[3.0.x] Fixed #31271 -- Preserved ordering when unifying query parame…

…ters on Oracle.

This caused misplacing parameters in logged SQL queries.

Regression in 79065b5.

Thanks Hans Aarne Liblik for the report.
Backport of 2a03852 from master

django/db/backends/oracle/base.py

@@ -497,7 +497,10 @@ def _fix_for_params(self, query, params, unify_by_values=False):
             # params_dict = {0.75: ':arg0', 2: ':arg1', 'sth': ':arg2'}
             # args = [':arg0', ':arg1', ':arg0', ':arg2', ':arg0']
             # params = {':arg0': 0.75, ':arg1': 2, ':arg2': 'sth'}
-            params_dict = {param: ':arg%d' % i for i, param in enumerate(set(params))}
+            params_dict = {
+                param: ':arg%d' % i
+                for i, param in enumerate(dict.fromkeys(params))
+            }
             args = [params_dict[param] for param in params]
             params = {value: key for key, value in params_dict.items()}
             query = query % tuple(args)

docs/releases/3.0.4.txt

@@ -20,3 +20,6 @@ Bugfixes
   related fields or parent link fields with :ref:`multi-table-inheritance` in
   the ``of`` argument, the corresponding models were not locked
   (:ticket:`31246`).
+
+* Fixed a regression in Django 3.0 that caused misplacing parameters in logged
+  SQL queries on Oracle (:ticket:`31271`).

tests/backends/tests.py

@@ -79,6 +79,10 @@ def test_last_executed_query(self):
         for qs in (
             Article.objects.filter(pk=1),
             Article.objects.filter(pk__in=(1, 2), reporter__pk=3),
+            Article.objects.filter(
+                pk=1,
+                reporter__pk=9,
+            ).exclude(reporter__pk__in=[2, 1]),
         ):
             sql, params = qs.query.sql_with_params()
             cursor = qs.query.get_compiler(DEFAULT_DB_ALIAS).execute_sql(CURSOR)