Package weka.core.converters

Class DatabaseLoader

  • All Implemented Interfaces:
    java.io.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

    • Constructor Summary

      Constructors 
      Constructor Description
      DatabaseLoader()
      Constructor

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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).
      java.lang.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.
      java.lang.String[] getOptions()
      Gets the setting
      java.lang.String getPassword()
      Returns the database password
      java.lang.String getQuery()
      Gets the query to execute against the database
      java.lang.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.
      java.lang.String getUrl()
      Gets the URL
      java.lang.String getUser()
      Gets the user name
      java.lang.String globalInfo()
      Returns a string describing this Loader
      java.lang.String keysTipText()
      the tip text for this property
      java.util.Enumeration listOptions()
      Lists the available options
      static void main​(java.lang.String[] options)
      Main method.
      java.lang.String passwordTipText()
      the tip text for this property
      java.lang.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​(java.lang.String keys)
      Sets the key columns of a database table
      void setOptions​(java.lang.String[] options)
      Sets the options.
      void setPassword​(java.lang.String password)
      Sets user password for the database
      void setQuery​(java.lang.String q)
      Sets the query to execute against the database
      void setSource()
      Sets the database url using the DatabaseUtils file
      void setSource​(java.lang.String url)
      Sets the database url
      void setSource​(java.lang.String url, java.lang.String userName, java.lang.String password)
      Sets the database url, user and pw
      void setUrl​(java.lang.String url)
      Sets the database URL
      void setUser​(java.lang.String user)
      Sets the database user
      java.lang.String urlTipText()
      the tip text for this property
      java.lang.String userTipText()
      the tip text for this property

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • DatabaseLoader

        public DatabaseLoader()
               throws java.lang.Exception
        Constructor
        Throws:
        java.lang.Exception - if initialization fails

    • Method Detail

      • globalInfo

        public java.lang.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 java.lang.Exception
        Resets the Loader ready to read a new data set
        Specified by:
        reset in interface Loader
        Overrides:
        reset in class AbstractLoader
        Throws:
        java.lang.Exception - if an error occurs while disconnecting from the database

      • resetStructure

        public void resetStructure()
        Resets the structure of instances

      • setQuery

        public void setQuery​(java.lang.String q)
        Sets the query to execute against the database
        Parameters:
        q - the query to execute

      • getQuery

        public java.lang.String getQuery()
        Gets the query to execute against the database
        Returns:
        the query

      • queryTipText

        public java.lang.String queryTipText()
        the tip text for this property
        Returns:
        the tip text

      • setKeys

        public void setKeys​(java.lang.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 java.lang.String getKeys()
        Gets the key columns' name
        Returns:
        name of the key columns'

      • keysTipText

        public java.lang.String keysTipText()
        the tip text for this property
        Returns:
        the tip text

      • setUrl

        public void setUrl​(java.lang.String url)
        Sets the database URL
        Specified by:
        setUrl in interface DatabaseConverter
        Parameters:
        url - string with the database URL

      • getUrl

        public java.lang.String getUrl()
        Gets the URL
        Specified by:
        getUrl in interface DatabaseConverter
        Returns:
        the URL

      • urlTipText

        public java.lang.String urlTipText()
        the tip text for this property
        Returns:
        the tip text

      • setUser

        public void setUser​(java.lang.String user)
        Sets the database user
        Specified by:
        setUser in interface DatabaseConverter
        Parameters:
        user - the database user name

      • getUser

        public java.lang.String getUser()
        Gets the user name
        Specified by:
        getUser in interface DatabaseConverter
        Returns:
        name of database user

      • userTipText

        public java.lang.String userTipText()
        the tip text for this property
        Returns:
        the tip text

      • setPassword

        public void setPassword​(java.lang.String password)
        Sets user password for the database
        Specified by:
        setPassword in interface DatabaseConverter
        Parameters:
        password - the password

      • getPassword

        public java.lang.String getPassword()
        Returns the database password
        Returns:
        the database password

      • passwordTipText

        public java.lang.String passwordTipText()
        the tip text for this property
        Returns:
        the tip text

      • setSource

        public void setSource​(java.lang.String url,
                      java.lang.String userName,
                      java.lang.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​(java.lang.String url)
        Sets the database url
        Parameters:
        url - the database url

      • setSource

        public void setSource()
               throws java.lang.Exception
        Sets the database url using the DatabaseUtils file
        Throws:
        java.lang.Exception - if something goes wrong

      • connectToDatabase

        public void connectToDatabase()
        Opens a connection to the database

      • getStructure

        public Instances getStructure()
                       throws java.io.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:
        java.io.IOException - if an error occurs

      • getDataSet

        public Instances getDataSet()
                     throws java.io.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:
        java.io.IOException - if there is no source or parsing fails

      • getNextInstance

        public Instance getNextInstance​(Instances structure)
                         throws java.io.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:
        java.io.IOException - if there is an error during parsing

      • getOptions

        public java.lang.String[] getOptions()
        Gets the setting
        Specified by:
        getOptions in interface OptionHandler
        Returns:
        the current setting

      • listOptions

        public java.util.Enumeration listOptions()
        Lists the available options
        Specified by:
        listOptions in interface OptionHandler
        Returns:
        an enumeration of the available options

      • setOptions

        public void setOptions​(java.lang.String[] options)
                throws java.lang.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:
        java.lang.Exception - if options cannot be set

      • getRevision

        public java.lang.String getRevision()
        Returns the revision string.
        Specified by:
        getRevision in interface RevisionHandler
        Returns:
        the revision

      • main

        public static void main​(java.lang.String[] options)
        Main method.
        Parameters:
        options - the options