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Commit9389ac8

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Document filtering dictionaries in textsearch.sgml.
While at it, copy-edit the description of prefix-match marker support insynonym dictionaries, and clarify the description of the default unaccentdictionary a bit more.
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‎doc/src/sgml/textsearch.sgml‎

Lines changed: 74 additions & 52 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/textsearch.sgml,v 1.58 2010/08/20 13:59:45 tgl Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/textsearch.sgml,v 1.59 2010/08/25 21:42:55 tgl Exp $ -->
22

33
<chapter id="textsearch">
44
<title>Full Text Search</title>
@@ -112,7 +112,7 @@
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as a sorted array of normalized lexemes. Along with the lexemes it is
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often desirable to store positional information to use for
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<firstterm>proximity ranking</firstterm>, so that a document that
115-
contains a more <quote>dense</> region of query words is
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contains a more <quote>dense</> region of query words is
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assigned a higher rank than one with scattered query words.
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</para>
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</listitem>
@@ -1151,13 +1151,13 @@ MaxFragments=0, FragmentDelimiter=" ... "
11511151
<screen>
11521152
SELECT ts_headline('english',
11531153
'The most common type of search
1154-
is to find all documents containing given query terms
1154+
is to find all documents containing given query terms
11551155
and return them in order of their similarity to the
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query.',
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to_tsquery('query &amp; similarity'));
11581158
ts_headline
11591159
------------------------------------------------------------
1160-
containing given &lt;b&gt;query&lt;/b&gt; terms
1160+
containing given &lt;b&gt;query&lt;/b&gt; terms
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and return them in order of their &lt;b&gt;similarity&lt;/b&gt; to the
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&lt;b&gt;query&lt;/b&gt;.
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@@ -1166,7 +1166,7 @@ SELECT ts_headline('english',
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is to find all documents containing given query terms
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and return them in order of their similarity to the
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query.',
1169-
to_tsquery('query &amp; similarity'),
1169+
to_tsquery('query &amp; similarity'),
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'StartSel = &lt;, StopSel = &gt;');
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ts_headline
11721172
-------------------------------------------------------
@@ -2064,6 +2064,14 @@ SELECT alias, description, token FROM ts_debug('http://example.com/stuff/index.h
20642064
(notice that one token can produce more than one lexeme)
20652065
</para>
20662066
</listitem>
2067+
<listitem>
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<para>
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a single lexeme with the <literal>TSL_FILTER</> flag set, to replace
2070+
the original token with a new token to be passed to subsequent
2071+
dictionaries (a dictionary that does this is called a
2072+
<firstterm>filtering dictionary</>)
2073+
</para>
2074+
</listitem>
20672075
<listitem>
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<para>
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an empty array if the dictionary knows the token, but it is a stop word
@@ -2096,6 +2104,13 @@ SELECT alias, description, token FROM ts_debug('http://example.com/stuff/index.h
20962104
until some dictionary recognizes it as a known word. If it is identified
20972105
as a stop word, or if no dictionary recognizes the token, it will be
20982106
discarded and not indexed or searched for.
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Normally, the first dictionary that returns a non-<literal>NULL</>
2108+
output determines the result, and any remaining dictionaries are not
2109+
consulted; but a filtering dictionary can replace the given word
2110+
with a modified word, which is then passed to subsequent dictionaries.
2111+
</para>
2112+
2113+
<para>
20992114
The general rule for configuring a list of dictionaries
21002115
is to place first the most narrow, most specific dictionary, then the more
21012116
general dictionaries, finishing with a very general dictionary, like
@@ -2112,6 +2127,16 @@ ALTER TEXT SEARCH CONFIGURATION astro_en
21122127
</programlisting>
21132128
</para>
21142129

