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><A
NAME="TEXTSEARCH-CONFIGURATION"
>12.7. Configuration Example</A
></H1
><P
> A text search configuration specifies all options necessary to transform a
document into a <TT
CLASS="TYPE"
>tsvector</TT
>: the parser to use to break text
into tokens, and the dictionaries to use to transform each token into a
lexeme. Every call of
<CODE
CLASS="FUNCTION"
>to_tsvector</CODE
> or <CODE
CLASS="FUNCTION"
>to_tsquery</CODE
>
needs a text search configuration to perform its processing.
The configuration parameter
<A
HREF="runtime-config-client.html#GUC-DEFAULT-TEXT-SEARCH-CONFIG"
>default_text_search_config</A
>
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 <TT
CLASS="FILENAME"
>postgresql.conf</TT
>, or set for an
individual session using the <TT
CLASS="COMMAND"
>SET</TT
> command.
</P
><P
> Several predefined text search configurations are available, and
you can create custom configurations easily. To facilitate management
of text search objects, a set of <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
> commands
is available, and there are several <SPAN
CLASS="APPLICATION"
>psql</SPAN
> commands that display information
about text search objects (<A
HREF="textsearch-psql.html"
>Section 12.10</A
>).
</P
><P
> As an example, we will create a configuration
<TT
CLASS="LITERAL"
>pg</TT
>, starting from a duplicate of the built-in
<TT
CLASS="LITERAL"
>english</TT
> configuration.
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE TEXT SEARCH CONFIGURATION public.pg ( COPY = pg_catalog.english );</PRE
><P>
</P
><P
> We will use a PostgreSQL-specific synonym list
and store it in <TT
CLASS="FILENAME"
>$SHAREDIR/tsearch_data/pg_dict.syn</TT
>.
The file contents look like:
</P><PRE
CLASS="PROGRAMLISTING"
>postgres pg
pgsql pg
postgresql pg</PRE
><P>
We define the synonym dictionary like this:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE TEXT SEARCH DICTIONARY pg_dict (
TEMPLATE = synonym,
SYNONYMS = pg_dict
);</PRE
><P>
Next we register the <SPAN
CLASS="PRODUCTNAME"
>Ispell</SPAN
> dictionary
<TT
CLASS="LITERAL"
>english_ispell</TT
>, which has its own configuration files:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE TEXT SEARCH DICTIONARY english_ispell (
TEMPLATE = ispell,
DictFile = english,
AffFile = english,
StopWords = english
);</PRE
><P>
Now we can set up the mappings for words in configuration
<TT
CLASS="LITERAL"
>pg</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>ALTER TEXT SEARCH CONFIGURATION pg
ALTER MAPPING FOR asciiword, asciihword, hword_asciipart,
word, hword, hword_part
WITH pg_dict, english_ispell, english_stem;</PRE
><P>
We choose not to index or search some token types that the built-in
configuration does handle:
</P><PRE
CLASS="PROGRAMLISTING"
>ALTER TEXT SEARCH CONFIGURATION pg
DROP MAPPING FOR email, url, url_path, sfloat, float;</PRE
><P>
</P
><P
> Now we can test our configuration:
</P><PRE
CLASS="PROGRAMLISTING"
>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.
');</PRE
><P>
</P
><P
> The next step is to set the session to use the new configuration, which was
created in the <TT
CLASS="LITERAL"
>public</TT
> schema:
</P><PRE
CLASS="PROGRAMLISTING"
>=> \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</PRE
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distrib
>
Mandriva
>
2008.1
>
x86_64
>
media
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>
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