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Added additional documentation to MatematDatabase.

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s3lph 2018-06-06 14:13:42 +02:00
parent 8eda31cbbe
commit 7a8c898ebc
1 changed files with 10 additions and 2 deletions
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12
matemat/db/facade.py
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@ -328,10 +328,11 @@ class MatematDatabase(object):
the statistics table. the statistics table.
:param user: The user buying a product. :param user: The user buying a product.
:param product: The product the user is buying. :param product: The product the user is buying.
:param count: How many instances of the product the user is buying, defaults to 1. :param count: How many units of the product the user is buying, defaults to 1.
:raises DatabaseConsistencyError: If the user or the product does not exist in the database. :raises DatabaseConsistencyError: If the user or the product does not exist in the database.
""" """
with self.db.transaction() as c: with self.db.transaction() as c:
# Retrieve the consumption entry for the (user, product) pair, if any.
c.execute(''' c.execute('''
SELECT count SELECT count
FROM consumption FROM consumption
@ -343,6 +344,7 @@ class MatematDatabase(object):
}) })
row = c.fetchone() row = c.fetchone()
if row is None: if row is None:
# If the entry does not exist, create a new one.
c.execute(''' c.execute('''
INSERT INTO consumption (user_id, product_id, count) INSERT INTO consumption (user_id, product_id, count)
VALUES (:user_id, :product_id, :count) VALUES (:user_id, :product_id, :count)
@ -352,6 +354,7 @@ class MatematDatabase(object):
'count': count 'count': count
}) })
else: else:
# If the entry exists, update the consumption count.
c.execute(''' c.execute('''
UPDATE consumption UPDATE consumption
SET count = count + :count SET count = count + :count
@ -361,10 +364,12 @@ class MatematDatabase(object):
'product_id': product.id, 'product_id': product.id,
'count': count 'count': count
}) })
# Make sure exactly one consumption row was updated/inserted.
affected = c.execute('SELECT changes()').fetchone()[0] affected = c.execute('SELECT changes()').fetchone()[0]
if affected != 1: if affected != 1:
raise DatabaseConsistencyError( raise DatabaseConsistencyError(
f'increment_consumption should affect 1 consumption row, but affected {affected}') f'increment_consumption should affect 1 consumption row, but affected {affected}')
# Compute the cost of the transaction and subtract it from the user's account balance.
c.execute(''' c.execute('''
UPDATE users UPDATE users
SET balance = balance - :cost SET balance = balance - :cost
@ -372,10 +377,12 @@ class MatematDatabase(object):
'user_id': user.id, 'user_id': user.id,
'cost': count * product.price_member if user.is_member else count * product.price_non_member 'cost': count * product.price_member if user.is_member else count * product.price_non_member
}) })
# Make sure exactly one user row was updated.
affected = c.execute('SELECT changes()').fetchone()[0] affected = c.execute('SELECT changes()').fetchone()[0]
if affected != 1: if affected != 1:
raise DatabaseConsistencyError( raise DatabaseConsistencyError(
f'increment_consumption should affect 1 users row, but affected {affected}') f'increment_consumption should affect 1 users row, but affected {affected}')
# Subtract the number of purchased units from the product's stock.
c.execute(''' c.execute('''
UPDATE products UPDATE products
SET stock = stock - :count SET stock = stock - :count
@ -384,6 +391,7 @@ class MatematDatabase(object):
'product_id': product.id, 'product_id': product.id,
'count': count 'count': count
}) })
# Make sure exactly one product row was updated.
affected = c.execute('SELECT changes()').fetchone()[0] affected = c.execute('SELECT changes()').fetchone()[0]
if affected != 1: if affected != 1:
raise DatabaseConsistencyError( raise DatabaseConsistencyError(
@ -393,7 +401,7 @@ class MatematDatabase(object):
""" """
Update the stock of a product. Update the stock of a product.
:param product: The product to restock. :param product: The product to restock.
:param count: Number of instances of the product to add. :param count: Number of units of the product to add.
:raises DatabaseConsistencyError: If the product represented by the object does not exist. :raises DatabaseConsistencyError: If the product represented by the object does not exist.
""" """
with self.db.transaction() as c: with self.db.transaction() as c: