#Installing the zhparser Extension

#Overview

zhparser is a PostgreSQL full-text search parser for Chinese, based on SCWS. It is pre-bundled in the Spilo image shipped with the PostgreSQL Operator, so you only need to create the extension and a text-search configuration that uses it.

#Prerequisites

• A running PostgreSQL cluster managed by the PostgreSQL Operator.
• A database user with privileges to create extensions (the postgres superuser, used below). Managing the custom dictionary requires superuser privileges.

#Procedure

#1. Create the extension

CREATE EXTENSION IF NOT EXISTS zhparser;

#2. Create a text-search configuration

CREATE TEXT SEARCH CONFIGURATION testzhcfg (PARSER = zhparser);
ALTER TEXT SEARCH CONFIGURATION testzhcfg ADD MAPPING FOR n,v,a,i,e,l WITH simple;

#3. Tokenize and build search vectors

-- Inspect raw tokenization
SELECT * FROM ts_parse('zhparser', '保障房资金压力');

-- Build a tsvector using the configuration created above
SELECT to_tsvector('testzhcfg', '2011年保障房进入了更大规模的建设阶段');

-- Build a tsquery
SELECT to_tsquery('testzhcfg', '保障房资金压力');

#Custom dictionary

The custom dictionary is scoped per database (not per instance) and is stored under the data directory. Adding custom words requires superuser privileges.

-- Add a custom word
INSERT INTO zhparser.zhprs_custom_word VALUES ('资金压力');

-- Synchronize the dictionary
SELECT sync_zhprs_custom_word();

Re-establish your session (reconnect) for the change to take effect. After that, 资金压力 is tokenized as a single word instead of 资金 + 压力.

#Parser configuration

The following options control dictionary loading and tokenization behavior (PostgreSQL 9.2+). All default to false:

SHOW zhparser.punctuation_ignore;
ALTER SYSTEM SET zhparser.punctuation_ignore = true;
SELECT pg_reload_conf();

zhparser.extra_dicts and zhparser.dict_in_memory must be set before the backend starts (set them in the configuration and reload; new connections pick them up). The other options can be set per session.

#Upgrading the extension

ALTER EXTENSION zhparser UPDATE;

#Verification

SELECT extname, extversion FROM pg_extension WHERE extname = 'zhparser';