diff options
Diffstat (limited to 'lib/sqlalchemy/sql/annotation.py')
| -rw-r--r-- | lib/sqlalchemy/sql/annotation.py | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/annotation.py b/lib/sqlalchemy/sql/annotation.py index 834c93912..e6f6311c4 100644 --- a/lib/sqlalchemy/sql/annotation.py +++ b/lib/sqlalchemy/sql/annotation.py @@ -26,6 +26,13 @@ class Annotated(object): reason of keeping its hash value current. When GC'ed, the hash value may be reused, causing conflicts. + .. note:: The rationale for Annotated producing a brand new class, + rather than placing the functionality directly within ClauseElement, + is **performance**. The __hash__() method is absent on plain + ClauseElement which leads to significantly reduced function call + overhead, as the use of sets and dictionaries against ClauseElement + objects is prevalent, but most are not "annotated". + """ def __new__(cls, *args): |