id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
34671	Inspectdb collation issue with oracle views	Philipp Maino	Mariusz Felisiak	"Given a simple oracle table with a primary id column and a VARCHAR column as well as an oracle view that simply selects all column from that table without any manipulation.

When using inspectdb to introspect the **table** we get a {{{models.CharField}}} for the VARCHAR column **without** a {{{db_collation}}} argument.
When using inspectdb to introspect the **view** we get a {{{models.CharField}}} for the VARCHAR column **with** a {{{db_collation}}} argument.

I believe this to be a bug that's being caused by {{{DatabaseIntrospection.get_table_description}}} in ''django/db/backends/oracle/introspection.py''.
This will cause an issue when {{{DiscoverRunner.run_checks}}} triggers {{{CharField._check_db_collation()}}} in ''django/db/models/fields/__init__.py'' as this section will return an error if {{{db_collation is  not None}}}.

**Recreate Issue**
{{{
CREATE TABLE COLLATION_TEST
(
    ID    NUMBER,
    TEST  VARCHAR2(10),
    TEST2 NVARCHAR2(10),
    TEST3 VARCHAR(10)
);
CREATE VIEW COLLATION_TEST_VIEW AS
SELECT *
FROM COLLATION_TEST;
}}}

Run {{{manage.py inspectdb COLLATION_TEST}}}:
{{{
class CollationTest(models.Model):
    id = models.FloatField(blank=True, null=True)
    test = models.CharField(max_length=10, blank=True, null=True)
    test2 = models.CharField(max_length=10, blank=True, null=True)
    test3 = models.CharField(max_length=10, blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'collation_test'
}}}

Run {{{manage.py inspectdb COLLATION_TEST_VIEW}}}.

{{{
class CollationTestView(models.Model):
    id = models.FloatField(blank=True, null=True)
    test = models.CharField(max_length=10, db_collation='USING_NLS_COMP', blank=True, null=True)
    test2 = models.CharField(max_length=10, db_collation='USING_NLS_COMP', blank=True, null=True)
    test3 = models.CharField(max_length=10, db_collation='USING_NLS_COMP', blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'collation_test_view'
}}}

If you consider this as a bug as well then this could be fixed for example by adjusting {{{get_table_description}}}.
You could check first whether {{{table_name}}} is a table or a view by querying {{{user_object}}} as column ''OBJECT_TYPE'' identifies an obhect as ''TABLE' or ""VIEW'.
[[Image(collation.png)]]

If it's a view you have to adjust the introspection query in {{{get_table_description}}} to use {{{user_views}}} instead of {{{user_tables}}}. This will yield the correct CharField definition without db_collation.
{{{
SELECT user_tab_cols.column_name,
       user_tab_cols.data_default,
       CASE
           WHEN user_tab_cols.collation = user_views.default_collation
               THEN NULL
           ELSE user_tab_cols.collation
           END                       collation,
       CASE
           WHEN user_tab_cols.char_used IS NULL
               THEN user_tab_cols.data_length
           ELSE user_tab_cols.char_length
           END                    as display_size,
       CASE
           WHEN user_tab_cols.identity_column = 'YES' THEN 1
           ELSE 0
           END                    as is_autofield,
       CASE
           WHEN EXISTS (SELECT 1
                        FROM user_json_columns
                        WHERE user_json_columns.table_name = user_tab_cols.table_name
                          AND user_json_columns.column_name = user_tab_cols.column_name)
               THEN 1
           ELSE 0
           END                    as is_json,
       user_col_comments.comments as col_comment
FROM user_tab_cols
         LEFT OUTER JOIN
     user_views ON user_views.view_name = user_tab_cols.table_name
         LEFT OUTER JOIN
     user_col_comments ON
                 user_col_comments.column_name = user_tab_cols.column_name AND
                 user_col_comments.table_name = user_tab_cols.table_name
WHERE user_tab_cols.table_name = 'COLLATION_TEST_VIEW'
}}}"	Bug	closed	Core (Management commands)	4.2	Normal	fixed	oracle, inspectdb, collation		Accepted	1	0	0	0	0	0