Fixed #27332 -- Added FilteredRelation API for conditional join (ON clause) support.

Thanks Anssi Kääriäinen for contributing to the patch.

1 files changed, 32 insertions, 10 deletions

diff --git a/django/db/models/sql/datastructures.py b/django/db/models/sql/datastructures.py
index 788c2dd669..ab02f65042 100644
--- a/django/db/models/sql/datastructures.py
+++ b/django/db/models/sql/datastructures.py
@@ -41,7 +41,7 @@ class Join:
         - relabeled_clone()
     """
     def __init__(self, table_name, parent_alias, table_alias, join_type,
-                 join_field, nullable):
+                 join_field, nullable, filtered_relation=None):
         # Join table
         self.table_name = table_name
         self.parent_alias = parent_alias
@@ -56,6 +56,7 @@ class Join:
         self.join_field = join_field
         # Is this join nullabled?
         self.nullable = nullable
+        self.filtered_relation = filtered_relation
 
     def as_sql(self, compiler, connection):
         """
@@ -85,7 +86,11 @@ class Join:
             extra_sql, extra_params = compiler.compile(extra_cond)
             join_conditions.append('(%s)' % extra_sql)
             params.extend(extra_params)
-
+        if self.filtered_relation:
+            extra_sql, extra_params = compiler.compile(self.filtered_relation)
+            if extra_sql:
+                join_conditions.append('(%s)' % extra_sql)
+                params.extend(extra_params)
         if not join_conditions:
             # This might be a rel on the other end of an actual declared field.
             declared_field = getattr(self.join_field, 'field', self.join_field)
@@ -101,18 +106,27 @@ class Join:
     def relabeled_clone(self, change_map):
         new_parent_alias = change_map.get(self.parent_alias, self.parent_alias)
         new_table_alias = change_map.get(self.table_alias, self.table_alias)
+        if self.filtered_relation is not None:
+            filtered_relation = self.filtered_relation.clone()
+            filtered_relation.path = [change_map.get(p, p) for p in self.filtered_relation.path]
+        else:
+            filtered_relation = None
         return self.__class__(
             self.table_name, new_parent_alias, new_table_alias, self.join_type,
-            self.join_field, self.nullable)
+            self.join_field, self.nullable, filtered_relation=filtered_relation,
+        )
+
+    def equals(self, other, with_filtered_relation):
+        return (
+            isinstance(other, self.__class__) and
+            self.table_name == other.table_name and
+            self.parent_alias == other.parent_alias and
+            self.join_field == other.join_field and
+            (not with_filtered_relation or self.filtered_relation == other.filtered_relation)
+        )
 
     def __eq__(self, other):
-        if isinstance(other, self.__class__):
-            return (
-                self.table_name == other.table_name and
-                self.parent_alias == other.parent_alias and
-                self.join_field == other.join_field
-            )
-        return False
+        return self.equals(other, with_filtered_relation=True)
 
     def demote(self):
         new = self.relabeled_clone({})
@@ -134,6 +148,7 @@ class BaseTable:
     """
     join_type = None
     parent_alias = None
+    filtered_relation = None
 
     def __init__(self, table_name, alias):
         self.table_name = table_name
@@ -146,3 +161,10 @@ class BaseTable:
 
     def relabeled_clone(self, change_map):
         return self.__class__(self.table_name, change_map.get(self.table_alias, self.table_alias))
+
+    def equals(self, other, with_filtered_relation):
+        return (
+            isinstance(self, other.__class__) and
+            self.table_name == other.table_name and
+            self.table_alias == other.table_alias
+        )