Fix cases where delete_records on a has_many association caused errors

because of an ambiguous column name. This happened if the association
model had a default scope that referenced a third table, and the third
table also referenced the original table (with an identical
foreign_key).

Mysql requires that ambiguous columns are deambiguated by using the full
table.column syntax. Postgresql and Sqlite use a different syntax for
updates altogether (and don't tolerate table.name syntax), so the fix
requires always including the full table.column and discarding it later
for Sqlite and Postgresql.

4 files changed, 24 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
index 60a9eee7c7..c97138dfd7 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
@@ -93,6 +93,18 @@ module ActiveRecord
         quote_column_name(table_name)
       end
 
+      # Override to return the quoted table name for assignment. Defaults to
+      # table quoting.
+      #
+      # This works for mysql and mysql2 where table.column can be used to
+      # resolve ambiguity.
+      #
+      # We override this in the sqlite and postgresql adaptors to use only
+      # the column name (as per syntax requirements).
+      def quote_table_name_for_assignment(table, attr)
+        quote_table_name("#{table}.#{attr}")
+      end
+
       def quoted_true
         "'t'"
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
index 791b032023..47e2e3928f 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb
@@ -130,6 +130,10 @@ module ActiveRecord
           end
         end
 
+        def quote_table_name_for_assignment(table, attr)
+          quote_column_name(attr)
+        end
+
         # Quotes column names for use in SQL queries.
         def quote_column_name(name) #:nodoc:
           PGconn.quote_ident(name.to_s)
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 11e8197293..7bead4bde9 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -229,6 +229,10 @@ module ActiveRecord
         @connection.class.quote(s)
       end
 
+      def quote_table_name_for_assignment(table, attr)
+        quote_column_name(attr)
+      end
+
       def quote_column_name(name) #:nodoc:
         %Q("#{name.to_s.gsub('"', '""')}")
       end
diff --git a/activerecord/lib/active_record/sanitization.rb b/activerecord/lib/active_record/sanitization.rb
index 2dad1dc177..3c5b871e99 100644
--- a/activerecord/lib/active_record/sanitization.rb
+++ b/activerecord/lib/active_record/sanitization.rb
@@ -33,10 +33,10 @@ module ActiveRecord
       # Accepts an array, hash, or string of SQL conditions and sanitizes
       # them into a valid SQL fragment for a SET clause.
       #   { name: nil, group_id: 4 }  returns "name = NULL , group_id='4'"
-      def sanitize_sql_for_assignment(assignments)
+      def sanitize_sql_for_assignment(assignments, default_table_name = self.table_name)
         case assignments
         when Array; sanitize_sql_array(assignments)
-        when Hash;  sanitize_sql_hash_for_assignment(assignments)
+        when Hash;  sanitize_sql_hash_for_assignment(assignments, default_table_name)
         else        assignments
         end
       end
@@ -98,9 +98,9 @@ module ActiveRecord
       # Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.
       #   { status: nil, group_id: 1 }
       #     # => "status = NULL , group_id = 1"
-      def sanitize_sql_hash_for_assignment(attrs)
+      def sanitize_sql_hash_for_assignment(attrs, table)
         attrs.map do |attr, value|
-          "#{connection.quote_column_name(attr)} = #{quote_bound_value(value)}"
+          "#{connection.quote_table_name_for_assignment(table, attr)} = #{quote_bound_value(value)}"
         end.join(', ')
       end