Fixed #27802 -- Unified return value of db backend datetime SQL methods.

6 files changed, 48 insertions, 57 deletions

diff --git a/django/db/backends/mysql/operations.py b/django/db/backends/mysql/operations.py
index 881ada60c7..b47136df26 100644
--- a/django/db/backends/mysql/operations.py
+++ b/django/db/backends/mysql/operations.py
@@ -44,29 +44,23 @@ class DatabaseOperations(BaseDatabaseOperations):
 
     def _convert_field_to_tz(self, field_name, tzname):
         if settings.USE_TZ:
-            field_name = "CONVERT_TZ(%s, 'UTC', %%s)" % field_name
-            params = [tzname]
-        else:
-            params = []
-        return field_name, params
+            field_name = "CONVERT_TZ(%s, 'UTC', '%s')" % (field_name, tzname)
+        return field_name
 
     def datetime_cast_date_sql(self, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
-        sql = "DATE(%s)" % field_name
-        return sql, params
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return "DATE(%s)" % field_name
 
     def datetime_cast_time_sql(self, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
-        sql = "TIME(%s)" % field_name
-        return sql, params
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return "TIME(%s)" % field_name
 
     def datetime_extract_sql(self, lookup_type, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
-        sql = self.date_extract_sql(lookup_type, field_name)
-        return sql, params
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return self.date_extract_sql(lookup_type, field_name)
 
     def datetime_trunc_sql(self, lookup_type, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
+        field_name = self._convert_field_to_tz(field_name, tzname)
         fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
         format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
         format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
@@ -77,7 +71,7 @@ class DatabaseOperations(BaseDatabaseOperations):
         else:
             format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])
             sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
-        return sql, params
+        return sql
 
     def time_trunc_sql(self, lookup_type, field_name):
         fields = {
diff --git a/django/db/backends/oracle/operations.py b/django/db/backends/oracle/operations.py
index f8fee3bd3d..7cc33af537 100644
--- a/django/db/backends/oracle/operations.py
+++ b/django/db/backends/oracle/operations.py
@@ -122,19 +122,16 @@ WHEN (new.%(col_name)s IS NULL)
 
     def datetime_cast_date_sql(self, field_name, tzname):
         field_name = self._convert_field_to_tz(field_name, tzname)
-        sql = 'TRUNC(%s)' % field_name
-        return sql, []
+        return 'TRUNC(%s)' % field_name
 
     def datetime_cast_time_sql(self, field_name, tzname):
         # Since `TimeField` values are stored as TIMESTAMP where only the date
         # part is ignored, convert the field to the specified timezone.
-        field_name = self._convert_field_to_tz(field_name, tzname)
-        return field_name, []
+        return self._convert_field_to_tz(field_name, tzname)
 
     def datetime_extract_sql(self, lookup_type, field_name, tzname):
         field_name = self._convert_field_to_tz(field_name, tzname)
-        sql = self.date_extract_sql(lookup_type, field_name)
-        return sql, []
+        return self.date_extract_sql(lookup_type, field_name)
 
     def datetime_trunc_sql(self, lookup_type, field_name, tzname):
         field_name = self._convert_field_to_tz(field_name, tzname)
@@ -149,7 +146,7 @@ WHEN (new.%(col_name)s IS NULL)
             sql = "TRUNC(%s, 'MI')" % field_name
         else:
             sql = "CAST(%s AS DATE)" % field_name  # Cast to DATE removes sub-second precision.
-        return sql, []
+        return sql
 
     def time_trunc_sql(self, lookup_type, field_name):
         # The implementation is similar to `datetime_trunc_sql` as both
diff --git a/django/db/backends/postgresql/operations.py b/django/db/backends/postgresql/operations.py
index e612a60ca8..fde02cbb78 100644
--- a/django/db/backends/postgresql/operations.py
+++ b/django/db/backends/postgresql/operations.py
@@ -32,32 +32,25 @@ class DatabaseOperations(BaseDatabaseOperations):
 
     def _convert_field_to_tz(self, field_name, tzname):
         if settings.USE_TZ:
-            field_name = "%s AT TIME ZONE %%s" % field_name
-            params = [tzname]
-        else:
-            params = []
-        return field_name, params
+            field_name = "%s AT TIME ZONE '%s'" % (field_name, tzname)
+        return field_name
 
     def datetime_cast_date_sql(self, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
-        sql = '(%s)::date' % field_name
-        return sql, params
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return '(%s)::date' % field_name
 
     def datetime_cast_time_sql(self, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
-        sql = '(%s)::time' % field_name
-        return sql, params
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return '(%s)::time' % field_name
 
     def datetime_extract_sql(self, lookup_type, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
-        sql = self.date_extract_sql(lookup_type, field_name)
-        return sql, params
+        field_name = self._convert_field_to_tz(field_name, tzname)
+        return self.date_extract_sql(lookup_type, field_name)
 
     def datetime_trunc_sql(self, lookup_type, field_name, tzname):
-        field_name, params = self._convert_field_to_tz(field_name, tzname)
+        field_name = self._convert_field_to_tz(field_name, tzname)
         # https://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
-        sql = "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)
-        return sql, params
+        return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)
 
     def time_trunc_sql(self, lookup_type, field_name):
         return "DATE_TRUNC('%s', %s)::time" % (lookup_type, field_name)
diff --git a/django/db/backends/sqlite3/operations.py b/django/db/backends/sqlite3/operations.py
index 4f66b66de9..dd9669d02d 100644
--- a/django/db/backends/sqlite3/operations.py
+++ b/django/db/backends/sqlite3/operations.py
@@ -70,21 +70,30 @@ class DatabaseOperations(BaseDatabaseOperations):
         # cause a collision with a field name).
         return "django_time_trunc('%s', %s)" % (lookup_type.lower(), field_name)
 
