From 2a038521c4eabdc5f6d5026d3dd6d22868e329cd Mon Sep 17 00:00:00 2001
From: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Date: Tue, 18 Feb 2020 11:45:12 +0100
Subject: [PATCH] Fixed #31271 -- Preserved ordering when unifying query
 parameters on Oracle.

This caused misplacing parameters in logged SQL queries.

Regression in 79065b55a70cd220820a260a1c54851b7be0615a.

Thanks Hans Aarne Liblik for the report.
---
 django/db/backends/oracle/base.py | 5 ++++-
 docs/releases/3.0.4.txt           | 3 +++
 tests/backends/tests.py           | 4 ++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 652e3235217..4d2f5b51f1a 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -500,7 +500,10 @@ class FormatStylePlaceholderCursor:
             # 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)
diff --git a/docs/releases/3.0.4.txt b/docs/releases/3.0.4.txt
index 7be1ed15cee..216bc29b0e2 100644
--- a/docs/releases/3.0.4.txt
+++ b/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`).
diff --git a/tests/backends/tests.py b/tests/backends/tests.py
index ce3b863016d..f20d3db5f1d 100644
--- a/tests/backends/tests.py
+++ b/tests/backends/tests.py
@@ -79,6 +79,10 @@ class LastExecutedQueryTest(TestCase):
         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()
             with qs.query.get_compiler(DEFAULT_DB_ALIAS).execute_sql(CURSOR) as cursor: