fix: geojson invalid query on unavailable PostGIS

Closes #4245.

It adds a query on schema cache construction, but doesn't add a new
attribute to the SchemaCache type. We only need the information to be
passed to the `initialMediaHandlers` function to build the builtin media
handlers.

Author: steve-chavez

CHANGELOG.md

@@ -18,6 +18,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Fix OpenAPI broken docs link by @taimoorzaeem in #4080
 - Fix OpenAPI specification incorrectly exposing GET methods for volatile functions by @joelonsql in #4174
 - Fix empty spread embeddings return unexpected SQL error by @taimoorzaeem in #3887
+- Fix `Accept: application/geo+json` generating an invalid query when PostGIS is not available by @steve-chavez in #4245
 
 ### Changed
 

src/PostgREST/SchemaCache.hs

@@ -152,6 +152,7 @@ querySchemaCache conf@AppConfig{..} = do
   reps    <- SQL.statement conf $ dataRepresentations prepared
   mHdlers <- SQL.statement conf $ mediaHandlers prepared
   tzones  <- SQL.statement mempty $ timezones prepared
+  hasPgis <- SQL.statement conf $ postgisFunc prepared
   _       <-
     let sleepCall = SQL.Statement "select pg_sleep($1 / 1000.0)" (param HE.int4) HD.noResult prepared in
     whenJust configInternalSCSleep (`SQL.statement` sleepCall) -- only used for testing
@@ -164,7 +165,7 @@ querySchemaCache conf@AppConfig{..} = do
     , dbRelationships = getOverrideRelationshipsMap rels cRels
     , dbRoutines = funcs
     , dbRepresentations = reps
-    , dbMediaHandlers = HM.union mHdlers initialMediaHandlers -- the custom handlers will override the initial ones
+    , dbMediaHandlers = HM.union mHdlers $ initialMediaHandlers hasPgis -- the custom handlers will override the initial ones
     , dbTimezones = tzones
     }
   where
@@ -1048,12 +1049,14 @@ allViewsKeyDependencies =
       having ncol = array_length(array_agg(row(col.attname, view_columns) order by pks_fks.ord), 1)
       |]
 
-initialMediaHandlers :: MediaHandlerMap
-initialMediaHandlers =
+initialMediaHandlers :: Bool -> MediaHandlerMap
+initialMediaHandlers hasPostgisFunc =
   HM.insert (RelAnyElement, MediaType.MTAny            ) (BuiltinOvAggJson,    MediaType.MTApplicationJSON) $
   HM.insert (RelAnyElement, MediaType.MTApplicationJSON) (BuiltinOvAggJson,    MediaType.MTApplicationJSON) $
   HM.insert (RelAnyElement, MediaType.MTTextCSV        ) (BuiltinOvAggCsv,     MediaType.MTTextCSV) $
-  HM.insert (RelAnyElement, MediaType.MTGeoJSON        ) (BuiltinOvAggGeoJson, MediaType.MTGeoJSON)
+  (if hasPostgisFunc
+    then HM.insert (RelAnyElement, MediaType.MTGeoJSON        ) (BuiltinOvAggGeoJson, MediaType.MTGeoJSON)
+    else mempty)
   HM.empty
 
 mediaHandlers :: Bool -> SQL.Statement AppConfig MediaHandlerMap
@@ -1139,6 +1142,35 @@ timezones = SQL.Statement sql HE.noParams decodeTimezones
     decodeTimezones :: HD.Result TimezoneNames
     decodeTimezones = S.fromList <$> HD.rowList (column HD.text)
 
+
+-- Find the postgis function that has the signature:
+-- st_asgeojson(record,...) returns text
+postgisFunc :: Bool -> SQL.Statement AppConfig Bool
+postgisFunc = SQL.Statement sql params decoder
+  where
+    params =
+      (map escapeIdent . toList . configDbSchemas >$< arrayParam HE.text) <>
+      (map escapeIdent . toList . configDbExtraSearchPath >$< arrayParam HE.text)
+    decoder = HD.singleRow (column HD.bool)
+    sql = encodeUtf8 [trimming|
+    SELECT
+      exists(
+        SELECT
+          1
+        FROM pg_catalog.pg_proc      AS p
+        JOIN pg_catalog.pg_depend    AS d
+          ON  d.objid   = p.oid
+          AND d.deptype = 'e'
+        JOIN pg_catalog.pg_extension AS e
+          ON e.oid   = d.refobjid
+        WHERE p.pronamespace   = ANY($$1::regnamespace[] || $$2::regnamespace[])
+          AND p.proname        = 'st_asgeojson'
+          AND e.extname        = 'postgis'
+          AND p.proargtypes[0] = 'record'::regtype
+          AND pg_get_function_result(p.oid) = 'text'
+      );
+    |]
+
 param :: HE.Value a -> HE.Params a
 param = HE.param . HE.nonNullable
 

test/io/__snapshots__/test_cli/test_schema_cache_snapshot[dbMediaHandlers].yaml

@@ -3,11 +3,6 @@
   - - tag: BuiltinOvAggCsv
     - tag: MTTextCSV
 
-- - - tag: RelAnyElement
-    - tag: MTGeoJSON
-  - - tag: BuiltinOvAggGeoJson
-    - tag: MTGeoJSON
-
 - - - tag: RelAnyElement
     - tag: MTApplicationJSON
   - - tag: BuiltinOvAggJson

test/io/test_io.py

@@ -1137,6 +1137,18 @@ def test_no_pool_connection_required_on_bad_embedding(defaultenv):
         assert response.status_code == 400
 
 
+def test_no_pool_connection_required_on_unavailable_postgis(defaultenv):
+    "no pool connection should be consumed when PostGIS is not available, the request should be quickly rejected at the plan level"
+
+    headers = {
+        "Accept": "application/geo+json",
+    }
+
+    with run(env=defaultenv, no_pool_connection_available=True) as postgrest:
+        response = postgrest.session.get("/projects", headers=headers)
+        assert response.status_code == 406
+
+
 # https://github.com/PostgREST/postgrest/issues/2620
 def test_notify_reloading_catalog_cache(defaultenv):
     "notify should reload the connection catalog cache"