---
title: "dict_xsyn — example synonym full-text search dictionary"
id: dict-xsyn
pg_version: "20devel"
---

<a id="dict-xsyn"></a>

## F.13. dict_xsyn — example synonym full-text search dictionary

`dict_xsyn` (Extended Synonym Dictionary) is an example of an add-on dictionary template for full-text search. This dictionary type replaces words with groups of their synonyms, and so makes it possible to search for a word using any of its synonyms. 

<a id="dict-xsyn-config"></a>

### F.13.1. Configuration

A `dict_xsyn` dictionary accepts the following options: 


-  `matchorig` controls whether the original word is accepted by the dictionary. Default is `true`. 
-  `matchsynonyms` controls whether the synonyms are accepted by the dictionary. Default is `false`. 
-  `keeporig` controls whether the original word is included in the dictionary's output. Default is `true`. 
-  `keepsynonyms` controls whether the synonyms are included in the dictionary's output. Default is `true`. 
-  `rules` is the base name of the file containing the list of synonyms. This file must be stored in `$SHAREDIR/tsearch_data/` (where `$SHAREDIR` means the PostgreSQL installation's shared-data directory). Its name must end in `.rules` (which is not to be included in the `rules` parameter). 

The rules file has the following format: 


-  Each line represents a group of synonyms for a single word, which is given first on the line. Synonyms are separated by whitespace, thus: 
word syn1 syn2 syn3
 
-  The sharp (`#`) sign is a comment delimiter. It may appear at any position in a line. The rest of the line will be skipped. 

Look at `xsyn_sample.rules`, which is installed in `$SHAREDIR/tsearch_data/`, for an example. 

<a id="dict-xsyn-usage"></a>

### F.13.2. Usage

Installing the `dict_xsyn` extension creates a text search template `xsyn_template` and a dictionary `xsyn` based on it, with default parameters. You can alter the parameters, for example 
mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=false);
ALTER TEXT SEARCH DICTIONARY
 or create new dictionaries based on the template. 

To test the dictionary, you can try 
mydb=# SELECT ts_lexize('xsyn', 'word');
      ts_lexize
-----------------------
 {syn1,syn2,syn3}

mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=true);
ALTER TEXT SEARCH DICTIONARY

mydb=# SELECT ts_lexize('xsyn', 'word');
      ts_lexize
-----------------------
 {word,syn1,syn2,syn3}

mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=false, MATCHSYNONYMS=true);
ALTER TEXT SEARCH DICTIONARY

mydb=# SELECT ts_lexize('xsyn', 'syn1');
      ts_lexize
-----------------------
 {syn1,syn2,syn3}

mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=true, MATCHORIG=false, KEEPSYNONYMS=false);
ALTER TEXT SEARCH DICTIONARY

mydb=# SELECT ts_lexize('xsyn', 'syn1');
      ts_lexize
-----------------------
 {word}
 Real-world usage will involve including it in a text search configuration as described in [Chapter 12](textsearch.md). That might look like this: 
ALTER TEXT SEARCH CONFIGURATION english
    ALTER MAPPING FOR word, asciiword WITH xsyn, english_stem;