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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
| Operator | Description | Example | Result |
|---|---|---|---|
| @@ | 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'::tsquery | f |
| <@ | tsquery is contained in ? | '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 9-38. Text Search Functions
| Function | Return Type | Description | Example | Result |
|---|---|---|---|---|
get_current_ts_config() | regconfig | get default text search configuration | get_current_ts_config() | english |
length(tsvector) | integer | number of lexemes in tsvector | length('fat:2,4 cat:3 rat:5A'::tsvector) | 3 |
numnode(tsquery) | integer | number of lexemes plus operators in tsquery | numnode('(fat & rat) | cat'::tsquery) | 5 |
plainto_tsquery([ config regconfig , ] query text) | tsquery | produce tsquery ignoring punctuation | plainto_tsquery('english', 'The Fat Rats') | 'fat' & 'rat' |
querytree(query tsquery) | text | get indexable part of a tsquery | querytree('foo & ! bar'::tsquery) | 'foo' |
setweight(tsvector, "char") | tsvector | assign weight to each element of tsvector | 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 | 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 | to_tsquery('english', 'The & Fat & Rats') | 'fat' & 'rat' |
to_tsvector([ config regconfig , ] document text) | tsvector | reduce document text to tsvector | to_tsvector('english', 'The Fat Rats') | 'fat':2 'rat':3 |
ts_headline([ config regconfig, ] document text, query tsquery [, options text ]) | text | display a query match | ts_headline('x y z', 'z'::tsquery) | x y <b>z</b> |
ts_rank([ weights float4[], ] vector tsvector, query tsquery [, normalization integer ]) | float4 | rank document for query | 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 | ts_rank_cd('{0.1, 0.2, 0.4, 1.0}', textsearch, query) | 2.01317 |
ts_rewrite(query tsquery, target tsquery, substitute tsquery) | tsquery | replace target with substitute within query | 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 | SELECT ts_rewrite('a & b'::tsquery, 'SELECT t,s FROM aliases') | 'b' & ( 'foo' | 'bar' ) |
tsvector_update_trigger() | trigger | trigger function for automatic tsvector column update | CREATE TRIGGER ... tsvector_update_trigger(tsvcol, 'pg_catalog.swedish', title, body) | |
tsvector_update_trigger_column() | trigger | trigger function for automatic tsvector column update | 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 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
| Function | Return Type | Description | Example | Result |
|---|---|---|---|---|
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 | 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 | ts_lexize('english_stem', 'stars') | {star} |
ts_parse(parser_name text, document text, OUT tokid integer, OUT token text) | setof record | test a parser | 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 | 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 | 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 | 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 | ts_stat('SELECT vector from apod') | (foo,10,15) ... |