# 12.7. 組態範例

A text search configuration specifies all options necessary to transform a document into a`tsvector`: the parser to use to break text into tokens, and the dictionaries to use to transform each token into a lexeme. Every call of`to_tsvector`or`to_tsquery`needs a text search configuration to perform its processing. The configuration parameter[default\_text\_search\_config](https://www.postgresql.org/docs/10/static/runtime-config-client.html#guc-default-text-search-config)specifies the name of the default configuration, which is the one used by text search functions if an explicit configuration parameter is omitted. It can be set in`postgresql.conf`, or set for an individual session using the`SET`command.

Several predefined text search configurations are available, and you can create custom configurations easily. To facilitate management of text search objects, a set ofSQLcommands is available, and there are severalpsqlcommands that display information about text search objects ([Section 12.10](https://www.postgresql.org/docs/10/static/textsearch-psql.html)).

As an example we will create a configuration`pg`, starting by duplicating the built-in`english`configuration:

```
CREATE TEXT SEARCH CONFIGURATION public.pg ( COPY = pg_catalog.english );
```

We will use a PostgreSQL-specific synonym list and store it in`$SHAREDIR/tsearch_data/pg_dict.syn`. The file contents look like:

```
postgres    pg
pgsql       pg
postgresql  pg
```

We define the synonym dictionary like this:

```
CREATE TEXT SEARCH DICTIONARY pg_dict (
    TEMPLATE = synonym,
    SYNONYMS = pg_dict
);
```

Next we register theIspelldictionary`english_ispell`, which has its own configuration files:

```
CREATE TEXT SEARCH DICTIONARY english_ispell (
    TEMPLATE = ispell,
    DictFile = english,
    AffFile = english,
    StopWords = english
);
```

Now we can set up the mappings for words in configuration`pg`:

```
ALTER TEXT SEARCH CONFIGURATION pg
    ALTER MAPPING FOR asciiword, asciihword, hword_asciipart,
                      word, hword, hword_part
    WITH pg_dict, english_ispell, english_stem;
```

We choose not to index or search some token types that the built-in configuration does handle:

```
ALTER TEXT SEARCH CONFIGURATION pg
    DROP MAPPING FOR email, url, url_path, sfloat, float;
```

Now we can test our configuration:

```
SELECT * FROM ts_debug('public.pg', '
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.
');
```

The next step is to set the session to use the new configuration, which was created in the`public`schema:

```
=
>
 \dF
   List of text search configurations
 Schema  | Name | Description
---------+------+-------------
 public  | pg   |

SET default_text_search_config = 'public.pg';
SET

SHOW default_text_search_config;
 default_text_search_config
----------------------------
 public.pg
```


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