Better error message for calling columns_hash

When a record does not have a table name, as in the case for a record
with `self.abstract_class = true` and no `self.table_name` set the error
message raises a cryptic:
"ActiveRecord::StatementInvalid: Could not find table ''" this patch now
raises a new `TableNotSpecified Error`

Fixes: #36274

Co-Authored-By: Eugene Kenny <elkenny@gmail.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index 60cf9818c1..c8c06375a3 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -38,6 +38,10 @@ module ActiveRecord
   class AdapterNotSpecified < ActiveRecordError
   end
 
+  # Raised when a model makes a query but it has not specified an associated table.
+  class TableNotSpecified < ActiveRecordError
+  end
+
   # Raised when Active Record cannot find database adapter specified in
   # +config/database.yml+ or programmatically.
   class AdapterNotFound < ActiveRecordError
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 2a45f63d64..18f19af6be 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -482,6 +482,9 @@ module ActiveRecord
         end
 
         def load_schema!
+          unless table_name
+            raise ActiveRecord::TableNotSpecified, "#{self} has no table configured. Set one with #{self}.table_name="
+          end
           @columns_hash = connection.schema_cache.columns_hash(table_name).except(*ignored_columns)
           @columns_hash.each do |name, column|
             define_attribute(