Fixed #23853 -- Added Join class to replace JoinInfo

Also removed Query.join_map. This structure was used to speed up join
reuse calculation. Initial benchmarking shows that this isn't actually
needed. If there are use cases where the removal has real-world
performance implications, it should be relatively straightforward to
reintroduce it as map {alias: [Join-like objects]}.

django/db/models/sql/compiler.py

@@ -37,7 +37,7 @@ class SQLCompiler(object):
         # cleaned. We are not using a clone() of the query here.
         """
         if not self.query.tables:
-            self.query.join((None, self.query.get_meta().db_table, None))
+            self.query.get_initial_alias()
         if (not self.query.select and self.query.default_cols and not
                 self.query.included_inherited_models):
             self.query.setup_inherited_models()
@@ -171,7 +171,6 @@ class SQLCompiler(object):
 
         # Finally do cleanup - get rid of the joins we created above.
         self.query.reset_refcounts(refcounts_before)
-
         return ' '.join(result), tuple(params)
 
     def as_nested_sql(self):
@@ -511,51 +510,27 @@ class SQLCompiler(object):
         ordering and distinct must be done first.
         """
         result = []
-        qn = self.quote_name_unless_alias
+        params = []
-        qn2 = self.connection.ops.quote_name
-        first = True
-        from_params = []
         for alias in self.query.tables:
             if not self.query.alias_refcount[alias]:
                 continue
             try:
-                name, alias, join_type, lhs, join_cols, _, join_field = self.query.alias_map[alias]
+                from_clause = self.query.alias_map[alias]
             except KeyError:
                 # Extra tables can end up in self.tables, but not in the
                 # alias_map if they aren't in a join. That's OK. We skip them.
                 continue
-            alias_str = '' if alias == name else (' %s' % alias)
+            clause_sql, clause_params = self.compile(from_clause)
-            if join_type and not first:
+            result.append(clause_sql)
-                extra_cond = join_field.get_extra_restriction(
+            params.extend(clause_params)
-                    self.query.where_class, alias, lhs)
-                if extra_cond:
-                    extra_sql, extra_params = self.compile(extra_cond)
-                    extra_sql = 'AND (%s)' % extra_sql
-                    from_params.extend(extra_params)
-                else:
-                    extra_sql = ""
-                result.append('%s %s%s ON ('
-                        % (join_type, qn(name), alias_str))
-                for index, (lhs_col, rhs_col) in enumerate(join_cols):
-                    if index != 0:
-                        result.append(' AND ')
-                    result.append('%s.%s = %s.%s' %
-                    (qn(lhs), qn2(lhs_col), qn(alias), qn2(rhs_col)))
-                result.append('%s)' % extra_sql)
-            else:
-                connector = '' if first else ', '
-                result.append('%s%s%s' % (connector, qn(name), alias_str))
-            first = False
         for t in self.query.extra_tables:
             alias, _ = self.query.table_alias(t)
             # Only add the alias if it's not already present (the table_alias()
-            # calls increments the refcount, so an alias refcount of one means
+            # call increments the refcount, so an alias refcount of one means
-            # this is the only reference.
+            # this is the only reference).
             if alias not in self.query.alias_map or self.query.alias_refcount[alias] == 1:
-                connector = '' if first else ', '
+                result.append(', %s' % self.quote_name_unless_alias(alias))
-                result.append('%s%s' % (connector, qn(alias)))
+        return result, params
-                first = False
-        return result, from_params
 
     def get_grouping(self, having_group_by, ordering_group_by):
         """

django/db/models/sql/constants.py

@@ -21,12 +21,6 @@ GET_ITERATOR_CHUNK_SIZE = 100
 
 # Namedtuples for sql.* internal use.
 
-# Join lists (indexes into the tuples that are values in the alias_map
-# dictionary in the Query class).
-JoinInfo = namedtuple('JoinInfo',
-                      'table_name rhs_alias join_type lhs_alias '
-                      'join_cols nullable join_field')
-
 # Pairs of column clauses to select, and (possibly None) field for the clause.
 SelectInfo = namedtuple('SelectInfo', 'col field')
 
@@ -41,3 +35,7 @@ ORDER_DIR = {
     'ASC': ('ASC', 'DESC'),
     'DESC': ('DESC', 'ASC'),
 }
+
+# SQL join types.
+INNER = 'INNER JOIN'
+LOUTER = 'LEFT OUTER JOIN'

django/db/models/sql/datastructures.py

@@ -2,6 +2,7 @@
 Useful auxiliary data structures for query construction. Not useful outside
 the SQL domain.
 """
+from django.db.models.sql.constants import INNER, LOUTER
 
 
 class EmptyResultSet(Exception):
@@ -22,3 +23,119 @@ class MultiJoin(Exception):
 
 class Empty(object):
     pass
+
+
+class Join(object):
+    """
+    Used by sql.Query and sql.SQLCompiler to generate JOIN clauses into the
+    FROM entry. For example, the SQL generated could be
+        LEFT OUTER JOIN "sometable" T1 ON ("othertable"."sometable_id" = "sometable"."id")
+
+    This class is primarily used in Query.alias_map. All entries in alias_map
+    must be Join compatible by providing the following attributes and methods:
+        - table_name (string)
+        - table_alias (possible alias for the table, can be None)
+        - join_type (can be None for those entries that aren't joined from
+          anything)
+        - parent_alias (which table is this join's parent, can be None similarly
+          to join_type)
+        - as_sql()
+        - relabeled_clone()
+
+    """
+    def __init__(self, table_name, parent_alias, table_alias, join_type,
+                 join_field, nullable):
+        # Join table
+        self.table_name = table_name
+        self.parent_alias = parent_alias
+        # Note: table_alias is not necessarily known at instantiation time.
+        self.table_alias = table_alias
+        # LOUTER or INNER
+        self.join_type = join_type
+        # A list of 2-tuples to use in the ON clause of the JOIN.
+        # Each 2-tuple will create one join condition in the ON clause.
+        self.join_cols = join_field.get_joining_columns()
+        # Along which field (or RelatedObject in the reverse join case)
+        self.join_field = join_field
+        # Is this join nullabled?
+        self.nullable = nullable
+
+    def as_sql(self, compiler, connection):
+        """
+        Generates the full
+           LEFT OUTER JOIN sometable ON sometable.somecol = othertable.othercol, params
+        clause for this join.
+        """
+        params = []
+        sql = []
+        alias_str = '' if self.table_alias == self.table_name else (' %s' % self.table_alias)
+        qn = compiler.quote_name_unless_alias
+        qn2 = connection.ops.quote_name
+        sql.append('%s %s%s ON (' % (self.join_type, qn(self.table_name), alias_str))
+        for index, (lhs_col, rhs_col) in enumerate(self.join_cols):
+            if index != 0:
+                sql.append(' AND ')
+            sql.append('%s.%s = %s.%s' % (
+                qn(self.parent_alias),
+                qn2(lhs_col),
+                qn(self.table_alias),
+                qn2(rhs_col),
+            ))
+        extra_cond = self.join_field.get_extra_restriction(
+            compiler.query.where_class, self.table_alias, self.parent_alias)
+        if extra_cond:
+            extra_sql, extra_params = compiler.compile(extra_cond)
+            extra_sql = 'AND (%s)' % extra_sql
+            params.extend(extra_params)
+            sql.append('%s' % extra_sql)
+        sql.append(')')
+        return ' '.join(sql), params
+
+    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)
+        return self.__class__(
+            self.table_name, new_parent_alias, new_table_alias, self.join_type,
+            self.join_field, self.nullable)
+
+    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
+
+    def demote(self):
+        new = self.relabeled_clone({})
+        new.join_type = INNER
+        return new
+
+    def promote(self):
+        new = self.relabeled_clone({})
+        new.join_type = LOUTER
+        return new
+
+
+class BaseTable(object):
+    """
+    The BaseTable class is used for base table references in FROM clause. For
+    example, the SQL "foo" in
+        SELECT * FROM "foo" WHERE somecond
+    could be generated by this class.
+    """
+    join_type = None
+    parent_alias = None
+
+    def __init__(self, table_name, alias):
+        self.table_name = table_name
+        self.table_alias = alias
+
+    def as_sql(self, compiler, connection):
+        alias_str = '' if self.table_alias == self.table_name else (' %s' % self.table_alias)
+        base_sql = compiler.quote_name_unless_alias(self.table_name)
+        return base_sql + alias_str, []
+
+    def relabeled_clone(self, change_map):
+        return self.__class__(self.table_name, change_map.get(self.table_alias, self.table_alias))

django/db/models/sql/query.py

@@ -20,8 +20,9 @@ from django.db.models.query_utils import Q, refs_aggregate
 from django.db.models.related import PathInfo
 from django.db.models.aggregates import Count
 from django.db.models.sql.constants import (QUERY_TERMS, ORDER_DIR, SINGLE,
-        ORDER_PATTERN, JoinInfo, SelectInfo)
+        ORDER_PATTERN, SelectInfo, INNER, LOUTER)
-from django.db.models.sql.datastructures import EmptyResultSet, Empty, MultiJoin
+from django.db.models.sql.datastructures import (
+    EmptyResultSet, Empty, MultiJoin, Join, BaseTable)
 from django.db.models.sql.where import (WhereNode, Constraint, EverythingNode,
     ExtraWhere, AND, OR, EmptyWhere)
 from django.utils import six
@@ -87,10 +88,6 @@ class Query(object):
     """
     A single SQL query.
     """
-    # SQL join types. These are part of the class because their string forms
-    # vary from database to database and can be customised by a subclass.
-    INNER = 'INNER JOIN'
-    LOUTER = 'LEFT OUTER JOIN'
 
     alias_prefix = 'T'
     subq_aliases = frozenset([alias_prefix])
@@ -103,15 +100,15 @@ class Query(object):
         self.alias_refcount = {}
         # alias_map is the most important data structure regarding joins.
         # It's used for recording which joins exist in the query and what
-        # type they are. The key is the alias of the joined table (possibly
+        # types they are. The key is the alias of the joined table (possibly
-        # the table name) and the value is JoinInfo from constants.py.
+        # the table name) and the value is a Join-like object (see
+        # sql.datastructures.Join for more information).
         self.alias_map = {}
         # Sometimes the query contains references to aliases in outer queries (as
         # a result of split_exclude). Correct alias quoting needs to know these
         # aliases too.
         self.external_aliases = set()
         self.table_map = {}     # Maps table names to list of aliases.
-        self.join_map = {}
         self.default_cols = True
         self.default_ordering = True
         self.standard_ordering = True
@@ -246,7 +243,6 @@ class Query(object):
         obj.alias_map = self.alias_map.copy()
         obj.external_aliases = self.external_aliases.copy()
         obj.table_map = self.table_map.copy()
-        obj.join_map = self.join_map.copy()
         obj.default_cols = self.default_cols
         obj.default_ordering = self.default_ordering
         obj.standard_ordering = self.standard_ordering
@@ -495,19 +491,17 @@ class Query(object):
         self.get_initial_alias()
         joinpromoter = JoinPromoter(connector, 2, False)
         joinpromoter.add_votes(
-            j for j in self.alias_map if self.alias_map[j].join_type == self.INNER)
+            j for j in self.alias_map if self.alias_map[j].join_type == INNER)
         rhs_votes = set()
         # Now, add the joins from rhs query into the new query (skipping base
         # table).
         for alias in rhs.tables[1:]:
-            table, _, join_type, lhs, join_cols, nullable, join_field = rhs.alias_map[alias]
+            join = rhs.alias_map[alias]
             # If the left side of the join was already relabeled, use the
             # updated alias.
-            lhs = change_map.get(lhs, lhs)
+            join = join.relabeled_clone(change_map)
-            new_alias = self.join(
+            new_alias = self.join(join, reuse=reuse)
-                (lhs, table, join_cols), reuse=reuse,
+            if join.join_type == INNER:
-                nullable=nullable, join_field=join_field)
-            if join_type == self.INNER:
                 rhs_votes.add(new_alias)
             # We can't reuse the same join again in the query. If we have two
             # distinct joins for the same connection in rhs query, then the
@@ -714,27 +708,26 @@ class Query(object):
         aliases = list(aliases)
         while aliases:
             alias = aliases.pop(0)
-            if self.alias_map[alias].join_cols[0][1] is None:
+            if self.alias_map[alias].join_type is None:
                 # This is the base table (first FROM entry) - this table
                 # isn't really joined at all in the query, so we should not
                 # alter its join type.
                 continue
             # Only the first alias (skipped above) should have None join_type
             assert self.alias_map[alias].join_type is not None
-            parent_alias = self.alias_map[alias].lhs_alias
+            parent_alias = self.alias_map[alias].parent_alias
             parent_louter = (
                 parent_alias
-                and self.alias_map[parent_alias].join_type == self.LOUTER)
+                and self.alias_map[parent_alias].join_type == LOUTER)
-            already_louter = self.alias_map[alias].join_type == self.LOUTER
+            already_louter = self.alias_map[alias].join_type == LOUTER
             if ((self.alias_map[alias].nullable or parent_louter) and
                     not already_louter):
-                data = self.alias_map[alias]._replace(join_type=self.LOUTER)
+                self.alias_map[alias] = self.alias_map[alias].promote()
-                self.alias_map[alias] = data
                 # Join type of 'alias' changed, so re-examine all aliases that
                 # refer to this one.
                 aliases.extend(
                     join for join in self.alias_map.keys()
-                    if (self.alias_map[join].lhs_alias == alias
+                    if (self.alias_map[join].parent_alias == alias
                         and join not in aliases))
 
