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Projects/Full Text Search/User Guide

Contents

Full Text Search - User Guide

Overview

This document aims to help developers that need to develop a functionality that uses this technology. This is a very fast/simple introduction, for more details at database level regarding this technology, please refer to the Postgres' Full Text Search Documentation


Technical concepts

The filtering of Full Text Search in Postgres uses a special data types and Postgres provides functions to convert what we usually have, which is text into what we need. The filtering happens as following, with the text in which we want to search we need to create a TSVector and to operate with a TSVector we need a TSQuery and @@ special operator.

SELECT ...
FROM ...
WHERE ...
AND to_tsvector('<language>', '<text_in_which_to_search>') @@ to_tsquery('<language>', '<query text>')

Database elements

Normally searches are made in great collections and this in database means tables with many rows. Being like this it's desirable to have an index, there are special indexes to operate with TSVectors but then this requires to create a column.

How to create the column

ALTER TABLE Table_Name ADD COLUMN FTS_Col TSVECTOR;

How to create the index

CREATE INDEX FTS_Col_idx ON Table_Name USING GIN (FTS_Col);

How to populate the newly created column

When creating a module that creates a TSVector column in a table it might be necessary to create a modulescript that populates the existing rows.

UPDATE Table_Name SET FTS_Col = to_tsvector('<language>', '<text_in_which_to_search>') WHERE condition;
 
UPDATE Table_Name SET FTS_Col = to_tsvector('<language>', '<text_column_which_to_search>') WHERE condition;
 
UPDATE Table_Name SET FTS_Col = to_tsvector('<language>', '<text_column1_which_to_search>') || to_tsvector('<language>', '<text_column2_which_to_search>') WHERE condition;
 
UPDATE Table_Name SET FTS_Col = setweight(to_tsvector('<language>', '<text_column1_which_to_search>'), 'A') || setweight(to_tsvector('<language>', '<text_column2_which_to_search>'), 'D') WHERE condition;

How to rank/order by matches

SELECT ts_rank_cd(FTS_Col, to_tsquery('<language>', '<query_text>')), ...
FROM Table_Name
WHERE text_column1_which_to_search @@ to_tsquery('<language>', '<query_text>')
ORDER BY 1;

Functions created at hibernate level

Although the TSVector columns are not available at hibernate level, there are two functions that have been created to allow to use filtering and ranking at hibernate level. These functions do nothing at hibernate level but parse the SQL necessary to filter or rank.

The functions created are fullTextSearchFilter and fullTextSearchRank and they can be called like this:

AND fullTextSearchFilter(<alias_of_hibernate_entity_in_hql>, <sql_name_of_column>, '<language>', '<query_text>') IS true
 
fullTextSearchRank(<alias_of_hibernate_entity_in_hql>, <sql_name_of_column>, '<language>', '<query_text>')

Retrieved from "http://wiki.openbravo.com/wiki/Projects/Full_Text_Search/User_Guide"

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