背景：数据库某张表定时有第三方更新到实时表里，收到数据更新以后，WEBSOCKET发送前端
-- 创建一个发送通知的函数
CREATE OR REPLACE FUNCTION notify_event(event_name text) RETURNS void AS $$
BEGIN
PERFORM pg_notify(event_name, '');
END;
$$ LANGUAGE plpgsql;
-- 创建一个触发器，在数据变化时调用通知函数
CREATE OR REPLACE FUNCTION notify_trigger() RETURNS trigger AS $$
BEGIN
PERFORM notify_event('data_changed');
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
-- 在需要监听的表上创建触发器
CREATE TRIGGER data_change_trigger
AFTER INSERT OR UPDATE OR DELETE ON river_area
FOR EACH ROW
EXECUTE FUNCTION notify_trigger();
.net core创建一个后台运行服务
using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Npgsql;
namespace Pipe.BLL
{
public class TableUpdateListenerService : BackgroundService
{
private readonly IServiceProvider _services;
public TableUpdateListenerService(IServiceProvider services)
{
_services = services;
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
using var scope = _services.CreateScope();
var serviceProvider = scope.ServiceProvider;
var connectionString = serviceProvider.GetRequiredService<IConfiguration>().GetConnectionString("LocalNpgsqlConnection");
using var conn = new NpgsqlConnection(connectionString);
await conn.OpenAsync(stoppingToken);
using var cmd = new NpgsqlCommand("listen data_changed", conn);
cmd.ExecuteNonQuery();
conn.Notification += (sender, e) =>
{
Console.WriteLine($"Received table update notification: {e.Payload}");
// 在这里执行相应的操作，处理接收到的通知
};
while (!stoppingToken.IsCancellationRequested)
{
using var transaction = conn.BeginTransaction();
await transaction.CommitAsync();
await Task.Delay(TimeSpan.FromSeconds(1), stoppingToken); // 可以选择适当的延迟时间
}
}
}
}
startup.cs注册下服务 services.AddHostedService<TableUpdateListenerService>();
psql 发送测试。
UPDATE "public"."river_area" SET "objectid" = 5 WHERE "gid" = 3;
NOTIFY data_changed, 'Your notification payload here'; 测试通过