Text Search Functions and Operators

PostgreSQL 8.3.3 Documentation
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# 9.13. Text Search Functions and Operators

Table 9-35, Table 9-36 and Table 9-37 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 9-35. Text Search Operators

Operator | Description | Example | Result
--- | --- | --- | ---
`@@` | `tsvector` matches `tsquery` ? | `to_tsvector('fat cats ate rats') @@ to_tsquery('cat & rat')` | `t`
`@@@` | same as `@@`, but see Section 12.9 | `to_tsvector('fat cats ate rats') @@@ to_tsquery('cat & rat')` | `t`
`||` | concatenate `tsvector`s | `'a:1 b:2'::tsvector || 'c:1 d:2 b:3'::tsvector` | `'a':1 'b':2,5 'c':3 'd':4`
`&&` | AND `tsquery`s together | `'fat | rat'::tsquery && 'cat'::tsquery` | `( 'fat' | 'rat' ) & 'cat'`
`||` | OR `tsquery`s 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 9-36. Text Search Functions

Function | Return Type | Description | Example | Result
--- | --- | --- | --- | ---
``to_tsvector`([ `config` `regconfig` , ] `document` `text`)` | `tsvector` | reduce document text to `tsvector` | `to_tsvector('english', 'The Fat Rats')` | `'fat':2 'rat':3`
``length`(`tsvector`)` | `integer` | number of lexemes in `tsvector` | `length('fat:2,4 cat:3 rat:5A'::tsvector)` | `3`
``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'`
``plainto_tsquery`([ `config` `regconfig` , ] `query` `text`)` | `tsquery` | produce `tsquery` ignoring punctuation | `plainto_tsquery('english', 'The Fat Rats')` | `'fat' & 'rat'`
``numnode`(`tsquery`)` | `integer` | number of lexemes plus operators in `tsquery` | `numnode('(fat & rat) | cat'::tsquery)` | `5`
``querytree`(`query` `tsquery`)` | `text` | get indexable part of a `tsquery` | `querytree('foo & ! bar'::tsquery)` | `'foo'`
``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_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_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' )`
``get_current_ts_config`()` | `regconfig` | get default text search configuration | `get_current_ts_config()` | `english`
``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 9-37 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 9-37. 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) ...`

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