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

Posted 2023-03-16

【中文标题】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

【英文标题】：How do I set the dialect for a SQLAlchemy connection pool with PostgreSQL in Django Python? Needed for pre-ping feature enabled

【发布时间】：2021-06-15 17:34:46

【问题描述】：

我正在努力实现的目标

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

错误

当我将pre_ping 属性设置为True 时，我收到以下错误，提示我在使用预ping 功能时需要将dialect 传递给连接池：

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

代码

连接池创建者/处理者的代码：

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

在使用 PostgreSQL 数据库时，如何将这个 dialect 传递到连接池？

其他说明

如果您知道另一种创建连接池并启用了 pre-ping 功能的方法，我们也欢迎您提出这些建议。

谢谢！

【参考方案1】：

QueuePool 构造函数将所有关键字参数传递给 Pool 构造函数。此构造函数支持 dialect 参数。所以你应该可以在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