Page History

In OracleText, the full-text index is case insensitive by default. The case-sensitivity of the index can be specified at creation time or changed later using lexer preferences.

Creating a case-insensitive lexer

To enable case-sensitivity, a custom lexer must be defined and configured:

begin
	ctx_ddl.create_preference('example_lexer', 'BASIC_LEXER');
	ctx_ddl.set_attribute('example_lexer', 'mixed_case', 'no'); -- no = case sensitive, yes = case insensitive
end;

Setting the lexer at index creation time

The custom lexer is specified as an index parameter:

drop index aq_fulltext_index;
create index aq_fulltext_index on aq_fulltext(text) 
  indextype is ctxsys.context 
  parameters ('datastore aq_fulltext_uds lexer example_lexer sync(every "sysdate+1/24")');

Changing the lexer without recreating the index

The lexer can also be changed without dropping the index first:

...

• the 'alter index rebuild parameters' may not be used to change the lexer, instead changing the lexer and rebuilding the index must be done using two separate statements
• simply changing the value of an attribute on a lexer preference has no effect on the full-text index, the 'alter index parameters' statement must be used
• after the lexer is changed, the effects will not become visible until the index is rebuilt

...

...

...