华为openGauss 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。

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

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

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

  postgres=# 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)

  postgres=# 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)

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

  postgres=# 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)

  postgres=# 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CREATE 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：

  postgres pgsql postgresql pgsql postgre pgsql gogle googl indices index*

  创建并使用词典：

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

  postgres=# SELECT ts_lexize('syn','indices'); ts_lexize

  ---

  {index} (1 row)

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

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

  postgres=# SELECT to_tsvector('tst','indices'); to_tsvector

  ---

  'index':1 (1 row)

  postgres=# SELECT to_tsquery('tst','indices'); to_tsquery

  ---

  'index':* (1 row)

  postgres=# SELECT 'indexes are very useful'::tsvector; tsvector

  ---

  'are' 'indexes' 'useful' 'very' (1 row)

  postgres=# SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices'); ?column?

  ---

  t (1 row) ```