+    def _convert_tzname_to_sql(self, tzname):
+        return "'%s'" % tzname if settings.USE_TZ else 'NULL'
+
     def datetime_cast_date_sql(self, field_name, tzname):
-        return "django_datetime_cast_date(%s, %%s)" % field_name, [tzname]
+        return "django_datetime_cast_date(%s, %s)" % (
+            field_name, self._convert_tzname_to_sql(tzname),
+        )
 
     def datetime_cast_time_sql(self, field_name, tzname):
-        return "django_datetime_cast_time(%s, %%s)" % field_name, [tzname]
+        return "django_datetime_cast_time(%s, %s)" % (
+            field_name, self._convert_tzname_to_sql(tzname),
+        )
 
     def datetime_extract_sql(self, lookup_type, field_name, tzname):
         # Same comment as in date_extract_sql.
-        return "django_datetime_extract('%s', %s, %%s)" % (
-            lookup_type.lower(), field_name), [tzname]
+        return "django_datetime_extract('%s', %s, %s)" % (
+            lookup_type.lower(), field_name, self._convert_tzname_to_sql(tzname),
+        )
 
     def datetime_trunc_sql(self, lookup_type, field_name, tzname):
         # Same comment as in date_trunc_sql.
-        return "django_datetime_trunc('%s', %s, %%s)" % (
-            lookup_type.lower(), field_name), [tzname]
+        return "django_datetime_trunc('%s', %s, %s)" % (
+            lookup_type.lower(), field_name, self._convert_tzname_to_sql(tzname),
+        )
 
     def time_extract_sql(self, lookup_type, field_name):
         # sqlite doesn't support extract, so we fake it with the user-defined
diff --git a/django/db/models/functions/datetime.py b/django/db/models/functions/datetime.py
index 19afc271b5..debf65db3a 100644
--- a/django/db/models/functions/datetime.py
+++ b/django/db/models/functions/datetime.py
@@ -44,8 +44,7 @@ class Extract(TimezoneMixin, Transform):
         lhs_output_field = self.lhs.output_field
         if isinstance(lhs_output_field, DateTimeField):
             tzname = self.get_tzname()
-            sql, tz_params = connection.ops.datetime_extract_sql(self.lookup_name, sql, tzname)
-            params.extend(tz_params)
+            sql = connection.ops.datetime_extract_sql(self.lookup_name, sql, tzname)
         elif isinstance(lhs_output_field, DateField):
             sql = connection.ops.date_extract_sql(self.lookup_name, sql)
         elif isinstance(lhs_output_field, TimeField):
@@ -150,16 +149,14 @@ class TruncBase(TimezoneMixin, Transform):
         inner_sql = inner_sql.replace('%s', '%%s')
         if isinstance(self.output_field, DateTimeField):
             tzname = self.get_tzname()
-            sql, params = connection.ops.datetime_trunc_sql(self.kind, inner_sql, tzname)
+            sql = connection.ops.datetime_trunc_sql(self.kind, inner_sql, tzname)
         elif isinstance(self.output_field, DateField):
             sql = connection.ops.date_trunc_sql(self.kind, inner_sql)
-            params = []
         elif isinstance(self.output_field, TimeField):
             sql = connection.ops.time_trunc_sql(self.kind, inner_sql)
-            params = []
         else:
             raise ValueError('Trunc only valid on DateField, TimeField, or DateTimeField.')
-        return sql, inner_params + params
+        return sql, inner_params
 
     def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
         copy = super().resolve_expression(query, allow_joins, reuse, summarize, for_save)
@@ -237,8 +234,7 @@ class TruncDate(TruncBase):
         # Cast to date rather than truncate to date.
         lhs, lhs_params = compiler.compile(self.lhs)
         tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
-        sql, tz_params = connection.ops.datetime_cast_date_sql(lhs, tzname)
-        lhs_params.extend(tz_params)
+        sql = connection.ops.datetime_cast_date_sql(lhs, tzname)
         return sql, lhs_params
 
 
@@ -254,8 +250,7 @@ class TruncTime(TruncBase):
         # Cast to date rather than truncate to date.
         lhs, lhs_params = compiler.compile(self.lhs)
         tzname = timezone.get_current_timezone_name() if settings.USE_TZ else None
-        sql, tz_params = connection.ops.datetime_cast_time_sql(lhs, tzname)
-        lhs_params.extend(tz_params)
+        sql = connection.ops.datetime_cast_time_sql(lhs, tzname)
         return sql, lhs_params
 
 
diff --git a/docs/releases/2.0.txt b/docs/releases/2.0.txt
index f5e5cd4d7c..8afafb200d 100644
--- a/docs/releases/2.0.txt
+++ b/docs/releases/2.0.txt
@@ -220,7 +220,10 @@ bytestrings in certain code paths.
 Database backend API
 --------------------
 
-* ...
+* The ``DatabaseOperations.datetime_cast_date_sql()``,
+  ``datetime_cast_time_sql()``, ``datetime_trunc_sql()``, and
+  ``datetime_extract_sql()`` methods now return only the SQL to perform the
+  operation instead of SQL and a list of parameters.
 
 Dropped support for Oracle 11.2
 -------------------------------