refactor: move schemaCacheDescription to SqlFragment

This doesn't belong in the schema cache module, as
it's unused there. It's only used on Query.hs.

src/PostgREST/Query.hs

@@ -36,6 +36,7 @@ import qualified Hasql.Transaction.Sessions        as SQL
 import qualified PostgREST.Error              as Error
 import qualified PostgREST.Query.PreQuery     as PreQuery
 import qualified PostgREST.Query.QueryBuilder as QueryBuilder
+import qualified PostgREST.Query.SqlFragment  as SqlFragment
 import qualified PostgREST.Query.Statements   as Statements
 import qualified PostgREST.SchemaCache        as SchemaCache
 
@@ -205,18 +206,24 @@ actionQuery (MayUseDb plan@InspectPlan{ipSchema=tSchema}) AppConfig{..} _ sCache
       case configOpenApiMode of
         OAFollowPriv -> do
           tableAccess <- SQL.statement [tSchema] (SchemaCache.accessibleTables configDbPreparedStatements)
+          schDesc <- SQL.statement mempty (SQL.dynamicallyParameterized (SqlFragment.schemaDescription tSchema) decodeSchemaDesc configDbPreparedStatements)
+
           MaybeDbResult plan . Just <$> ((,,)
                 (HM.filterWithKey (\qi _ -> S.member qi tableAccess) $ SchemaCache.dbTables sCache)
             <$> SQL.statement ([tSchema], configDbHoistedTxSettings) (SchemaCache.accessibleFuncs configDbPreparedStatements)
-            <*> SQL.statement tSchema (SchemaCache.schemaDescription configDbPreparedStatements))
-        OAIgnorePriv ->
-          (MaybeDbResult plan . Just) . (,,)
-                (HM.filterWithKey (\(QualifiedIdentifier sch _) _ ->  sch == tSchema) $ SchemaCache.dbTables sCache)
-                (HM.filterWithKey (\(QualifiedIdentifier sch _) _ ->  sch == tSchema) $ SchemaCache.dbRoutines sCache)
-            <$> SQL.statement tSchema (SchemaCache.schemaDescription configDbPreparedStatements)
+            <*> pure schDesc)
+        OAIgnorePriv -> do
+          schDesc <- SQL.statement mempty (SQL.dynamicallyParameterized (SqlFragment.schemaDescription tSchema) decodeSchemaDesc configDbPreparedStatements)
+          let tbls = HM.filterWithKey (\(QualifiedIdentifier sch _) _ ->  sch == tSchema) (SchemaCache.dbTables sCache)
+              routs = HM.filterWithKey (\(QualifiedIdentifier sch _) _ ->  sch == tSchema) (SchemaCache.dbRoutines sCache)
+
+          pure $ MaybeDbResult plan (Just (tbls, routs, schDesc))
         OADisabled ->
           pure $ MaybeDbResult plan Nothing
 
+    decodeSchemaDesc :: HD.Result (Maybe Text)
+    decodeSchemaDesc = join <$> HD.rowMaybe (nullableColumn HD.text)
+
 -- Makes sure the querystring pk matches the payload pk
 -- e.g. PUT /items?id=eq.1 { "id" : 1, .. } is accepted,
 -- PUT /items?id=eq.14 { "id" : 2, .. } is rejected.

src/PostgREST/Query/SqlFragment.hs

@@ -40,6 +40,7 @@ module PostgREST.Query.SqlFragment
   , setConfigWithConstantNameJSON
   , escapeIdent
   , escapeIdentList
+  , schemaDescription
   ) where
 
 import qualified Data.Aeson                      as JSON
@@ -590,3 +591,9 @@ handlerF rout = \case
   BuiltinOvAggCsv            -> asCsvF
   CustomFunc funcQi target   -> customFuncF rout funcQi target
   NoAgg                      -> "''::text"
+
+schemaDescription :: Text -> SQL.Snippet
+schemaDescription schema =
+  "SELECT pg_catalog.obj_description(" <> encoded <> "::regnamespace, 'pg_namespace')"
+  where
+    encoded = SQL.encoderAndParam (HE.nonNullable HE.unknown) $ encodeUtf8 schema

src/PostgREST/SchemaCache.hs

@@ -23,7 +23,6 @@ module PostgREST.SchemaCache
   , querySchemaCache
   , accessibleTables
   , accessibleFuncs
-  , schemaDescription
   , showSummary
   ) where
 
@@ -475,12 +474,6 @@ funcsSqlQuery = encodeUtf8 [trimming|
   AND prokind = 'f'
   AND p.pronamespace = ANY($$1::regnamespace[]) |]
 
-schemaDescription :: Bool -> SQL.Statement Schema (Maybe Text)
-schemaDescription =
-    SQL.Statement sql (param HE.text) (join <$> HD.rowMaybe (nullableColumn HD.text))
-  where
-    sql = "SELECT pg_catalog.obj_description($1::regnamespace, 'pg_namespace')"
-
 accessibleTables :: Bool -> SQL.Statement [Schema] AccessSet
 accessibleTables =
   SQL.Statement sql params decodeAccessibleIdentifiers