2130+
<para>
2131+
A filtering dictionary can be placed anywhere in the list, except at the
2132+
end where it'd be useless. Filtering dictionaries are useful to partially
2133+
normalize words to simplify the task of later dictionaries. For example,
2134+
a filtering dictionary could be used to remove accents from accented
2135+
letters, as is done by the
2136+
<link linkend="unaccent"><filename>contrib/unaccent</></link>
2137+
extension module.
2138+
</para>
2139+
21152140
<sect2 id="textsearch-stopwords">
21162141
<title>Stop Words</title>
21172142

@@ -2184,7 +2209,7 @@ CREATE TEXT SEARCH DICTIONARY public.simple_dict (
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Here, <literal>english</literal> is the base name of a file of stop words.
21852210
The file's full name will be
21862211
<filename>$SHAREDIR/tsearch_data/english.stop</>,
2187-
where <literal>$SHAREDIR</> means the
2212+
where <literal>$SHAREDIR</> means the
21882213
<productname>PostgreSQL</productname> installation's shared-data directory,
21892214
often <filename>/usr/local/share/postgresql</> (use <command>pg_config
21902215
--sharedir</> to determine it if you're not sure).
@@ -2295,85 +2320,82 @@ SELECT * FROM ts_debug('english', 'Paris');
22952320
asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
22962321
</screen>
22972322
</para>
2298-
2323+
22992324
<para>
2300-
An asterisk (<literal>*</literal>) at the end of definition word indicates
2301-
that definition word is a prefix, and <function>to_tsquery()</function>
2302-
function will transform that definition to the prefix search format (see
2303-
<xref linkend="textsearch-parsing-queries">).
2304-
Notice that it is ignored in <function>to_tsvector()</function>.
2325+
The only parameter required by the <literal>synonym</> template is
2326+
<literal>SYNONYMS</>, which is the base name of its configuration file
2327+
&mdash; <literal>my_synonyms</> in the above example.
2328+
The file's full name will be
2329+
<filename>$SHAREDIR/tsearch_data/my_synonyms.syn</>
2330+
(where <literal>$SHAREDIR</> means the
2331+
<productname>PostgreSQL</> installation's shared-data directory).
2332+
The file format is just one line
2333+
per word to be substituted, with the word followed by its synonym,
2334+
separated by white space. Blank lines and trailing spaces are ignored.
2335+
</para>
2336+
2337+
<para>
2338+
The <literal>synonym</> template also has an optional parameter
2339+
<literal>CaseSensitive</>, which defaults to <literal>false</>. When
2340+
<literal>CaseSensitive</> is <literal>false</>, words in the synonym file
2341+
are folded to lower case, as are input tokens. When it is
2342+
<literal>true</>, words and tokens are not folded to lower case,
2343+
but are compared as-is.
23052344
</para>
23062345

23072346
<para>
2308-
Contents of <filename>$SHAREDIR/tsearch_data/synonym_sample.syn</>:
2347+
An asterisk (<literal>*</literal>) can be placed at the end of a synonym
2348+
in the configuration file. This indicates that the synonym is a prefix.
2349+
The asterisk is ignored when the entry is used in
2350+
<function>to_tsvector()</function>, but when it is used in
2351+
<function>to_tsquery()</function>, the result will be a query item with
2352+
the prefix match marker (see
2353+
<xref linkend="textsearch-parsing-queries">).
2354+
For example, suppose we have these entries in
2355+
<filename>$SHAREDIR/tsearch_data/synonym_sample.syn</>:
23092356
<programlisting>
23102357
postgres pgsql
23112358
postgresql pgsql
23122359
postgre pgsql
23132360
gogle googl
23142361
indices index*
23152362
</programlisting>
2316-
</para>
2317-
2318-
<para>
2319-
Results:
2363+
Then we will get these results:
23202364
<screen>
2321-
=# CREATE TEXT SEARCH DICTIONARY syn (template=synonym, synonyms='synonym_sample');
2322-
=# SELECT ts_lexize('syn','indices');
2365+
mydb=# CREATE TEXT SEARCH DICTIONARY syn (template=synonym, synonyms='synonym_sample');
2366+
mydb=# SELECT ts_lexize('syn','indices');
23232367
ts_lexize
23242368
-----------
23252369
{index}
23262370
(1 row)
23272371

