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
36464	TupleIn lookup uses tuple containment even if the supports_tuple_lookups feature is disabled for right-hand-side subqueries	Simon Charette	Simon Charette	"Refer to this support request from [https://forum.djangoproject.com/t/need-assistance-for-full-composite-primary-key-support-in-mssql-django/41412/3 the SQL Server third-party backends maintainers].

The problem can be triggered directly when doing `filter(pk__in=queryset)` or indirectly when doing updates that involve related tables as we've not implemented `UPDATE FROM` yet and it is simulated by doing `UPDATE table SET ... WHERE (pk_field0, ..., pk_fieldn) IN (SELECT ... FROM other_table)`.

The latter can be observed in the SQL generated by the `composite_pk.test_update.CompositePKUpdateTests.test_update_token_by_tenant_name` even when `supports_tuple_lookups` is off

{{{#!sql
UPDATE ""composite_pk_token""
SET ""secret"" = 'bar'
WHERE (""composite_pk_token"".""tenant_id"",
       ""composite_pk_token"".""id"") IN
    (SELECT U0.""tenant_id"",
            U0.""id""
     FROM ""composite_pk_token"" U0
     INNER JOIN ""composite_pk_tenant"" U1 ON (U0.""tenant_id"" = U1.""id"")
     WHERE U1.""name"" = 'A')
}}}

Which can be emulated by using `EXISTS` instead

{{{#!sql
UPDATE ""composite_pk_token""
SET ""secret"" = 'bar'
WHERE EXISTS
    (SELECT 1 AS ""a""
     FROM ""composite_pk_token"" U0
     INNER JOIN ""composite_pk_tenant"" U1 ON (U0.""tenant_id"" = U1.""id"")
     WHERE (U1.""name"" = 'A'
            AND ""composite_pk_token"".""tenant_id"" = (U0.""tenant_id"")
            AND ""composite_pk_token"".""id"" = (U0.""id""))
     LIMIT 1)
}}}

Note that we didn't run into issues before because even if we have test coverage for this case the sole backend we test against that has `supports_tuple_lookups` disabled (Oracle < 23.4) happens to support tuple comparisons for subqueries. It feels like it should nonetheless be solved in Django itself."	Bug	closed	Database layer (models, ORM)	5.2	Release blocker	fixed	CompositePrimaryKey		Ready for checkin	1	0	0	0	0	0