4.4 Using Stopwords and Stoplists

A stopword is a word that is not to be indexed, such as this or that in English.

The system supplies a stoplist for every language. By default during indexing, the system uses the Oracle Text default stoplist for your language.

You can edit the default CTXSYS.DEFAULT_STOPLIST or create your own with the following PL/SQL procedures:

  • CTX_DDL.CREATE_STOPLIST

  • CTX_DDL.ADD_STOPWORD

  • CTX_DDL.REMOVE_STOPWORD

You specify your custom stoplists in the parameter clause of CREATE INDEX.

You can also dynamically add stopwords after indexing with the ALTER INDEX statement.

4.4.1 Multilanguage Stoplists

You can create multilanguage stoplists to hold language-specific stopwords. This stoplist is useful when you use MULTI_LEXER to index a table that contains documents in different languages, such as English, German, and Japanese.

To create a multilanguage stoplist, use the CTX_DDL.CREATE_STOPLIST procedure and specify a stoplist type of MULTI_STOPLIST. You add language-specific stopwords with CTX_DDL.ADD_STOPWORD.

4.4.2 Stopthemes and Stopclasses

In addition to defining your own stopwords, you can define stopthemes, which are themes that are not indexed. This feature is available only for English and French.

You can also specify that numbers are not indexed. A class of alphanumeric characters such a numbers that is not to be indexed is a stopclass.

You create a single stoplist, to which you add the stopwords, stopthemes, and stopclasses, and specify the stoplist in the paramstring for CREATE INDEX.

4.4.3 PL/SQL Procedures for Managing Stoplists

Use the following procedures to manage stoplists, stopwords, stopthemes, and stopclasses:

  • CTX_DDL.CREATE_STOPLIST

  • CTX_DDL.ADD_STOPWORD

  • CTX_DDL.ADD_STOPTHEME

  • CTX_DDL.ADD_STOPCLASS

  • CTX_DDL.REMOVE_STOPWORD

  • CTX_DDL.REMOVE_STOPTHEME

  • CTX_DDL.REMOVE_STOPCLASS

  • CTX_DDL.DROP_STOPLIST

    See Also:

    Oracle Text Reference to learn more about using these procedures