I'm familiar with Python generators, however I've just come across the term "generative method" which I am not familiar with and cannot find a satisfactory definition.
To put it in context, I found the term in SQLAlchemy's narrative documentation:
Full control of the “autocommit” behavior is available using the generative Connection.execution_options() method provided on Connection, Engine, Executable, using the “autocommit” flag which will turn on or off the autocommit for the selected scope.
What is a generative method? Trying to iterate the object returned by Connection.execution_options() doesn't work so I'm figuring it's something other than a standard generator.
It doesn't appear to be a common database concept, but SQLAlchemy uses the term generative in the sense "generated by your program iteratively at runtime". (So, no connection to python generators). An example from the tutorial:
The Query object is fully generative, meaning that most method calls
return a new Query object upon which further criteria may be added.
For example, to query for users named “ed” with a full name of “Ed
Jones”, you can call filter() twice, which joins criteria using AND:
>>> for user in session.query(User).\
... filter(User.name=='ed').\
... filter(User.fullname=='Ed Jones'):
... print user
This call syntax is more commonly known as "method chaining", and the design that allows it as a "fluent interface".
So, in the case of Connection.execution_options(), "generative" means that it returns the modified connection object, so that you can chain the calls as above.
Looking at the source code of Connection.execution_options (lib/sqlalchemy/engine/base.py), all that method does is add options to the connection.
The idea is that those options influence the future behaviour of e.g. queries.
As an example:
result = connection.execution_options(stream_results=True).\
execute(stmt)
Here, the behaviour was changed in the middle of the connection for just this query.
In a way, it "generates" or clones itself as an object that has a slightly different behaviour.
Here you can also set autocommit to True. Example
# obtain a connection
connection = ...
# do some stuff
# for the next section we want autocommit on
autocommitting_connection = connection.execution_options(autocommit=True)
autocommitting_connection.execute(some_insert)
result = autocommitting_connection.execute(some_query)
# done with this section. Continue using connection (no autocommit)
This is what is meant with that section of the documentation. "generative method" refers to a method that returns a modified copy of the same instance that you can continue working with. This is applicable to the classes Connection, Engine, Executable.
You would have to consult the specific documentation or source code of that project to really make sure, but I would guess that it returns a modified version of some object adapted to the requirements/behaviour defined by the arguments.
The documentation states:
The method returns a copy of this Connection which references the same
underlying DBAPI connection, but also defines the given execution
options which will take effect for a call to execute().
As @zzzeek comments above, this is now documented in the SQLAlchemy glossary.
generative means:
A term that SQLAlchemy uses to refer what’s normally known as method chaining; see that term for details.
And method chaining is:
An object-oriented technique whereby the state of an object is constructed by calling methods on the object. The object features any number of methods, each of which return a new object (or in some cases the same object) with additional state added to the object.
