SQLAlchemy-在postgresql中执行批量upsert（如果存在，则更新，否则插入）

Question

sqlalchemy.exc.IntegrityError: (IntegrityError) duplicate key value violates unique constraint "posts_pkey"
DETAIL:  Key (id)=(TEST1234) already exists.

Answer 1

SQLAlchemy中有一个upsert-esque操作：

db.session.merge()

在我找到这个命令后，我能够执行upserts，但值得一提的是，对于批量“upsert”来说，这个操作很慢。

# 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()