如何使用Python在 PostgreSQL 中记录查询？

Python有各种用于 PostgreSQL 的数据库驱动程序。当前最常用的版本是 psycopg2。它完全实现了Python DB-API 2.0 规范。 psycopg2 提供了许多有用的功能，例如客户端和服务器端游标、异步通知和通信、COPY 命令支持等。

安装

安装 psycopg2 模块：

pip install psycopg2

为了记录有关命令的信息，我们需要安装 logtopg：

pip install logtopg

应用

• 信息收集
• 故障排除
• 生成统计信息
• 审计
• 剖析

日志级别及其目的

Level	Purpose
DEBUG	Detailed information, typically of interest only when diagnosing problems.
INFO	Confirmation that things are working as expected.
WARNING	An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected.
ERROR	Due to a more serious problem, the software has not been able to perform some function.
CRITICAL	A serious error, indicating that the program itself may be unable to continue running.

所有记录器都是根记录器的后代。根记录器始终具有明确的级别集，默认情况下为 WARNING。根记录器可用于轻松打开和关闭所有库中的所有记录器。

记录器信息显示

Level	Display
debug	Should only appear in the file
info	Should appear in file
warning	Should appear in file and stdout
error	Should appear in file and stdout
critical	Should appear in file and stdout

为了更好地理解日志，这里有一个简单的代码，没有连接到 PostgreSQL，它只在控制台中显示消息。

例子：

Python3

import logging
  
# This will be printed only in file
logging.debug('This is a debug message')
  
# This will be printed only in file
logging.info('This is an info message')
  
logging.warning('This is a warning message')
logging.error('This is an error message')
logging.critical('This is a critical message')

输出：

使用了根记录器，只写入了三条消息。这是因为默认情况下，只写入级别警告和级别更高的消息。

下面给出了另一个理解日志级别的例子。日志级别由 setLevel() 设置。

示例 1：

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import logging
  
# The getLogger() returns a logger with the specified name.
# If name is None, it returns the root logger.
logger = logging.getLogger('dev')
  
# Level is set
logger.setLevel(logging.DEBUG)
  
logger.debug('This is a debug message')
logger.info('This is an info message')
logger.warning('This is a warning message via setLevel')
logger.error('This is an error message via setLevel')
logger.critical('This is a critical message via setLevel')

输出 ：

getLogger 和 setLevel

示例 2：

“mylib.py”应该在“sample.py”所在的同一目录中，并且创建的文件“myapp.log”将出现在mylib.py和sample.py所在的同一目录中

mylib.py

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#Let this program name be mylib.py
import logging
  
def from_mylib():
    logging.info('I am from mylib')

让我们在另一个代码中使用 mylib.py

样本.py

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#logging module is required to log information
import logging
  
# User created python code and should be in same directory
import mylib
  
def main():
  
    # As we have specified myapp.log, all log information will be there
    # logging.INFO is the level, it will get printed
    logging.basicConfig(filename='myapp.log', level=logging.INFO)
    logging.info('Started to print logger info')
      
    # calling mylib method here as have imported. It should be
    # in same directory
    mylib.from_mylib()
    logging.info('Finished logging the information!!!')
  
# Main code
if __name__ == '__main__':
    main()

myapp.log 的输出（在 mylib.py 和 sample.py 所在的同一目录中创建）存在

myapp.log 内容

示例 3：

此示例讨论与 PostgreSQL 与数据库的交互。 pgAdmin 或 psql 是可用于登录 PostgreSQL 数据库服务器的客户端工具。

数据库名称：testdb

表名：员工

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import logging
import psycopg2
from psycopg2.extras import LoggingConnection
  
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger("loggerinformation")
  
# We need to specify the necessary parameters in the below list
# As connecting with postgres/password as username/password and with testdb as parameters
db_settings = {
    "user": "postgres",
    "password": "password",
    "host": "127.0.0.1",
    "database": "testdb",
}
  
# connect to the PostgreSQL server
conn = psycopg2.connect(connection_factory=LoggingConnection, **db_settings)
conn.initialize(logger)
  
cur = conn.cursor()
cur.execute("SELECT * FROM employee")

输出 ：

示例 4：

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import logging
import psycopg2
from psycopg2.extras import LoggingConnection
  
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger("loggerinformation")
  
db_settings = {
    "user": "postgres",
    "password": "password",
    "host": "127.0.0.1",
    "database": "testdb",
}
  
conn = psycopg2.connect(connection_factory=LoggingConnection, **db_settings)
conn.initialize(logger)
  
cur = conn.cursor()
cur.execute("SELECT * FROM employee")
  
# insert records in employee table
cur.execute(
    "INSERT INTO employee (first_name,last_name,age,gender,income) VALUES ('123','456',20,'m',20000)")

输出：

选择并插入查询日志