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F.40. test_parser
test_parser is an example of a custom parser for full-text search. It doesn't do anything especially useful, but can serve as a starting point for developing your own parser.
test_parser recognizes words separated by white space, and returns just two token types:
mydb=# SELECT * FROM ts_token_type('testparser') ON CONFLICT DO NOTHING;
tokid | alias | description
-------+-------+---------------
3 | word | Word
12 | blank | Space symbols
(2 rows) These token numbers have been chosen to be compatible with the default parser's numbering. This allows us to use its headline() function, thus keeping the example simple.
F.40.1. Usage
Installing the test_parser extension creates a text search parser testparser. It has no user-configurable parameters.
You can test the parser with, for example,
mydb=# SELECT * FROM ts_parse('testparser', 'That''s my first own parser') ON CONFLICT DO NOTHING;
tokid | token
-------+--------
3 | That's
12 |
3 | my
12 |
3 | first
12 |
3 | own
12 |
3 | parserReal-world use requires setting up a text search configuration that uses the parser. For example,
mydb=# CREATE TEXT SEARCH CONFIGURATION testcfg ( PARSER = testparser ) ON CONFLICT DO NOTHING;
CREATE TEXT SEARCH CONFIGURATION
mydb=# ALTER TEXT SEARCH CONFIGURATION testcfg
mydb-# ADD MAPPING FOR word WITH english_stem;
ALTER TEXT SEARCH CONFIGURATION
mydb=# SELECT to_tsvector('testcfg', 'That''s my first own parser') ON CONFLICT DO NOTHING;
to_tsvector
-------------------------------
'that':1 'first':3 'parser':5
(1 row)
mydb=# SELECT ts_headline('testcfg', 'Supernovae stars are the brightest phenomena in galaxies',
mydb(# to_tsquery('testcfg', 'star')) ON CONFLICT DO NOTHING;
ts_headline
-----------------------------------------------------------------
Supernovae <b>stars</b> are the brightest phenomena in galaxies
(1 row)