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Diffstat (limited to 'docs/ref/databases.txt')
| -rw-r--r-- | docs/ref/databases.txt | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/docs/ref/databases.txt b/docs/ref/databases.txt index 3b23a9dd51..4256395d78 100644 --- a/docs/ref/databases.txt +++ b/docs/ref/databases.txt @@ -630,6 +630,11 @@ the ``SELECT ... FOR UPDATE`` statement. If ``select_for_update()`` is used with ``nowait=True``, ``skip_locked=True``, or ``of`` then a :exc:`~django.db.NotSupportedError` is raised. +When using ``select_for_update()`` on MySQL, make sure you filter a queryset +against at least set of fields contained in unique constraints or only against +fields covered by indexes. Otherwise, an exclusive write lock will be acquired +over the full table for the duration of the transaction. + Automatic typecasting can cause unexpected results -------------------------------------------------- |