What does operator <=> do in PostgreSQL

May 24, 2024

I found such query in some of the working repository:

SELECT id, full_name_tsvector <=> plainto_tsquery('English', 'test') AS rank
FROM names_tsvectors 
WHERE "full_name_tsvector" @@ plainto_tsquery('English', 'test')
ORDER BY rank LIMIT 1000

The query gives result:

id   |rank     |
-----+---------+
 6574|13.159472|
25653|13.159472|
 5730|13.159472|
21924|13.159472|
 6578|13.159472|
 5813|13.159472|
22188| 16.44934|
21959| 16.44934|
20360| 16.44934|

So my question is – what does operator <=> do actually? I haven’t found anything about that operator except that it does not exist in Postgres.

>Solution :

PostgreSQL doesn’t contain an operator with that name. You probably got it from an extension.

Figure out which extension that is using the query

SELECT oprname AS operator_name,
       oprnamespace::regnamespace AS operator_schema,
       e.extname AS extension_name
FROM pg_operator AS o
   JOIN pg_depend AS d
      ON d.classid = 'pg_operator'::regclass
         AND d.objid = o.oid
   JOIN pg_extension AS e
      ON d.refclassid = 'pg_extension'::regclass
         AND d.refobjid = e.oid
WHERE d.deptype = 'e'
  AND o.oprname = '<=>';

and look at the documentation of that software.