- publishing free software manuals
The PostgreSQL 9.0 Reference Manual - Volume 1A - SQL Language Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 454 pages
ISBN 9781906966041
RRP £14.95 ($19.95)

Sales of this book support the PostgreSQL project! Get a printed copy>>>

7.13 Text Search Functions and Operators

Table 7-36, Table 7-37 and Table 7-38 summarize the functions and operators that are provided for full text searching. See section 10 Full Text Search for a detailed explanation of PostgreSQL's text search facility.

Table 7-36: Text Search Operators
Operator Description
@@ tsvector matches tsquery ?
e.g. to_tsvector('fat cats ate rats') @@ to_tsquery('cat & rat') => t
@@@ deprecated synonym for @@
e.g. to_tsvector('fat cats ate rats') @@@ to_tsquery('cat & rat') => t
|| concatenate tsvectors
e.g. 'a:1 b:2'::tsvector || 'c:1 d:2 b:3'::tsvector => 'a':1 'b':2,5 'c':3 'd':4
&& AND tsquerys together
e.g. 'fat | rat'::tsquery && 'cat'::tsquery => ( 'fat' | 'rat' ) & 'cat'
|| OR tsquerys together
e.g. 'fat | rat'::tsquery || 'cat'::tsquery => ( 'fat' | 'rat' ) | 'cat'
!! negate a tsquery
e.g. !! 'cat'::tsquery => !'cat'
@> tsquery contains another ?
e.g. 'cat'::tsquery @> 'cat & rat'::tsquery => f
<@ tsquery is contained in ?
e.g. 'cat'::tsquery <@ 'cat & rat'::tsquery => t

Note: The tsquery containment operators consider only the lexemes listed in the two queries, ignoring the combining operators.

In addition to the operators shown in the table, the ordinary B-tree comparison operators (=, <, etc) are defined for types tsvector and tsquery. These are not very useful for text searching but allow, for example, unique indexes to be built on columns of these types.

Table 7-37: Text Search Functions
Function Return Type Description
to_tsvector([ config regconfig , ] document text) tsvector reduce document text to tsvector
e.g. to_tsvector('english', 'The Fat Rats') => 'fat':2 'rat':3
length(tsvector) integer number of lexemes in tsvector
e.g. length('fat:2,4 cat:3 rat:5A'::tsvector) => 3
setweight(tsvector, "char") tsvector assign weight to each element of tsvector
e.g. setweight('fat:2,4 cat:3 rat:5B'::tsvector, 'A') => 'cat':3A 'fat':2A,4A 'rat':5A
strip(tsvector) tsvector remove positions and weights from tsvector
e.g. strip('fat:2,4 cat:3 rat:5A'::tsvector) => 'cat' 'fat' 'rat'
to_tsquery([ config regconfig , ] query text) tsquery normalize words and convert to tsquery
e.g. to_tsquery('english', 'The & Fat & Rats') => 'fat' & 'rat'
plainto_tsquery([ config regconfig , ] query text) tsquery produce tsquery ignoring punctuation
e.g. plainto_tsquery('english', 'The Fat Rats') => 'fat' & 'rat'
numnode(tsquery) integer number of lexemes plus operators in tsquery
e.g. numnode('(fat & rat) | cat'::tsquery) => 5
querytree(query tsquery) text get indexable part of a tsquery
e.g. querytree('foo & ! bar'::tsquery) => 'foo'
ts_rank([ weights float4[], ] vector tsvector, query tsquery [, normalization integer ]) float4 rank document for query
e.g. ts_rank(textsearch, query) => 0.818
ts_rank_cd([ weights float4[], ] vector tsvector, query tsquery [, normalization integer ]) float4 rank document for query using cover density
e.g. ts_rank_cd('{0.1, 0.2, 0.4, 1.0}', textsearch, query) => 2.01317
ts_headline([ config regconfig, ] document text, query tsquery [, options text ]) text display a query match
e.g. ts_headline('x y z', 'z'::tsquery) => x y <b>z</b>
ts_rewrite(query tsquery, target tsquery, substitute tsquery) tsquery replace target with substitute within query
e.g. ts_rewrite('a & b'::tsquery, 'a'::tsquery, 'foo|bar'::tsquery) => 'b' & ( 'foo' | 'bar' )
ts_rewrite(query tsquery, select text) tsquery replace using targets and substitutes from a SELECT command
e.g. SELECT ts_rewrite('a & b'::tsquery, 'SELECT t,s FROM aliases') => 'b' & ( 'foo' | 'bar' )
get_current_ts_config() regconfig get default text search configuration
e.g. get_current_ts_config() => english
tsvector_update_trigger() trigger trigger function for automatic tsvector column update
e.g. CREATE TRIGGER ... tsvector_update_trigger(tsvcol, 'pg_catalog.swedish', title, body) =>
tsvector_update_trigger_column() trigger trigger function for automatic tsvector column update
e.g. CREATE TRIGGER ... tsvector_update_trigger_column(tsvcol, configcol, title, body) =>

Note: All the text search functions that accept an optional regconfig argument will use the configuration specified by default_text_search_config when that argument is omitted.

The functions in Table 7-38 are listed separately because they are not usually used in everyday text searching operations. They are helpful for development and debugging of new text search configurations.

Table 7-38: Text Search Debugging Functions
Function Return Type Description
ts_debug([ config regconfig, ] document text, OUT alias text, OUT description text, OUT token text, OUT dictionaries regdictionary[], OUT dictionary regdictionary, OUT lexemes text[]) setof record test a configuration
e.g. ts_debug('english', 'The Brightest supernovaes') => (asciiword,"Word, all ASCII",The,{english_stem},english_stem,{}) ...
ts_lexize(dict regdictionary, token text) text[] test a dictionary
e.g. ts_lexize('english_stem', 'stars') => {star}
ts_parse(parser_name text, document text, OUT tokid integer, OUT token text) setof record test a parser
e.g. ts_parse('default', 'foo - bar') => (1,foo) ...
ts_parse(parser_oid oid, document text, OUT tokid integer, OUT token text) setof record test a parser
e.g. ts_parse(3722, 'foo - bar') => (1,foo) ...
ts_token_type(parser_name text, OUT tokid integer, OUT alias text, OUT description text) setof record get token types defined by parser
e.g. ts_token_type('default') => (1,asciiword,"Word, all ASCII") ...
ts_token_type(parser_oid oid, OUT tokid integer, OUT alias text, OUT description text) setof record get token types defined by parser
e.g. ts_token_type(3722) => (1,asciiword,"Word, all ASCII") ...
ts_stat(sqlquery text, [ weights text, ] OUT word text, OUT ndoc integer, OUT nentry integer) setof record get statistics of a tsvector column
e.g. ts_stat('SELECT vector from apod') => (foo,10,15) ...
ISBN 9781906966041The PostgreSQL 9.0 Reference Manual - Volume 1A - SQL Language ReferenceSee the print edition