问题
I'm trying to use the similarity function in Postgres to do some fuzzy text matching, however whenever I try to use it I get the error:
function similarity(character varying, unknown) does not exist
If I add explicit casts to text I get the error:
function similarity(text, text) does not exist
My query is:
SELECT (similarity("table"."field"::text, %s::text)) AS "similarity", "table".* FROM "table" WHERE similarity > .5 ORDER BY "similarity" DESC LIMIT 10
Do I need to do something to initalize pg_trgm?
回答1:
You have to install pg_trgm. In debian, source this sql: /usr/share/postgresql/8.4/contrib/pg_trgm.sql. From the command line:
psql -f /usr/share/postgresql/8.4/contrib/pg_trgm.sql
Or inside a psql shell:
\i /usr/share/postgresql/8.4/contrib/pg_trgm.sql
The script defaults to installing in the public schema, edit the search path at the top if you want to install it somewhere else (so that uninstalling/upgrading can be done simply by dropping the schema).
回答2:
With postgresql 9.1:
after installing (on ubuntu) sudo apt-get install postgresql-contrib as tomaszbak answered.
you just have to execute the sql command:
CREATE EXTENSION pg_trgm;
回答3:
On ubuntu you need to run
sudo apt-get install postgresql-contrib
to get /usr/share/postgresql/8.4/contrib/pg_trgm.sql
回答4:
If you have the pg_trgm extension installed not in the public schema you must explicitly specify the schema when using the similarity function like this
select schema.similarity(foo,bar) from schema.baz
回答5:
For Postgres 8.4 do following:
As sudo user run:
sudo apt-get install postgresql-contrib-8.4
Switch to postgres user:
sudo su - postgres
Run:
psql -U DB_USER -d DB_NAME -f /usr/share/postgresql/8.4/contrib/pg_trgm.sql
Restart postgres
回答6:
I was having this same issue in the context of running the Django Test Runner against a function that uses the Django 1.11 ORM for trigram similarity on Postgres 9.4.
I had to do a few things to get it working:
1) OP is correct that this required enabling the pg_trgm extension. However, in postgres9.4 this is enabled on a per-database basis. Since Django deletes and recreates the test database with each run, the new test database didn't have the extension installed. To fix this, I initialized the pg_trgm extension within the default newly-created database template in postgres. The command to do this is psql -d template1 -c 'CREATE EXTENSION pg_trgm;' run as the postgres user.
2) Postgres had to be restarted
3) The Django test runner wasn't recognizing this, so I had to upgrade from Django 1.11.12 to 1.11.18 (presumably this is also fixed in newer versions of Django)
来源：https://stackoverflow.com/questions/2254999/similarity-function-in-postgres-with-pg-trgm