances will be loaded pseudoincrementally. To ensure that every row is fetched exaclty once, they have to ordered.
Therefore a (primary) key is necessary.This approach is chosen, instead of using JDBC driver facilities, because the latter one differ betweeen different drivers.
If you use the DatabaseSaver and save instances by generating automatically a primary key (its name is defined in DtabaseUtils), this primary key will be used for ordering but will not be part of the output. The user defined SQL query to extract the instances should not contain LIMIT and ORDER BY clauses (see -Q option).
In addition, for incremental loading, you can define in the DatabaseUtils file how many distinct values a nominal attribute is allowed to have. If this number is exceeded, the column will become a string attribute.
In batch mode no string attributes will be created.

Valid options are:

 -url <JDBC URL>
  The JDBC URL to connect to.
  (default: from DatabaseUtils.props file)

 -user <name>
  The user to connect with to the database.
  (default: none)

 -password <password>
  The password to connect with to the database.
  (default: none)

 -Q <query>
  SQL query of the form
   SELECT <list of columns>|* FROM <table> [WHERE]
  to execute.
  (default: Select * From Results0)

 -P <list of column names>
  List of column names uniquely defining a DB row
  (separated by ', ').
  Used for incremental loading.
  If not specified, the key will be determined automatically,
  if possible with the used JDBC driver.
  The auto ID column created by the DatabaseSaver won't be loaded.

 -I
  Sets incremental loading

Version:

$Revision: 11199 $

Author:

Stefan Mutter (mutter@cs.waikato.ac.nz)

See Also:

Loader, Serialized Form

Field Summary

Fields inherited from interface weka.core.converters.Loader

BATCH, INCREMENTAL, NONE

Constructor Summary

Constructors

Constructor and Description
DatabaseLoader() Constructor

Method Summary

Modifier and Type	Method and Description
void	connectToDatabase() Opens a connection to the database
Instances	getDataSet() Return the full data set in batch mode (header and all intances at once).
String	getKeys() Gets the key columns' name
Instance	getNextInstance(Instances structure) Read the data set incrementally---get the next instance in the data set or returns null if there are no more instances to get.
String[]	getOptions() Gets the setting
String	getPassword() Returns the database password
String	getQuery() Gets the query to execute against the database
String	getRevision() Returns the revision string.
Instances	getStructure() Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.
String	getUrl() Gets the URL
String	getUser() Gets the user name
String	globalInfo() Returns a string describing this Loader
String	keysTipText() the tip text for this property
Enumeration	listOptions() Lists the available options
static void	main(String[] options) Main method.
String	passwordTipText() the tip text for this property
String	queryTipText() the tip text for this property
void	reset() Resets the Loader ready to read a new data set
void	resetStructure() Resets the structure of instances
void	setKeys(String keys) Sets the key columns of a database table
void	setOptions(String[] options) Sets the options.
void	setPassword(String password) Sets user password for the database
void	setQuery(String q) Sets the query to execute against the database
void	setSource() Sets the database url using the DatabaseUtils file
void	setSource(String url) Sets the database url
void	setSource(String url, String userName, String password) Sets the database url, user and pw
void	setUrl(String url) Sets the database URL
void	setUser(String user) Sets the database user
String	urlTipText() the tip text for this property
String	userTipText() the tip text for this property

Methods inherited from class weka.core.converters.AbstractLoader

setRetrieval, setSource, setSource

Methods inherited from class java.lang.Object

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

Constructor Detail

DatabaseLoader

public DatabaseLoader()
               throws Exception

Constructor

Throws:

Exception - if initialization fails

Method Detail

globalInfo

public String globalInfo()

Returns a string describing this Loader

Returns:

a description of the Loader suitable for displaying in the explorer/experimenter gui

reset

public void reset()
           throws Exception

Resets the Loader ready to read a new data set

Specified by:

reset in interface Loader

Overrides:

reset in class AbstractLoader

Throws:

Exception - if an error occurs while disconnecting from the database

resetStructure

public void resetStructure()

Resets the structure of instances

setQuery

public void setQuery(String q)

Sets the query to execute against the database

Parameters:

q - the query to execute

getQuery

public String getQuery()

Gets the query to execute against the database

Returns:

the query

queryTipText

public String queryTipText()

the tip text for this property

Returns:

the tip text

setKeys

public void setKeys(String keys)

