This is a document for PGroonga 2.X. See PGroonga 1.x document when you're using old PGroonga.

pgroonga_query_extract_keywords function

Since 1.0.7.

Summary

pgroonga_query_extract_keywords function extract keywords from text that uses query syntax. Query syntax is used by &@~ operator, &@~| operator and so on.

Extracting keywords from query helps you to use pgroonga_snippet_html function, pgroonga_highlight_html function and so on. They require keywords as an argument. Normally, the keywords must be keywords in query.

Syntax

Here is the syntax of this function:

text[] pgroonga_query_extract_keywords(query, index_name DEFAULTS '')

query is a text type value. It uses query syntax.

index_name is a text type value. If you're using query_allow_column=true option with your index, you need to specify the index name.

index_name is available since 3.0.0.

pgroonga_query_extract_keywords returns an array of keywords.

Search terms for AND condition and OR condition are keywords. Search terms for NOT condition aren't keywords. For example, A, B and C are keywords and D isn't keyword in "A (B OR C) - D". - is NOT operator.

Usage

You can get all terms as keywords for AND only case:

SELECT pgroonga_query_extract_keywords('Groonga PostgreSQL') AS query_extract_keywords;
--  query_extract_keywords 
-- ------------------------
--  {PostgreSQL,Groonga}
-- (1 row)

You can get all terms as keywords for OR only case:

SELECT pgroonga_query_extract_keywords('Groonga OR PostgreSQL') AS query_extract_keywords;
--  query_extract_keywords 
-- ------------------------
--  {PostgreSQL,Groonga}
-- (1 row)

You can use parentheses:

SELECT pgroonga_query_extract_keywords('Groonga (MySQL OR PostgreSQL)') AS query_extract_keywords;
--    query_extract_keywords   
-- ----------------------------
--  {Groonga,PostgreSQL,MySQL}
-- (1 row)

Term for NOT condition isn't keyword:

SELECT pgroonga_query_extract_keywords('Groonga - MySQL PostgreSQL') AS query_extract_keywords;
--  query_extract_keywords 
-- ------------------------
--  {PostgreSQL,Groonga}
-- (1 row)

You need to specify index_name when you use query_allow_column=true:

CREATE TABLE memos (
  title text,
  content text
);

CREATE INDEX pgroonga_memo_texts_index
          ON memos
       USING pgroonga (title, content)
        WITH (query_allow_column=true);

SELECT pgroonga_query_extract_keywords(
         'Groonga content:@PostgreSQL',
         index_name => 'pgroonga_memo_texts_index') AS keywords;
--  query_extract_keywords 
-- ------------------------
--  {PostgreSQL,Groonga}
-- (1 row)

See also