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。

    1. openGauss=# SELECT * FROM ts_debug('english', 'Paris');
    2.    alias   |   description   | token |  dictionaries  |  dictionary  | lexemes 
    3. -----------+-----------------+-------+----------------+--------------+---------
    4.  asciiword | Word, all ASCII | Paris | {english_stem} | english_stem | {pari}
    5. (1 row)
    7. openGauss=# CREATE TEXT SEARCH DICTIONARY my_synonym (
    8.     TEMPLATE = synonym,
    9.     SYNONYMS = my_synonyms,
    10.     FILEPATH = 'file:///home/dicts/' 
    11. );
    13. openGauss=# ALTER TEXT SEARCH CONFIGURATION english
    14.     ALTER MAPPING FOR asciiword
    15.     WITH my_synonym, english_stem;
    17. openGauss=# SELECT * FROM ts_debug('english', 'Paris');
    18.    alias   |   description   | token |       dictionaries        | dictionary | lexemes 
    19. -----------+-----------------+-------+---------------------------+------------+---------
    20.  asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
    21. (1 row)
    23. openGauss=# SELECT * FROM ts_debug('english', 'paris');
    24.    alias   |   description   | token |       dictionaries        | dictionary | lexemes 
    25. -----------+-----------------+-------+---------------------------+------------+---------
    26.  asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
    27. (1 row)
    29. openGauss=# ALTER TEXT SEARCH DICTIONARY my_synonym ( CASESENSITIVE=true);
    31. openGauss=# SELECT * FROM ts_debug('english', 'Paris');
    32.    alias   |   description   | token |       dictionaries        | dictionary | lexemes 
    33. -----------+-----------------+-------+---------------------------+------------+---------
    34.  asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}
    35. (1 row)
    37. openGauss=# SELECT * FROM ts_debug('english', 'paris');
    38.    alias   |   description   | token |       dictionaries        | dictionary | lexemes 
    39. -----------+-----------------+-------+---------------------------+------------+---------
    40.  asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {pari}
    41. (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：

    1. postgres        pgsql
    2. postgresql      pgsql 
    3. postgre pgsql 
    4. gogle   googl 
    5. indices index*

    创建并使用词典：

    1. openGauss=# CREATE TEXT SEARCH DICTIONARY syn (
    2.     TEMPLATE = synonym,
    3.     SYNONYMS = synonym_sample
    4. );
    6. openGauss=# SELECT ts_lexize('syn','indices');
    7.  ts_lexize 
    8. -----------
    9.  {index}
    10. (1 row)
    12. openGauss=# CREATE TEXT SEARCH CONFIGURATION tst (copy=simple);
    14. openGauss=# ALTER TEXT SEARCH CONFIGURATION tst ALTER MAPPING FOR asciiword WITH syn;
    16. openGauss=# SELECT to_tsvector('tst','indices');
    17.  to_tsvector 
    18. -------------
    19.  'index':1
    20. (1 row)
    22. openGauss=# SELECT to_tsquery('tst','indices');
    23.  to_tsquery 
    24. ------------
    25.  'index':*
    26. (1 row)
    28. openGauss=# SELECT 'indexes are very useful'::tsvector;
    29.             tsvector             
    30. ---------------------------------
    31.  'are' 'indexes' 'useful' 'very'
    32. (1 row)
    34. openGauss=# SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices');
    35.  ?column? 
    36. ----------
    37.  t
    38. (1 row)