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)

1. openGauss=# CREATE TEXT SEARCH DICTIONARY my_synonym (
2. TEMPLATE = synonym,
3. SYNONYMS = my_synonyms,
4. FILEPATH = 'file:///home/dicts/'

5. );

6. openGauss=# ALTER TEXT SEARCH CONFIGURATION english

7. ALTER MAPPING FOR asciiword

8. WITH my_synonym, english_stem;

9. openGauss=# SELECT * FROM ts_debug('english', 'Paris');

10. alias | description | token | dictionaries | dictionary | lexemes
11. -----------+-----------------+-------+---------------------------+------------+---------
12. asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}

13. (1 row)

14. openGauss=# SELECT * FROM ts_debug('english', 'paris');

15. alias | description | token | dictionaries | dictionary | lexemes
16. -----------+-----------------+-------+---------------------------+------------+---------
17. asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}

18. (1 row)

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

20. openGauss=# SELECT * FROM ts_debug('english', 'Paris');

21. alias | description | token | dictionaries | dictionary | lexemes
22. -----------+-----------------+-------+---------------------------+------------+---------
23. asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {paris}

24. (1 row)

25. openGauss=# SELECT * FROM ts_debug('english', 'paris');

26. alias | description | token | dictionaries | dictionary | lexemes
27. -----------+-----------------+-------+---------------------------+------------+---------
28. asciiword | Word, all ASCII | Paris | {my_synonym,english_stem} | my_synonym | {pari}
29. (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. );

1. openGauss=# SELECT ts_lexize('syn','indices');
2. ts_lexize

3. ---

4. {index}

5. (1 row)

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

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

8. openGauss=# SELECT to_tsvector('tst','indices');

9. to_tsvector

10. ---

11. 'index':1

12. (1 row)

13. openGauss=# SELECT to_tsquery('tst','indices');

14. to_tsquery

15. ---

16. 'index':*

17. (1 row)

18. openGauss=# SELECT 'indexes are very useful'::tsvector;

19. tsvector

20. ---

21. 'are' 'indexes' 'useful' 'very'

22. (1 row)

23. openGauss=# SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices');

24. ?column?

25. ---

26. t
27. (1 row) ```