(TLDR: I think bulk_insert_mappings is the wrong function for you to use)
SQLAlchemy consists of 2 main layers. The Core layer deals with SQL
construction, database dialects, connection pooling and so on. The ORM
is built on top of Core, and is intended for people who want to work
with "mapped classes" (such as your User class). The ORM takes
(typically) a Table instance (like your "mytable" object) and connects
a more traditional-looking Python class to it, so that rather than
explicitly inserting, updating and deleting rows in a table, you
create instances of the mapped class and modify its attributes. Older
versions of SQLAlchemy used to require you to declare the tables and
mapped classes separately
(http://docs.sqlalchemy.org/en/latest/orm/mapping_styles.html#classical-mappings),
but the declarative_base style is much more convenient for people who
are mostly going to be using the ORM.
bulk_insert_mappings is part of the ORM layer, so it assumes you are
working with mapped classes. If you just want to insert dictionaries
into a table, you don't need the ORM at all. Something like this ought
to work (using the definitions from your first message):
mytable = metadata.tables['mytable']
session.execute(mytable.insert(), records)
http://docs.sqlalchemy.org/en/latest/core/tutorial.html#executing-multiple-statements
(Note that the Core docs tend to use engines and connections rather
than sessions, because Session is part of the ORM, but
Session.execute() accepts any Core construct)
Hope that helps,
Simon
On Mon, Nov 20, 2017 at 9:16 PM, Skip Montanaro
<skip.montan...@gmail.com> wrote:
> I've narrowed down my problem space a bit. Consider this simple code:
>
> from sqlalchemy import (Integer, String, Column, MetaData, create_engine)
> from sqlalchemy.orm import sessionmaker
> from sqlalchemy.ext.declarative import declarative_base
>
> METADATA = MetaData()
> BASE = declarative_base(metadata=METADATA)
> SESSION = sessionmaker()
>
> class User(BASE):
> __tablename__ = "user"
> first_name = Column(String(32))
> last_name = Column(String(32))
> id = Column(Integer, primary_key=True)
>
> print(type(User))
> print(type(METADATA.tables['user']))
>
> When run, I get this output:
>
> <class 'sqlalchemy.ext.declarative.api.DeclarativeMeta'>
> <class 'sqlalchemy.sql.schema.Table'>
>
> The User class is suitable to use as the first arg to
> session.bulk_insert_mapping(), but the object plucked from the METADATA
> tables dict is not. Will I have to always carry around my own references to
> the various subclasses of BASE which I defined to describe my schema? If I
> have metadata and session objects, is there a way to get back that usable
> (or a usable) class?
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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SQLAlchemy -
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http://www.sqlalchemy.org/
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