2328-
=# CREATE TEXT SEARCH CONFIGURATION tst (copy=simple);
2329-
=# ALTER TEXT SEARCH CONFIGURATION tst ALTER MAPPING FOR asciiword WITH syn;
2330-
=# SELECT to_tsquery('tst','indices');
2372+
mydb=# CREATE TEXT SEARCH CONFIGURATION tst (copy=simple);
2373+
mydb=# ALTER TEXT SEARCH CONFIGURATION tst ALTER MAPPING FOR asciiword WITH syn;
2374+
mydb=# SELECT to_tsvector('tst','indices');
2375+
to_tsvector
2376+
-------------
2377+
'index':1
2378+
(1 row)
2379+
2380+
mydb=# SELECT to_tsquery('tst','indices');
23312381
to_tsquery
23322382
------------
23332383
'index':*
23342384
(1 row)
23352385

2336-
=# SELECT 'indexes are very useful'::tsvector;
2386+
mydb=# SELECT 'indexes are very useful'::tsvector;
23372387
tsvector
23382388
---------------------------------
23392389
'are' 'indexes' 'useful' 'very'
23402390
(1 row)
23412391

2342-
=# SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices');
2392+
mydb=# SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices');
23432393
?column?
23442394
----------
23452395
t
23462396
(1 row)
2347-
2348-
=# SELECT to_tsvector('tst','indices');
2349-
to_tsvector
2350-
-------------
2351-
'index':1
2352-
(1 row)
23532397
</screen>
23542398
</para>
2355-
2356-
<para>
2357-
The only parameter required by the <literal>synonym</> template is
2358-
<literal>SYNONYMS</>, which is the base name of its configuration file
2359-
&mdash; <literal>my_synonyms</> in the above example.
2360-
The file's full name will be
2361-
<filename>$SHAREDIR/tsearch_data/my_synonyms.syn</>
2362-
(where <literal>$SHAREDIR</> means the
2363-
<productname>PostgreSQL</> installation's shared-data directory).
2364-
The file format is just one line
2365-
per word to be substituted, with the word followed by its synonym,
2366-
separated by white space. Blank lines and trailing spaces are ignored.
2367-
</para>
2368-
2369-
<para>
2370-
The <literal>synonym</> template also has an optional parameter
2371-
<literal>CaseSensitive</>, which defaults to <literal>false</>. When
2372-
<literal>CaseSensitive</> is <literal>false</>, words in the synonym file
2373-
are folded to lower case, as are input tokens. When it is
2374-
<literal>true</>, words and tokens are not folded to lower case,
2375-
but are compared as-is.
2376-
</para>
23772399
</sect2>
23782400

23792401
<sect2 id="textsearch-thesaurus">

‎doc/src/sgml/unaccent.sgml‎

Lines changed: 5 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $PostgreSQL: pgsql/doc/src/sgml/unaccent.sgml,v 1.6 2010/08/2502:12:00 tgl Exp $ -->
1+
<!-- $PostgreSQL: pgsql/doc/src/sgml/unaccent.sgml,v 1.7 2010/08/2521:42:55 tgl Exp $ -->
22

33
<sect1 id="unaccent">
44
<title>unaccent</title>
@@ -75,8 +75,10 @@
7575
<para>
7676
Running the installation script <filename>unaccent.sql</> creates a text
7777
search template <literal>unaccent</> and a dictionary <literal>unaccent</>
78-
based on it, with default parameters. You can alter the
79-
parameters, for example
78+
based on it. The <literal>unaccent</> dictionary has the default
79+
parameter setting <literal>RULES='unaccent'</>, which makes it immediately
80+
usable with the standard <filename>unaccent.rules</> file.
81+
If you wish, you can alter the parameter, for example
8082

8183
<programlisting>
8284
mydb=# ALTER TEXT SEARCH DICTIONARY unaccent (RULES='my_rules');

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