Postgres CJK Parser pg_cjk_parser is a fts (full text search) parser derived from the default parser in PostgreSQL. When a postgres database uses utf-8 encoding, this parser supports all the features of the default parser while splitting CJK (Chinese, Japanese, Korean) characters into 2-gram tokens. If the database's encoding is not utf-8, the parser behaves just like the default parser.

Now pg_cjk_parser supports PostgreSQL 12 to 16.

It is not easy for text search parsers to split strings with CJK charatcters into words because in CJK languages, space is not word boundary. PostgreSQL's default parser treats CJK characters as a single word "Word, all letters". This is undesirable for CJK users.

The pg_cjk_parser extends the default parser by splitting CJK into 2-gram tokens while splitting other languages the way the default parser does.

Please note that CJK punctuations are treated as unigram and will not be part of any 2-gram CJK tokens.

SELECT alias, description, token FROM 
ts_debug('Doraemnon Nobita「ドラえもん のび太の牧場物語」多拉A梦 野比大雄χΨψΩω https://www.doraemon.com/welcome.html');

You can build pg_cjk_parser in a docker container.

1. Clone this repository into your local computer, say in /home/user/pg_cjk_parser
2. Ener /home/user/pg_cjk_parser
3. Build the docker image postgres:12-dev

To build this extension for PostgreSQL 12

docker build -t postgres:12-dev . --build-arg POSTGRES_VERSION=12 -f Dockerfile_alpine

To build this extension for PostgreSQL 16

docker build -t postgres:16-dev . --build-arg POSTGRES_VERSION=16 -f Dockerfile_alpine

To build this extension for PostgreSQL 11

docker build -t postgres:11-dev . -f Dockerfile_pg11

4. Run the following command

docker run -it --rm -v $(pwd):/root/code postgres:12-dev /bin/bash -c "cd /root/code && make clean && make"

Then pg_cjk_parser.bc and pg_cjk_parser.so will be available in current directory (/home/user/pg_cjk_parser). You can manually install the parser to a PostgreSQL instances or you can install it as an extension.

You can manually install pg_cjk_parser or you can install it as an extension.

Let's say that you have an instance of PostgreSQL 12 running, either on a docker container on a server. Make sure you have the following dependencies installed.

# replace 12 with 16 if you build this extension for pg 16
sudo apt-get install -y postgresql-server-dev-12 
sudo apt-get install -y gcc
sudo apt-get install -y icu-devtools libicu-dev

If you are using other Linux distrubitions other than debian or ubuntu, you should replace "apt-get install -y" with corresponding commands.

Copy the following files

pg_cjk_parser.c pg_cjk_parser.control pg_cjk_parser--0.0.1.sql zht2zhs.h Makefile

to a directory on the server, say, /home/user/parser/

Run the following command on the server

cd /home/user/parser
make clean && make install
sudo make USE_PGXS=1 install

Connect to your server via pgAdmin or other clients and then execute the following sql to create the pg_cjk_parser extension.

CREATE EXTENSION pg_cjk_parser;

Then you should create a search configuration and make it default.

CREATE TEXT SEARCH PARSER public.pg_cjk_parser (
    START = prsd2_cjk_start,
    GETTOKEN = prsd2_cjk_nexttoken,
    END = prsd2_cjk_end,
    LEXTYPES = prsd2_cjk_lextype,
    HEADLINE = prsd2_cjk_headline);

CREATE TEXT SEARCH CONFIGURATION public.config_2_gram_cjk (
    PARSER = pg_cjk_parser
);

SET default_text_search_config = 'public.config_2_gram_cjk';

Now you can execute the sql demonstrated in the introduction section to see the results.

There is a Dockerfile in this repository which helps you build a docker image based on postgres:12.

docker build -t postgres:12-dev . --build-arg POSTGRES_VERSION=12 -f Dockerfile_alpine

or you can build a docker image based on postgres:16.

docker build -t postgres:16-dev . --build-arg POSTGRES_VERSION=16 -f Dockerfile_alpine

or you can build a docker image based on postgres:11.

docker build -t postgres:11-dev . -f Dockerfile_pg11

If you use this image to start an instance of postgres:12, all you need to do is to create the extension, search parser and configuration in pgAdmin.