Sets the key columns of a database table

Parameters:

keys - a String containing the key columns in a comma separated list.

getKeys

public String getKeys()

Gets the key columns' name

Returns:

name of the key columns'

keysTipText

public String keysTipText()

the tip text for this property

Returns:

the tip text

setUrl

public void setUrl(String url)

Sets the database URL

Specified by:

setUrl in interface DatabaseConverter

Parameters:

url - string with the database URL

getUrl

public String getUrl()

Gets the URL

Specified by:

getUrl in interface DatabaseConverter

Returns:

the URL

urlTipText

public String urlTipText()

the tip text for this property

Returns:

the tip text

setUser

public void setUser(String user)

Sets the database user

Specified by:

setUser in interface DatabaseConverter

Parameters:

user - the database user name

getUser

public String getUser()

Gets the user name

Specified by:

getUser in interface DatabaseConverter

Returns:

name of database user

userTipText

public String userTipText()

the tip text for this property

Returns:

the tip text

setPassword

public void setPassword(String password)

Sets user password for the database

Specified by:

setPassword in interface DatabaseConverter

Parameters:

password - the password

getPassword

public String getPassword()

Returns the database password

Returns:

the database password

passwordTipText

public String passwordTipText()

the tip text for this property

Returns:

the tip text

setSource

public void setSource(String url,
                      String userName,
                      String password)

Sets the database url, user and pw

Parameters:

url - the database url

userName - the user name

password - the password

setSource

public void setSource(String url)

Sets the database url

Parameters:

url - the database url

setSource

public void setSource()
               throws Exception

Sets the database url using the DatabaseUtils file

Throws:

Exception - if something goes wrong

connectToDatabase

public void connectToDatabase()

Opens a connection to the database

getStructure

public Instances getStructure()
                       throws IOException

Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.

Specified by:

getStructure in interface Loader

Specified by:

getStructure in class AbstractLoader

Returns:

the structure of the data set as an empty set of Instances

Throws:

IOException - if an error occurs

getDataSet

public Instances getDataSet()
                     throws IOException

Return the full data set in batch mode (header and all intances at once).

Specified by:

getDataSet in interface Loader

Specified by:

getDataSet in class AbstractLoader

Returns:

the structure of the data set as an empty set of Instances

Throws:

IOException - if there is no source or parsing fails

getNextInstance

public Instance getNextInstance(Instances structure)
                         throws IOException

Read the data set incrementally---get the next instance in the data set or returns null if there are no more instances to get. If the structure hasn't yet been determined by a call to getStructure then method does so before returning the next instance in the data set.

Specified by:

getNextInstance in interface Loader

Specified by:

getNextInstance in class AbstractLoader

Parameters:

structure - the dataset header information, will get updated in case of string or relational attributes

Returns:

the next instance in the data set as an Instance object or null if there are no more instances to be read

Throws:

IOException - if there is an error during parsing

getOptions

public String[] getOptions()

Gets the setting

Specified by:

getOptions in interface OptionHandler

Returns:

the current setting

listOptions

public Enumeration listOptions()

Lists the available options

Specified by:

listOptions in interface OptionHandler

Returns:

an enumeration of the available options

setOptions

public void setOptions(String[] options)
                throws Exception

Sets the options. Valid options are:

 -url <JDBC URL>
  The JDBC URL to connect to.
  (default: from DatabaseUtils.props file)

 -user <name>
  The user to connect with to the database.
  (default: none)

 -password <password>
  The password to connect with to the database.
  (default: none)

 -Q <query>
  SQL query of the form
   SELECT <list of columns>|* FROM <table> [WHERE]
  to execute.
  (default: Select * From Results0)

 -P <list of column names>
  List of column names uniquely defining a DB row
  (separated by ', ').
  Used for incremental loading.
  If not specified, the key will be determined automatically,
  if possible with the used JDBC driver.
  The auto ID column created by the DatabaseSaver won't be loaded.

 -I
  Sets incremental loading

Specified by:

setOptions in interface OptionHandler

Parameters:

options - the options

Throws:

Exception - if options cannot be set

getRevision

public String getRevision()

Returns the revision string.

Specified by:

getRevision in interface RevisionHandler

Returns:

the revision

main

public static void main(String[] options)

Main method.

Parameters:

options - the options