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Modelling UPSERT in SQLAlchemy (well actually it is not upsert but speed improvement is significant in comparison with simple session.merge)
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| # Note: it is a copy of great answer by "mgoldwasser" from Stackoverflow | |
| # Check the original answer here: http://stackoverflow.com/a/26018934/1032439 | |
| # Imagine that post1, post5, and post1000 are posts objects with ids 1, 5 and 1000 respectively | |
| # The goal is to "upsert" these posts. | |
| # we initialize a dict which maps id to the post object | |
| my_new_posts = {1: post1, 5: post5, 1000: post1000} | |
| for each in posts.query.filter(posts.id.in_(my_new_posts.keys())).all(): | |
| # Only merge those posts which already exist in the database | |
| db.session.merge(my_new_posts.pop(each.id)) | |
| # Only add those posts which did not exist in the database | |
| db.session.add_all(my_new_posts.values()) | |
| # Now we commit our modifications (merges) and inserts (adds) to the database! | |
| db.session.commit() |
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Thanks!