PostgreSQL, warn once per connection per missing OID. Closes #14275.

[Yves Senn & Matthew Draper]

3 files changed, 19 insertions, 2 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c0264df8e1..00ea49fa9d 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   PostgreSQL adapter only warns once for every missing OID per connection.
+
+    Fixes #14275.
+
+    *Matthew Draper*, *Yves Senn*
+
 *   PostgreSQL adapter automatically reloads it's type map when encountering
     unknown OIDs.
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 207e1c4fed..0485093123 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -565,8 +565,8 @@ module ActiveRecord
           end
 
           type_map.fetch(oid, fmod) {
-            warn "unknown OID #{oid}: failed to recognize type of #{column_name}"
-            OID::Identity.new
+            warn "unknown OID #{oid}: failed to recognize type of '#{column_name}'. It will be treated as String."
+            type_map[oid] = OID::Identity.new
           }
         end
 
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index d319bd0b80..b7791078db 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -385,6 +385,17 @@ module ActiveRecord
         reset_connection
       end
 
+      def test_only_warn_on_first_encounter_of_unknown_oid
+        warning = capture(:stderr) {
+          @connection.select_all "SELECT NULL::anyelement"
+          @connection.select_all "SELECT NULL::anyelement"
+          @connection.select_all "SELECT NULL::anyelement"
+        }
+        assert_match(/\Aunknown OID \d+: failed to recognize type of 'anyelement'. It will be treated as String.\n\z/, warning)
+      ensure
+        reset_connection
+      end
+
       private
       def insert(ctx, data)
         binds   = data.map { |name, value|