Connect to your server via pgAdmin or other clients and then execute the following sql to create the pg_cjk_parser extension.

CREATE EXTENSION pg_cjk_parser;

Then you should create a search configuration and make it default.

CREATE TEXT SEARCH PARSER public.pg_cjk_parser (
    START = prsd2_cjk_start,
    GETTOKEN = prsd2_cjk_nexttoken,
    END = prsd2_cjk_end,
    LEXTYPES = prsd2_cjk_lextype,
    HEADLINE = prsd2_cjk_headline);

CREATE TEXT SEARCH CONFIGURATION public.config_2_gram_cjk (
    PARSER = pg_cjk_parser
);

SET default_text_search_config = 'public.config_2_gram_cjk';

Now you can execute the sql demonstrated in the introduction section to see the results.

Suppose you have an docker instance of postgres name postgres_db_1 whose image is postgres:12.

docker cp pg_cjk_parser.so postgres_db_1:/usr/lib/postgresql/12/lib/

Connect to the postgres instance via pgAdmin or other clients and then execute the following sql

CREATE FUNCTION public.prsd2_cjk_nexttoken(IN internal, IN internal, IN internal)
    RETURNS internal
    LANGUAGE 'c' STRICT
    
AS '$libdir/pg_cjk_parser.so', 'prsd2_nexttoken'
;

	
CREATE FUNCTION public.prsd2_cjk_end(IN internal)
    RETURNS void
    LANGUAGE 'c' STRICT
    
AS '$libdir/pg_cjk_parser.so', 'prsd2_end'
;

CREATE FUNCTION public.prsd2_cjk_lextype(IN internal)
    RETURNS internal
    LANGUAGE 'c' STRICT
    
AS '$libdir/pg_cjk_parser.so', 'prsd2_lextype'
;

	
CREATE FUNCTION public.prsd2_cjk_headline(IN internal, IN internal, IN tsquery)
    RETURNS internal
    LANGUAGE 'c' STRICT
    
AS '$libdir/pg_cjk_parser.so', 'prsd2_headline'
;

Then you should create a search configuration and make it default.

CREATE TEXT SEARCH PARSER public.pg_cjk_parser (
    START = prsd2_cjk_start,
    GETTOKEN = prsd2_cjk_nexttoken,
    END = prsd2_cjk_end,
    LEXTYPES = prsd2_cjk_lextype,
    HEADLINE = prsd2_cjk_headline);

CREATE TEXT SEARCH CONFIGURATION public.config_2_gram_cjk (
    PARSER = pg_cjk_parser
);

SET default_text_search_config = 'public.config_2_gram_cjk';

Now you can execute the sql demonstrated in the introduction section to see the results.

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR asciihword
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR cjk
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR email
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR asciiword
    WITH english_stem;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR entity
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR file
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR float
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR host
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR hword
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR hword_asciipart
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR hword_numpart
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR hword_part
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR int
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR numhword
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR numword
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR protocol
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR sfloat
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR tag
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR uint
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR url
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR url_path
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR version
    WITH simple;

ALTER TEXT SEARCH CONFIGURATION public.config_2_gram_cjk
    ADD MAPPING FOR word
    WITH simple;

Now you can use to_tsvector and to_tsquery to test the newly created search configuration.

SELECT to_tsvector('Doraemnon Nobita「ドラえもん のび太の牧場物語」多拉A梦 野比大雄χΨψΩω'), to_tsquery('のび太'), 
to_tsquery('野比大雄'),
to_tsvector('Doraemnon Nobita「ドラえもん のび太の牧場物語」多拉A梦 野比大雄χΨψΩω') @@ to_tsquery('のび太'),
to_tsvector('Doraemnon Nobita「ドラえもん のび太の牧場物語」多拉A梦 野比大雄χΨψΩω') @@ to_tsquery('野比大雄');

SELECT to_tsvector('大韩民国개인정보의 수집 및 이용 목적(「개인정보 보호법」 제15조)'), to_tsquery('「大韩民国개인정보');

PG_CJK Parser is a derived work based on PostgreSQL source code 'src/backend/tsearch/wparser_def.c'. The license of this derived work is the same as that of PostgreSQL source code.

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Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group

Portions Copyright (c) 1994, The Regents of the University of California

Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies.

IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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