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: http://www.sai.msu.su/~megera/wiki/tprewriter
Дата изменения: Unknown Дата индексирования: Sun Apr 10 17:50:12 2016 Кодировка: UTF-8 Поисковые слова: lmc |
This module was designed specially for travelpost project. Design notes of full text search are available from tp search en.
FUNCTIONS: select tp_rewrite (query::tsquery, keyword::tsquery) select tp_rewrite (ARRAY[query::tsquery, test.keyword] ) from test select tp_rewrite (query::tsquery,'select test.keyword from test'::text); - Here, column test.keyword is of type tsquery. - Rewrite original query by changing '&' to '|'. Integrity of complex keyword is preserved by using '&' to minimize possible noise. example: Rewrite query 'new & york & hotel' and preserve 'new & york' regression=# select tp_rewrite(to_tsquery('new&york&hotel'),to_tsquery('new&york')); tp_rewrite -------------------------- 'hotel' | 'york' & 'new' regression=# select tp_rewrite( ARRAY['new&york&hotel'::tsquery, test.keyword] ) from test; tp_rewrite -------------------------- 'hotel' | 'york' & 'new' regression=# select tp_rewrite( 'new&york&hotel'::tsquery,'select test.keyword from test'::text); tp_rewrite -------------------------- 'hotel' | 'york' & 'new' Note: tp_rewrite supports multiple keywords, but result depends on the order of keywords. Intersected keywords: 'new & york & city' - original query, new & york', 'new & city' - keywords, then tp_rewrite could produce two variants: 'new & york | city' 'new | york & city' Embedded keywords: 'new & york & city & hotel' - original query, 'new & york & city', 'new & city' - keywords, then tp_rewrite could produce two variants: 'new & york & city | hotel' 'new & city | york | hotel' --------------------------------------------------------------------------- tp_substitute(query::tsquery,target::tsquery,sample::tsquery) tp_substitute(ARRAY[query::tsquery,target::tsquery,sample::tsquery]) from test; tp_substitute(query::tsquery, 'select test.target,test.sample from test'); - Here, columns test.target and test.sample are of type tsquery. - substitute part of original query (sample) by specified target. example: Expand city name by its aliases. regression=# select tp_substitute('new & york & hotel','new & york', 'nyc|gotham |big& apple'); tp_substitute ------------------------------------------------------ 'hotel' & ( 'apple' & 'big' | ( 'nyc' | 'gotham' ) ) Note: tp_substitute doesn't supports embedded substitutions, only first target will expands. For example, if we have aliases (in followin order!): 'new & york & city' -> 'new & york | nyc' and 'new & york' -> 'gotham', then query 'new & york & city & hotel' will be '(new & york | nyc) & hotel' --------------------------------------------------------------------------- tp_rewrite_substitute(query::tsquery,target::tsquery,sample::tsquery) tp_rewrite_substitute(ARRAY[query::tsquery,target::tsquery,sample::tsquery]) from test; tp_rewrite_substitute(query::tsquery,'select test.target,test.sample from test'); - combines tp_substitute and tp_rewrite functions in this order. example: Expand city name by its aliases and preserve integrity of city name. regression=# select tp_rewrite_substitute('new & york & hotel','new & york', 'nyc|gotham|big& apple'); tp_rewrite_substitute ------------------------------------------------------ 'hotel' | ( 'apple' & 'big' | ( 'nyc' | 'gotham' ) ) regression=# select tp_rewrite_substitute(ARRAY['new & york & hotel', test.target, test.sample]) from test; tp_rewrite_substitute ----------------------------------------------------------- 'hotel' | ( 'nyc' | ( 'appl' & 'big' | 'york' & 'new' ) ) regression=# select tp_rewrite_substitute('select test.target, test.sample from test','new & york & hotel'); tp_rewrite_substitute ----------------------------------------------------------- 'hotel' | ( 'nyc' | ( 'appl' & 'big' | 'york' & 'new' ) ) OPERATORS: tsquery @ tsquery - TRUE if right agrument *might* contained in left argument tsquery ~ tsquery - TRUE if left agrument *might* contained in right argument - these operators could be use to speedup tp_* functions filtering out non-candidate tuples from table with samples. example: Check tuples iff test.target contained in query. regression=# select tp_rewrite_substitute(ARRAY[query, test.target, test.sample]) from test, to_tsquery('new & york & hotel') as query where query @ test.target; tp_rewrite_substitute ----------------------------------------------------------- 'hotel' | ( 'nyc' | ( 'appl' & 'big' | 'york' & 'new' ) ) note: it's safe to use coalesce(tp_rewrite(ARRAY[...]),query), because tp_rewrite(ARRAY[...]) returns NULL if query @ test.target fail (nothing found). INDEX SUPPORT: It's possible to create index to speedup operators @, ~. example: create index sample_idx on test using gist(sample gist_tp_tsquery_ops); Documentation TODO: 1 добавлена ф-ция int4 numnode( TSQUERY ) Возвращает суммарное число операндов и операций (проще говоря - число узлов в перставлении запроса как дерево) 2 операции < <= = <> >= > (следует отметить, что меньше-больше отношения для запросов величина странная и абстрактная, никакой реальной пользы из этого извлень нельзя, кроме быстрого поиска на совпадение. Единственно, что гарантируется - однозначность такого сравнения) 3 BTree index on tsquery