9.13. Text Search Functions and Operators

Table 9-37, Table 9-38 and Table 9-39 summarize the functions and operators that are provided for full text searching. See Chapter 12 for a detailed explanation of PostgreSQL's text search facility.

Table 9-37. Text Search Operators

@@ tsvector matches tsquery ?to_tsvector('fat cats ate rats') @@ to_tsquery('cat & rat')t
@@@ deprecated synonym for @@to_tsvector('fat cats ate rats') @@@ to_tsquery('cat & rat')t
|| concatenate tsvectors'a:1 b:2'::tsvector || 'c:1 d:2 b:3'::tsvector'a':1 'b':2,5 'c':3 'd':4
&& AND tsquerys together'fat | rat'::tsquery && 'cat'::tsquery( 'fat' | 'rat' ) & 'cat'
|| OR tsquerys together'fat | rat'::tsquery || 'cat'::tsquery( 'fat' | 'rat' ) | 'cat'
!! negate a tsquery!! 'cat'::tsquery!'cat'
@> tsquery contains another ?'cat'::tsquery @> 'cat & rat'::tsqueryf
<@ tsquery is contained in ?'cat'::tsquery <@ 'cat & rat'::tsqueryt

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 9-38. Text Search Functions

FunctionReturn TypeDescriptionExampleResult
get_current_ts_config() regconfigget default text search configurationget_current_ts_config()english
length(tsvector) integernumber of lexemes in tsvectorlength('fat:2,4 cat:3 rat:5A'::tsvector)3
numnode(tsquery) integernumber of lexemes plus operators in tsquery numnode('(fat & rat) | cat'::tsquery)5
plainto_tsquery([ config regconfig , ] query text) tsqueryproduce tsquery ignoring punctuationplainto_tsquery('english', 'The Fat Rats')'fat' & 'rat'
querytree(query tsquery) textget indexable part of a tsqueryquerytree('foo & ! bar'::tsquery)'foo'
setweight(tsvector, "char") tsvectorassign weight to each element of tsvectorsetweight('fat:2,4 cat:3 rat:5B'::tsvector, 'A')'cat':3A 'fat':2A,4A 'rat':5A
strip(tsvector) tsvectorremove positions and weights from tsvectorstrip('fat:2,4 cat:3 rat:5A'::tsvector)'cat' 'fat' 'rat'
to_tsquery([ config regconfig , ] query text) tsquerynormalize words and convert to tsqueryto_tsquery('english', 'The & Fat & Rats')'fat' & 'rat'
to_tsvector([ config regconfig , ] document text) tsvectorreduce document text to tsvectorto_tsvector('english', 'The Fat Rats')'fat':2 'rat':3
ts_headline([ config regconfig, ] document text, query tsquery [, options text ]) textdisplay a query matchts_headline('x y z', 'z'::tsquery)x y <b>z</b>
ts_rank([ weights float4[], ] vector tsvector, query tsquery [, normalization integer ]) float4rank document for queryts_rank(textsearch, query)0.818
ts_rank_cd([ weights float4[], ] vector tsvector, query tsquery [, normalization integer ]) float4rank document for query using cover densityts_rank_cd('{0.1, 0.2, 0.4, 1.0}', textsearch, query)2.01317
ts_rewrite(query tsquery, target tsquery, substitute tsquery) tsqueryreplace target with substitute within queryts_rewrite('a & b'::tsquery, 'a'::tsquery, 'foo|bar'::tsquery)'b' & ( 'foo' | 'bar' )
ts_rewrite(query tsquery, select text)tsqueryreplace using targets and substitutes from a SELECT commandSELECT ts_rewrite('a & b'::tsquery, 'SELECT t,s FROM aliases')'b' & ( 'foo' | 'bar' )
tsvector_update_trigger() triggertrigger function for automatic tsvector column updateCREATE TRIGGER ... tsvector_update_trigger(tsvcol, 'pg_catalog.swedish', title, body)
tsvector_update_trigger_column() triggertrigger function for automatic tsvector column updateCREATE 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 9-39 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 9-39. Text Search Debugging Functions

FunctionReturn TypeDescriptionExampleResult
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 recordtest a configurationts_debug('english', 'The Brightest supernovaes')(asciiword,"Word, all ASCII",The,{english_stem},english_stem,{}) ...
ts_lexize(dict regdictionary, token text) text[]test a dictionaryts_lexize('english_stem', 'stars'){star}
ts_parse(parser_name text, document text, OUT tokid integer, OUT token text) setof recordtest a parserts_parse('default', 'foo - bar')(1,foo) ...
ts_parse(parser_oid oid, document text, OUT tokid integer, OUT token text)setof recordtest a parserts_parse(3722, 'foo - bar')(1,foo) ...
ts_token_type(parser_name text, OUT tokid integer, OUT alias text, OUT description text) setof recordget token types defined by parserts_token_type('default')(1,asciiword,"Word, all ASCII") ...
ts_token_type(parser_oid oid, OUT tokid integer, OUT alias text, OUT description text)setof recordget token types defined by parserts_token_type(3722)(1,asciiword,"Word, all ASCII") ...
ts_stat(sqlquery text, [ weights text, ] OUT word text, OUT ndoc integer, OUT nentry integer) setof recordget statistics of a tsvector columnts_stat('SELECT vector from apod')(foo,10,15) ...