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更新时间：2023-10-23 GMT+08:00
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Synonym词典

Synonym词典用于定义、识别token的同义词并转化，不支持词组（词组形式的同义词可用Thesaurus词典定义，详细请参见Thesaurus词典）。

示例

  • Synonym词典可用于解决语言学相关问题，例如，为避免使单词"Paris"变成"pari"，可在Synonym词典文件中定义一行"Paris paris"，并将该词典放置在预定义的english_stem词典之前。 
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    openGauss=# SELECT * FROM ts_debug('english', 'Paris');
   alias   |   description   | token |  dictionaries  |  dictionary  | lexemes 
-----------+-----------------+-------+----------------+--------------+---------
 asciiword | Word, all ASCII | Paris | {english_stem} | english_stem | {pari}
(1 row)

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

openGauss=# ALTER TEXT SEARCH CONFIGURATION english
    ALTER MAPPING FOR asciiword
    WITH my_synonym, english_stem;

openGauss=# SELECT * FROM ts_debug('english', 'Paris');
   alias   |   description   | token |       dictionaries        | dictionary | lexemes 
-----------+-----------------+-------+---------------------------+------------+---------
 asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
(1 row)

openGauss=# SELECT * FROM ts_debug('english', 'paris');
   alias   |   description   | token |       dictionaries        | dictionary | lexemes 
-----------+-----------------+-------+---------------------------+------------+---------
 asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
(1 row)

openGauss=# ALTER TEXT SEARCH DICTIONARY my_synonym ( CASESENSITIVE=true);

openGauss=# SELECT * FROM ts_debug('english', 'Paris');
   alias   |   description   | token |       dictionaries        | dictionary | lexemes 
-----------+-----------------+-------+---------------------------+------------+---------
 asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
(1 row)

openGauss=# SELECT * FROM ts_debug('english', 'paris');
   alias   |   description   | token |       dictionaries        | dictionary | lexemes 
-----------+-----------------+-------+---------------------------+------------+---------
 asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {pari}
(1 row)

    其中，同义词词典文件全名为my_synonyms.syn，所在目录为当前连接数据库主节点的/home/dicts/下。关于创建词典的语法和更多参数，请参见ALTER TEXT SEARCH DICTIONARY。

  • 星号（*）可用于词典文件中的同义词结尾，表示该同义词是一个前缀。在to_tsvector()中该星号将被忽略，但在to_tsquery()中会匹配该前缀并对应输出结果（参照处理查询一节）。

    假设词典文件synonym_sample.syn内容如下：

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    postgres        pgsql
postgresql      pgsql 
postgre pgsql 
gogle   googl 
indices index*

    创建并使用词典：

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    openGauss=# CREATE TEXT SEARCH DICTIONARY syn (
    TEMPLATE = synonym,
    SYNONYMS = synonym_sample
);

openGauss=# SELECT ts_lexize('syn','indices');
 ts_lexize 
-----------
 {index}
(1 row)

openGauss=# CREATE TEXT SEARCH CONFIGURATION tst (copy=simple);

openGauss=# ALTER TEXT SEARCH CONFIGURATION tst ALTER MAPPING FOR asciiword WITH syn;

openGauss=# SELECT to_tsvector('tst','indices');
 to_tsvector 
-------------
 'index':1
(1 row)

openGauss=# SELECT to_tsquery('tst','indices');
 to_tsquery 
------------
 'index':*
(1 row)

openGauss=# SELECT 'indexes are very useful'::tsvector;
            tsvector             
---------------------------------
 'are' 'indexes' 'useful' 'very'
(1 row)

openGauss=# SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices');
 ?column? 
----------
 t
(1 row)
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