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: http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/oscon_tsearch2/rank.html
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Function rankReturns a float number that measures the strength of match between a text search vector and a text search query. Rank is typically used to sort matching search results. rank([ weights FLOAT4[], ] tsv TSVECTOR, tsq TSQUERY [, normalization INT4]) RETURNS FLOAT4
SELECT set_curcfg('default_english'); set_curcfg ------------ (1 row) Rank without normalizing by length of ts_vec. SELECT file, title, rank(ts_vec, to_tsquery('create & schema')) FROM postgresql_manual WHERE ts_vec @@ to_tsquery('create & schema') ORDER BY rank(ts_vec, to_tsquery('create & schema')) DESC LIMIT 5; file | title | rank -------------------------+-----------------+---------- sql-createschema.html | CREATE SCHEMA | 0.999717 ddl-schemas.html | Schemas | 0.988608 bookindex.html | Index | 0.971012 sql-createtable.html | CREATE TABLE | 0.636038 sql-createsequence.html | CREATE SEQUENCE | 0.627304 (5 rows) Rank normalizing by logarithm of length of ts_vec. SELECT file, title, rank(ts_vec, to_tsquery('create & schema'), 1) FROM postgresql_manual WHERE ts_vec @@ to_tsquery('create & schema') ORDER BY rank(ts_vec, to_tsquery('create & schema'), 1) DESC LIMIT 5; file | title | rank -------------------------+-----------------+----------- sql-createschema.html | CREATE SCHEMA | 0.164804 ddl-schemas.html | Schemas | 0.138482 bookindex.html | Index | 0.116201 sql-createsequence.html | CREATE SEQUENCE | 0.0955284 sql-grant.html | GRANT | 0.0864042 (5 rows) Rank normalizing by length of ts_vec. SELECT file, title, rank(ts_vec, to_tsquery('create & schema'), 2) FROM postgresql_manual WHERE ts_vec @@ to_tsquery('create & schema') ORDER BY rank(ts_vec, to_tsquery('create & schema'), 2) DESC LIMIT 5; file | title | rank -----------------------+---------------+------------ sql-alterschema.html | ALTER SCHEMA | 0.00333546 sql-createschema.html | CREATE SCHEMA | 0.00231953 sql-dropschema.html | DROP SCHEMA | 0.00146315 sql-createdomain.html | CREATE DOMAIN | 0.00117693 sql-createview.html | CREATE VIEW | 0.00108162 (5 rows) Rank using weights by letter. ALTER TABLE postgresql_manual ADD COLUMN ts_vec_tb tsvector; ALTER TABLE UPDATE postgresql_manual SET ts_vec_tb = concat(setweight(to_tsvector(title), 'A'), setweight(to_tsvector(body), 'B')); UPDATE 592 CREATE INDEX postgresql_manual_tb_in ON postgresql_manual USING gist(ts_vec_tb); CREATE INDEX vacuum full analyze; VACUUM Heavily weighting the title column over the body column. SELECT file, title, rank('{0, 0, 0.01, 0.99}',ts_vec_tb, to_tsquery('create & aggregate')) FROM postgresql_manual WHERE ts_vec_tb @@ to_tsquery('create & aggregate') ORDER BY rank('{0, 0, 0.01, 0.99}', ts_vec_tb, to_tsquery('create & aggregate')) DESC LIMIT 5; file | title | rank --------------------------+-------------------------+----------- sql-createaggregate.html | CREATE AGGREGATE | 0.987949 bookindex.html | Index | 0.151227 xaggr.html | User-Defined Aggregates | 0.0588237 reference.html | Reference | 0.0461835 sql-commands.html | SQL Commands | 0.0461835 (5 rows) Heavily weighting the body column over the title column. SELECT file, title, rank('{0, 0, 0.99, 0.01}',ts_vec_tb, to_tsquery('create & aggregate')) FROM postgresql_manual WHERE ts_vec_tb @@ to_tsquery('create & aggregate') ORDER BY rank('{0, 0, 0.99, 0.01}', ts_vec_tb, to_tsquery('create & aggregate')) DESC LIMIT 5; file | title | rank --------------------------+-------------------------+---------- bookindex.html | Index | 1 xaggr.html | User-Defined Aggregates | 1 sql-createaggregate.html | CREATE AGGREGATE | 1 reference.html | Reference | 0.999998 sql-commands.html | SQL Commands | 0.999998 (5 rows) |