如何在 Django Python 中使用 PostgreSQL 为 SQLAlchemy 连接池设置方言？需要启用预 ping 功能

Question

我想要实现的目标

我需要为 Django 中的 SQLAlchemy 数据库池激活预 ping 功能 Python。

错误

当我将 pre_ping 属性 设置为 True 时，出现以下错误，提示我在使用预 ping 功能：

The ping feature requires that a dialect is passed to the connection pool.

代码

连接池代码creator/handler:

import psycopg2
from sqlalchemy import create_engine
import traceback
from myproject import settings
from dataClasses.EmptyObject import *
import json
import sqlalchemy.pool as pool
from sqlalchemy.pool import QueuePool

dbPool = None

class DbPoolHelper:

    def ensurePoolCreated(self):
        global dbPool
        if dbPool != None:
            return
            
        self.createPool()

    def dbConnect(self):
        dbConfig = self.getDbPoolConfig()
        dbConnection = psycopg2.connect(user=dbConfig.user, password=dbConfig.password, dbname=dbConfig.dbName, host=dbConfig.host, port=dbConfig.port)
        print("=========== POOL CONNECTED =================")
        return dbConnection

    def createPool(self):
        dbConnection = self.dbConnect
        global dbPool
        dbPool = pool.QueuePool(dbConnection, max_overflow=10, pool_size=5, pre_ping=True)
        print("=========== POOL CREATED =================")

    def execute(self, sql, sqlParams):
        try:
            global dbPool
            self.ensurePoolCreated()
            poolConnection = dbPool.connect()
            cursor = poolConnection.cursor()
            cursor.execute(sql, sqlParams)
            poolConnection.commit()
            result = cursor.fetchall()
            cursor.close()
            poolConnection.close()
            return result
        except Exception as e:
            print(e)
            return e

    def getDbPoolConfig(self):
        settingName = "pool"
        dbConfig = EmptyObject()
        dbConfig.host = settings.DATABASES[settingName]["HOST"]
        dbConfig.port = settings.DATABASES[settingName]["PORT"]
        dbConfig.user = settings.DATABASES[settingName]["USER"]
        dbConfig.password = settings.DATABASES[settingName]["PASSWORD"]
        dbConfig.dbName = settings.DATABASES[settingName]["NAME"]
        dbConfig.poolSize = settings.DATABASES[settingName]["POOL_SIZE"]
        dbConfig.poolMaxOverflow = settings.DATABASES[settingName]["POOL_MAX_OVERFLOW"]
        dbConfig.poolRecycleTime = settings.DATABASES[settingName]["POOL_RECYCLE_TIME"]

        return dbConfig

问题

如何在使用 PostgreSQL 数据库时将此 dialect 传递给连接池？

其他说明

如果您知道另一种在启用预 ping 功能的情况下创建连接池的方法，也欢迎这些建议。

谢谢！

Answer 1

QueuePool constructor passes all keyword arguments to the Pool 构造函数。此构造函数支持 dialect 参数。所以你应该能够在你的 QueuePool 通话中添加方言：

from sqlalchemy.dialects import postgresql
# redacted
dbPool = pool.QueuePool(dbConnection, max_overflow=10, pool_size=5, pre_ping=True, dialect=postgresql.dialect())
# redacted