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Updated on 2024-09-03 GMT+08:00
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Synonym Dictionary

A synonym dictionary is used to define, identify, and convert synonyms of tokens. Phrases are not supported (use the thesaurus dictionary in Thesaurus Dictionary).

Examples

  • A synonym dictionary can be used to overcome linguistic problems, for example, to prevent an English stemmer dictionary from reducing the word "Paris" to "pari". It is enough to have a Paris paris line in the synonym dictionary and put it before the english_stem dictionary. 
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    SELECT * FROM ts_debug('english', 'Paris');


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    CREATE TEXT SEARCH DICTIONARY my_synonym (
    TEMPLATE = synonym,
    SYNONYMS = my_synonyms,
    FILEPATH =   'obs://bucket01/obs.example.com accesskey=xxxxx secretkey=xxxxx region=ap-southeast-1'
);

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

SELECT * FROM ts_debug('english', 'Paris');


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    SELECT * FROM ts_debug('english', 'paris');


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    ALTER TEXT SEARCH DICTIONARY my_synonym ( CASESENSITIVE=true);


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    SELECT * FROM ts_debug('english', 'paris');

    The full name of the synonym dictionary file is my_synonyms.syn, and the dictionary is stored in 'obs://bucket01/obs.example.com accesskey=xxxxx secretkey=xxxxx region=ap-southeast-1'. For details about the syntax and parameters for creating a synonym dictionary, see CREATE TEXT SEARCH DICTIONARY.

  • An asterisk (*) can be placed at the end of a synonym in the configuration file. This indicates that the synonym is a prefix. The asterisk is ignored when the entry is used in to_tsvector(), but when it is used in to_tsquery(), the result will be a query item with the prefix match marker (see Manipulating Queries).

    Assume that the content in the dictionary file synonym_sample.syn is as follows:

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    postgres        pgsql
postgresql      pgsql 
postgre pgsql 
gogle   googl 
indices index*

    Create and use a dictionary.

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

SELECT ts_lexize('syn','indices');


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    CREATE TEXT SEARCH CONFIGURATION tst (copy=simple);

ALTER TEXT SEARCH CONFIGURATION tst ALTER MAPPING FOR asciiword WITH syn;

SELECT to_tsvector('tst','indices');


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    SELECT to_tsquery('tst','indices');


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    SELECT 'indexes are very useful'::tsvector;


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    SELECT 'indexes are very useful'::tsvector @@ to_tsquery('tst','indices');

Parent topic: Dictionaries