使用填充有PostGIS WKB坐标的Postgres array []会导致“函数st_dwithin（文本，几何，整数）不是唯一的”

Question

I'm using Postgres 9.1 and PostGIS 2.

Example query which doesn't work :

SELECT
  *
FROM measurement m
JOIN (SELECT unnest(array['002000000100000000404ff25e353f7cee401d01da7b0b3919']) AS p) AS ps
  ON ST_DWithin(ps.p, m.groundtruth, 5)

Example query which works :

SELECT
  *
FROM measurement m
JOIN (SELECT 1) AS foo
  ON ST_DWithin('002000000100000000404ff25e353f7cee401d01da7b0b3919', m.groundtruth, 5)

And this works, too :

SELECT unnest(array['002000000100000000404ff25e353f7cee401d01da7b0b3919'])

But of course I need the query with the array working.

I call this query from Rails which automatically inserts WKB format (means: I don't know how to change it to WKT, if that's important).

The complete sample Rails code looks like this:

x = [RGeo::Geos.factory.point(63.8935, 6.25181)]
@measurement = Measurement.find_by_sql([radius_search_query, x])

def radius_search_query
  SELECT
    *
  FROM measurement m
  JOIN (SELECT unnest(array[?]) AS p) AS ps
    ON ST_DWithin(ps.p, m.groundtruth, 5)
end

But I've also tested the query from above (without use of ? ) and it keeps failing with the same error message:

ERROR:  function st_dwithin(text, geometry, integer) is not unique
LINE 5:       ON ST_DWithin(ps.p, m.groundtruth, 5)
                 ^
HINT:  Could not choose a best candidate function. You might need to add explicit type casts.

I thought that I maybe have to tell the array that it's of type geometry and not text (as displayed in the error message). But I haven't found a way to do this.

Thank you!!

---

More information:

This doesn't work:

SELECT
  *
FROM measurement m
JOIN (SELECT '002000000100000000404ff25e353f7cee401d01da7b0b3919' as bar) AS foo
  ON ST_DWithin(foo.bar, m.groundtruth, 5)

Error message: failed to find conversion function from unknown to geometry

This works:

SELECT
  *
FROM measurement m
JOIN (SELECT '002000000100000000404ff25e353f7cee401d01da7b0b3919'::geometry(Point) as bar) AS foo
  ON ST_DWithin(foo.bar, m.groundtruth, 5)

Answer 1

After I just found one solution which made the query pretty slow (because of casting values):

SELECT
  *
FROM measurement m
JOIN (SELECT unnest(array['002000000100000000404ff25e353f7cee401d01da7b0b3919']) AS p) AS ps
  ON ST_DWithin(ps.p::geometry(Point), m.groundtruth, 5)

I looked around and stumbled across PostGIS' linestring . And now everything is working!

SELECT
  *
FROM ST_DumpPoints('00200000020000000000000002404ff25e353f7cee401901da7b0b3919404ff25e353f7cee401d01da7b0b3919') AS ps
JOIN measurement m
  ON ST_DWithin(ps.geom, m.groundtruth, 5)

Yay! :-)