     def demote_joins(self, aliases):
@@ -750,10 +743,10 @@ class Query(object):
         aliases = list(aliases)
         while aliases:
             alias = aliases.pop(0)
-            if self.alias_map[alias].join_type == self.LOUTER:
+            if self.alias_map[alias].join_type == LOUTER:
-                self.alias_map[alias] = self.alias_map[alias]._replace(join_type=self.INNER)
+                self.alias_map[alias] = self.alias_map[alias].demote()
-                parent_alias = self.alias_map[alias].lhs_alias
+                parent_alias = self.alias_map[alias].parent_alias
-                if self.alias_map[parent_alias].join_type == self.INNER:
+                if self.alias_map[parent_alias].join_type == INNER:
                     aliases.append(parent_alias)
 
     def reset_refcounts(self, to_counts):
@@ -792,19 +785,13 @@ class Query(object):
                 (key, relabel_column(col)) for key, col in self._annotations.items())
 
         # 2. Rename the alias in the internal table/alias datastructures.
-        for ident, aliases in self.join_map.items():
-            del self.join_map[ident]
-            aliases = tuple(change_map.get(a, a) for a in aliases)
-            ident = (change_map.get(ident[0], ident[0]),) + ident[1:]
-            self.join_map[ident] = aliases
         for old_alias, new_alias in six.iteritems(change_map):
-            alias_data = self.alias_map.get(old_alias)
+            if old_alias not in self.alias_map:
-            if alias_data is None:
                 continue
-            alias_data = alias_data._replace(rhs_alias=new_alias)
+            alias_data = self.alias_map[old_alias].relabeled_clone(change_map)
+            self.alias_map[new_alias] = alias_data
             self.alias_refcount[new_alias] = self.alias_refcount[old_alias]
             del self.alias_refcount[old_alias]
-            self.alias_map[new_alias] = alias_data
             del self.alias_map[old_alias]
 
             table_aliases = self.table_map[alias_data.table_name]
@@ -819,14 +806,6 @@ class Query(object):
         for key, alias in self.included_inherited_models.items():
             if alias in change_map:
                 self.included_inherited_models[key] = change_map[alias]
-
-        # 3. Update any joins that refer to the old alias.
-        for alias, data in six.iteritems(self.alias_map):
-            lhs = data.lhs_alias
-            if lhs in change_map:
-                data = data._replace(lhs_alias=change_map[lhs])
-                self.alias_map[alias] = data
-
         self.external_aliases = {change_map.get(alias, alias)
                                  for alias in self.external_aliases}
 
@@ -862,7 +841,7 @@ class Query(object):
             alias = self.tables[0]
             self.ref_alias(alias)
         else:
-            alias = self.join((None, self.get_meta().db_table, None))
+            alias = self.join(BaseTable(self.get_meta().db_table, None))
         return alias
 
     def count_active_tables(self):
@@ -873,7 +852,7 @@ class Query(object):
         """
         return len([1 for count in self.alias_refcount.values() if count])
 
