Fixed #29886 -- Fixed unaccent lookup when PostgreSQL's standard_conforming_strings option is off.

Thanks Tom McClure for the patch.

django/db/backends/postgresql/base.py

@@ -121,7 +121,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     #
     # Note: we use str.format() here for readability as '%' is used as a wildcard for
     # the LIKE operator.
-    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, '\', '\\'), '%%', '\%%'), '_', '\_')"
+    pattern_esc = r"REPLACE(REPLACE(REPLACE({}, E'\\', E'\\\\'), E'%%', E'\\%%'), E'_', E'\\_')"
     pattern_ops = {
         'contains': "LIKE '%%' || {} || '%%'",
         'icontains': "LIKE '%%' || UPPER({}) || '%%'",

tests/postgres_tests/test_unaccent.py

@@ -1,3 +1,4 @@
+from django.db import connection
 from django.test import modify_settings
 
 from . import PostgreSQLTestCase
@@ -42,6 +43,24 @@ class UnaccentTest(PostgreSQLTestCase):
             ordered=False
         )
 
+    def test_unaccent_with_conforming_strings_off(self):
+        """SQL is valid when standard_conforming_strings is off."""
+        with connection.cursor() as cursor:
+            cursor.execute('SHOW standard_conforming_strings')
+            disable_conforming_strings = cursor.fetchall()[0][0] == 'on'
+            if disable_conforming_strings:
+                cursor.execute('SET standard_conforming_strings TO off')
+            try:
+                self.assertQuerysetEqual(
+                    self.Model.objects.filter(field__unaccent__endswith='éÖ'),
+                    ['àéÖ', 'aeO'],
+                    transform=lambda instance: instance.field,
+                    ordered=False,
+                )
+            finally:
+                if disable_conforming_strings:
+                    cursor.execute('SET standard_conforming_strings TO on')
+
     def test_unaccent_accentuated_needle(self):
         self.assertQuerysetEqual(
             self.Model.objects.filter(field__unaccent="aéÖ"),