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Refs #23853 -- Updated sql.query.Query.join() docstring.

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Follow up to ab89414f40.
This commit is contained in:
Tim Graham
2017-06-13 14:16:52 -04:00
committed by GitHub
parent be68c0bf63
commit 7acbe89cc2
1 changed files with 7 additions and 18 deletions
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25
django/db/models/sql/query.py
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@@ -894,27 +894,16 @@ class Query:
def join(self, join, reuse=None):
"""
Return an alias for the join in 'connection', either reusing an
existing alias for that join or creating a new one. 'connection' is a
tuple (lhs, table, join_cols) where 'lhs' is either an existing
table alias or a table name. 'join_cols' is a tuple of tuples containing
columns to join on ((l_id1, r_id1), (l_id2, r_id2)). The join corresponds
to the SQL equivalent of::
Return an alias for the 'join', either reusing an existing alias for
that join or creating a new one. 'join' is either a
sql.datastructures.BaseTable or Join.
lhs.l_id1 = table.r_id1 AND lhs.l_id2 = table.r_id2
The 'reuse' parameter can be either None which means all joins
(matching the connection) are reusable, or it can be a set containing
the aliases that can be reused.
The 'reuse' parameter can be either None which means all joins are
reusable, or it can be a set containing the aliases that can be reused.
A join is always created as LOUTER if the lhs alias is LOUTER to make
sure we do not generate chains like t1 LOUTER t2 INNER t3. All new
joins are created as LOUTER if nullable is True.
If 'nullable' is True, the join can potentially involve NULL values and
is a candidate for promotion (to "left outer") when combining querysets.
The 'join_field' is the field we are joining along (if any).
sure chains like t1 LOUTER t2 INNER t3 aren't generated. All new
joins are created as LOUTER if the join is nullable.
"""
reuse = [a for a, j in self.alias_map.items()
if (reuse is None or a in reuse) and j == join]