-    def join(self, connection, reuse=None, nullable=False, join_field=None):
+    def join(self, join, reuse=None):
         """
         Returns an alias for the join in 'connection', either reusing an
         existing alias for that join or creating a new one. 'connection' is a
@@ -897,40 +876,22 @@ class Query(object):
 
         The 'join_field' is the field we are joining along (if any).
         """
-        lhs, table, join_cols = connection
+        reuse = [a for a, j in self.alias_map.items()
-        assert lhs is None or join_field is not None
+                 if (reuse is None or a in reuse) and j == join]
-        existing = self.join_map.get(connection, ())
+        if reuse:
-        if reuse is None:
+            self.ref_alias(reuse[0])
-            reuse = existing
+            return reuse[0]
-        else:
-            reuse = [a for a in existing if a in reuse]
-        for alias in reuse:
-            if join_field and self.alias_map[alias].join_field != join_field:
-                # The join_map doesn't contain join_field (mainly because
-                # fields in Query structs are problematic in pickling), so
-                # check that the existing join is created using the same
-                # join_field used for the under work join.
-                continue
-            self.ref_alias(alias)
-            return alias
 
         # No reuse is possible, so we need a new alias.
-        alias, _ = self.table_alias(table, create=True)
+        alias, _ = self.table_alias(join.table_name, create=True)
-        if not lhs:
+        if join.join_type:
-            # Not all tables need to be joined to anything. No join type
+            if self.alias_map[join.parent_alias].join_type == LOUTER or join.nullable:
-            # means the later columns are ignored.
+                join_type = LOUTER
-            join_type = None
+            else:
-        elif self.alias_map[lhs].join_type == self.LOUTER or nullable:
+                join_type = INNER
-            join_type = self.LOUTER
+            join.join_type = join_type
-        else:
+        join.table_alias = alias
-            join_type = self.INNER
-        join = JoinInfo(table, alias, join_type, lhs, join_cols or ((None, None),), nullable,
-                        join_field)
         self.alias_map[alias] = join
-        if connection in self.join_map:
-            self.join_map[connection] += (alias,)
-        else:
-            self.join_map[connection] = (alias,)
         return alias
 
     def setup_inherited_models(self):
@@ -1249,7 +1210,7 @@ class Query(object):
             require_outer = True
             if (lookup_type != 'isnull' and (
                     self.is_nullable(targets[0]) or
-                    self.alias_map[join_list[-1]].join_type == self.LOUTER)):
+                    self.alias_map[join_list[-1]].join_type == LOUTER)):
                 # The condition added here will be SQL like this:
                 # NOT (col IS NOT NULL), where the first NOT is added in
                 # upper layers of code. The reason for addition is that if col
@@ -1326,7 +1287,7 @@ class Query(object):
         # rel_a doesn't produce any rows, then the whole condition must fail.
         # So, demotion is OK.
         existing_inner = set(
-            (a for a in self.alias_map if self.alias_map[a].join_type == self.INNER))
+            (a for a in self.alias_map if self.alias_map[a].join_type == INNER))
         clause, require_inner = self._add_q(where_part, self.used_aliases)
         self.where.add(clause, AND)
         for hp in having_parts:
@@ -1490,10 +1451,9 @@ class Query(object):
                 nullable = self.is_nullable(join.join_field)
             else:
                 nullable = True
-            connection = alias, opts.db_table, join.join_field.get_joining_columns()
+            connection = Join(opts.db_table, alias, None, INNER, join.join_field, nullable)
             reuse = can_reuse if join.m2m else None
-            alias = self.join(
+            alias = self.join(connection, reuse=reuse)
-                connection, reuse=reuse, nullable=nullable, join_field=join.join_field)
             joins.append(alias)
         if hasattr(final_field, 'field'):
             final_field = final_field.field
@@ -1991,9 +1951,10 @@ class Query(object):
         for trimmed_paths, path in enumerate(all_paths):
             if path.m2m:
                 break
-            if self.alias_map[lookup_tables[trimmed_paths + 1]].join_type == self.LOUTER:
+            if self.alias_map[lookup_tables[trimmed_paths + 1]].join_type == LOUTER:
                 contains_louter = True
-            self.unref_alias(lookup_tables[trimmed_paths])
+            alias = lookup_tables[trimmed_paths]
+            self.unref_alias(alias)
         # The path.join_field is a Rel, lets get the other side's field
         join_field = path.join_field.field
         # Build the filter prefix.
@@ -2010,7 +1971,7 @@ class Query(object):
         # Lets still see if we can trim the first join from the inner query
         # (that is, self). We can't do this for LEFT JOINs because we would
         # miss those rows that have nothing on the outer side.
-        if self.alias_map[lookup_tables[trimmed_paths + 1]].join_type != self.LOUTER:
+        if self.alias_map[lookup_tables[trimmed_paths + 1]].join_type != LOUTER:
             select_fields = [r[0] for r in join_field.related_fields]
             select_alias = lookup_tables[trimmed_paths + 1]
             self.unref_alias(lookup_tables[trimmed_paths])
@@ -2024,6 +1985,12 @@ class Query(object):
             # values in select_fields. Lets punt this one for now.
             select_fields = [r[1] for r in join_field.related_fields]
             select_alias = lookup_tables[trimmed_paths]
+        # The found starting point is likely a Join instead of a BaseTable reference.
+        # But the first entry in the query's FROM clause must not be a JOIN.
+        for table in self.tables:
+            if self.alias_refcount[table] > 0:
+                self.alias_map[table] = BaseTable(self.alias_map[table].table_name, table)
+                break
         self.select = [SelectInfo((select_alias, f.column), f) for f in select_fields]
         return trimmed_prefix, contains_louter
 

tests/queries/tests.py

@@ -11,6 +11,7 @@ from django.core.exceptions import FieldError
 from django.db import connection, DEFAULT_DB_ALIAS
 from django.db.models import Count, F, Q
 from django.db.models.sql.where import WhereNode, EverythingNode, NothingNode
+from django.db.models.sql.constants import LOUTER
 from django.db.models.sql.datastructures import EmptyResultSet
 from django.test import TestCase, skipUnlessDBFeature
 from django.test.utils import CaptureQueriesContext
@@ -128,7 +129,7 @@ class Queries1Tests(BaseQuerysetTest):
     def test_ticket2306(self):
         # Checking that no join types are "left outer" joins.
         query = Item.objects.filter(tags=self.t2).query
-        self.assertNotIn(query.LOUTER, [x[2] for x in query.alias_map.values()])
+        self.assertNotIn(LOUTER, [x.join_type for x in query.alias_map.values()])
 
         self.assertQuerysetEqual(
             Item.objects.filter(Q(tags=self.t1)).order_by('name'),
@@ -336,7 +337,7 @@ class Queries1Tests(BaseQuerysetTest):
 
         # Excluding from a relation that cannot be NULL should not use outer joins.
         query = Item.objects.exclude(creator__in=[self.a1, self.a2]).query
-        self.assertNotIn(query.LOUTER, [x[2] for x in query.alias_map.values()])
+        self.assertNotIn(LOUTER, [x.join_type for x in query.alias_map.values()])
 
         # Similarly, when one of the joins cannot possibly, ever, involve NULL
         # values (Author -> ExtraInfo, in the following), it should never be
@@ -344,7 +345,7 @@ class Queries1Tests(BaseQuerysetTest):
         # involve one "left outer" join (Author -> Item is 0-to-many).
         qs = Author.objects.filter(id=self.a1.id).filter(Q(extra__note=self.n1) | Q(item__note=self.n3))
         self.assertEqual(
-            len([x[2] for x in qs.query.alias_map.values() if x[2] == query.LOUTER and qs.query.alias_refcount[x[1]]]),
+            len([x for x in qs.query.alias_map.values() if x.join_type == LOUTER and qs.query.alias_refcount[x.table_alias]]),
             1
         )
 
@@ -855,7 +856,7 @@ class Queries1Tests(BaseQuerysetTest):
         )
         q = Note.objects.filter(Q(extrainfo__author=self.a1) | Q(extrainfo=xx)).query
         self.assertEqual(
-            len([x[2] for x in q.alias_map.values() if x[2] == q.LOUTER and q.alias_refcount[x[1]]]),
+            len([x for x in q.alias_map.values() if x.join_type == LOUTER and q.alias_refcount[x.table_alias]]),
             1
         )