Configuration Examples

Text search configuration specifies the following components required for converting a document into a tsvector:

• A parser, decomposes a text into tokens.
• Dictionary list, converts each token into a lexeme.

Each time when the to_tsvector or to_tsquery function is invoked, a text search configuration is required to specify a processing procedure. The GUC parameter default_text_search_config specifies the default text search configuration, which will be used if the text search function does not explicitly specify a text search configuration.

MogDB provides some predefined text search configurations. You can also create user-defined text search configurations. In addition, to facilitate the management of text search objects, multiple gsql meta-commands are provided to display information about text search objects. For details, see "Client Tool > Meta-Command Reference" in Tool Reference.

Procedure

1. Create a text search configuration ts_conf by copying the predefined text search configuration english.

   MogDB=# CREATE TEXT SEARCH CONFIGURATION ts_conf ( COPY = pg_catalog.english );
   CREATE TEXT SEARCH CONFIGURATION

2. Create a Synonym dictionary.

   Assume that the definition file pg_dict.syn of the Synonym dictionary contains the following contents:

   postgres    pg
   pgsql       pg
   postgresql  pg

   Run the following statement to create the Synonym dictionary:

   MogDB=# CREATE TEXT SEARCH DICTIONARY pg_dict (
        TEMPLATE = synonym,
        SYNONYMS = pg_dict,
        FILEPATH = 'file:///home/dicts'
    );

3. Create an Ispell dictionary english_ispell (the dictionary definition file is from the open source dictionary).

   MogDB=# CREATE TEXT SEARCH DICTIONARY english_ispell (
       TEMPLATE = ispell,
       DictFile = english,
       AffFile = english,
       StopWords = english,
       FILEPATH = 'file:///home/dicts'
   );

4. Modify the text search configuration ts_conf and change the dictionary list for tokens of certain types. For details about token types, see Parser.

   MogDB=# ALTER TEXT SEARCH CONFIGURATION ts_conf
       ALTER MAPPING FOR asciiword, asciihword, hword_asciipart,
                         word, hword, hword_part
       WITH pg_dict, english_ispell, english_stem;

5. In the text search configuration, set non-index or set the search for tokens of certain types.

   MogDB=# ALTER TEXT SEARCH CONFIGURATION ts_conf
       DROP MAPPING FOR email, url, url_path, sfloat, float;

6. Use the text retrieval commissioning function ts_debug() to test the text search configuration ts_conf.

   MogDB=# SELECT * FROM ts_debug('ts_conf', '
   PostgreSQL, the highly scalable, SQL compliant, open source object-relational
   database management system, is now undergoing beta testing of the next
   version of our software.
   ');

7. You can set the default text search configuration of the current session to ts_conf. This setting is valid only for the current session.

   MogDB=# \dF+ ts_conf
         Text search configuration "public.ts_conf"
   Parser: "pg_catalog.default"
         Token      |            Dictionaries
   -----------------+-------------------------------------
    asciihword      | pg_dict,english_ispell,english_stem
    asciiword       | pg_dict,english_ispell,english_stem
    file            | simple
    host            | simple
    hword           | pg_dict,english_ispell,english_stem
    hword_asciipart | pg_dict,english_ispell,english_stem
    hword_numpart   | simple
    hword_part      | pg_dict,english_ispell,english_stem
    int             | simple
    numhword        | simple
    numword         | simple
    uint            | simple
    version         | simple
    word            | pg_dict,english_ispell,english_stem
   
   MogDB=# SET default_text_search_config = 'public.ts_conf';
   SET
   MogDB=# SHOW default_text_search_config;
    default_text_search_config
   ----------------------------
    public.ts_conf
   (1 row)