实现涉及多个 PostgreSQL 语句(包括错误处理)的示例事务。另外,演示分布式环境中事务和回滚的使用。
完成实施流程并提供示例(如果可能)。
下面是一个组合示例,涉及具有多个 PostgreSQL 语句的分布式事务,包括错误处理。此示例假设有两个数据库,database1 和 database2,并演示了它们之间的协调事务。
import psycopg2
from psycopg2 import sql
# Connection parameters for database1
db1_params = {
'dbname': 'database1',
'user': 'user1',
'password': 'password1',
'host': 'host1',
'port': 'port1'
}
# Connection parameters for database2
db2_params = {
'dbname': 'database2',
'user': 'user2',
'password': 'password2',
'host': 'host2',
'port': 'port2'
}
def insert_user_and_related_data():
try:
# Start the distributed transaction
conn1.autocommit = False
conn2.autocommit = False
# Insert a new user into database1
insert_user_db1 = sql.SQL("INSERT INTO users (username, email) VALUES ({}, {}) RETURNING id").format(
sql.Literal("john_doe_db1"),
sql.Literal("[email protected]")
)
cursor1.execute(insert_user_db1)
user_id_db1 = cursor1.fetchone()[0]
# Insert a related record into database2
insert_related_data_db2 = sql.SQL("INSERT INTO related_data (user_id, data) VALUES ({}, {})").format(
sql.Literal(user_id_db1),
sql.Literal("some_data_db2")
)
cursor2.execute(insert_related_data_db2)
except psycopg2.DatabaseError as e:
# Handle the error
print(f"Error: {e}")
conn1.rollback() # Rollback transaction on database1
conn2.rollback() # Rollback transaction on database2
raise # Re-raise the exception
else:
# Commit the distributed transaction if there are no errors
conn1.commit()
conn2.commit()
print(f"Distributed transaction committed successfully. User ID: {user_id_db1}")
finally:
# Close cursors and connections
cursor1.close()
conn1.close()
cursor2.close()
conn2.close()
# Create connections and cursors for both databases
conn1 = psycopg2.connect(**db1_params)
cursor1 = conn1.cursor()
conn2 = psycopg2.connect(**db2_params)
cursor2 = conn2.cursor()
# Execute the distributed transaction
insert_user_and_related_data()