使用节点对mongodb进行多次查询
本文关键字：查询 mongodb 节点 | 更新日期: 2023-09-27 18:02:03
我似乎找不到一个合适的答案来回答我的问题，我已经看遍了stackoverflow。考虑一下c#中的示例代码，我试图将其移植到nodejs + mongobd。
var messageList = new List<MessageHelper>();
foreach( MessageActivation messageToAsk in messagesToAsk )
{
var message = from m in dbContext.Messages where m.Id == messageToAsk.MessageId select m;
var jokeMessage = from m in dbContext.Messages where m.Id == messageToAsk.JokeMessageId select m;
var user = from u in dbContext.Users where u.Id == messageToAsk.SourceUserId select u;
var messageHelper = new MessageHelper();
messageHelper.AskingUserId = user.ToList()[0].Id;
messageHelper.Message = message.ToList()[0];
messageList.Add( messageHelper );
}
return messageList;
用node的方式做这个最好的方法是什么?dbContext只是一个侧节点，它将查询数据库。关键是收集所有需要的信息，打包，然后再发送。
感谢编辑:这是我尝试过的
// collect needed info to make next queries in db
var messageIdList = new Array();
var jokeMessageIdList = new Array();
var sourceUserIdList = new Array();
for( var i=0; i < messagesToAsk.length; i++ )
{
messageIdList.push( messagesToAsk[i].MessageId );
jokeMessageIdList.push( jokeMessageId[i].JokeMessageId );
sourceUserIdList .push( jokeMessageId[i].SourceUserId );
}
// make requests to have all the data in place
var messages = App.DataModels.Messages.find( {} );
messages.where( 'MessageId' ).in( messageIdList );
messages.exec( function ( err, foundMessages )
{
var jokeMessages = App.DataModels.Messages.find( {} );
jokeMessages.where( 'JokeMessageId' ).in( jokeMessageIdList );
jokeMessages.exec( function ( err, foundJokeMessages )
{
var users = App.DataModels.Messages.find( {} );
users.where( 'SourceUserId' ).in( sourceUserIdList );
users.exec( function ( err, foundUsers )
{
var messageList = new Array(); // new List<MessageHelper>();
for( var i=0; i < messagesToAsk.length; i++ )
{
var message = null;
var jokeMessage = null;
var user = null;
// get the data
for( var j = 0; j < messages.length; j++ )
{
if( messages[j].MessageId === messagesToAsk[i].MessageId )
{
message = messages[j];
break;
}
}
for( var k = 0; k < jokeMessages.length; k++ )
{
if( jokeMessages[k].JokeMessageId === messagesToAsk[k].JokeMessageId )
{
jokeMessage = jokeMessage[k];
break;
}
}
for( var l = 0; l < users.length; l++ )
{
if ( users[l].SourceUserId === messagesToAsk[l].SourceUserId )
{
user = users[l];
break;
}
}
var messageHelper =
{
"AskingUserId" : user.Id,
"AskingUserPic" : user.HelperPhoto,
"Message" : message,
"JokeMessage" : message.Type === "1" ? jokeMessage.Content
};
messageList.Add( messageHelper );
}
responseDelegate( response, messageList );
});
});
});
我把它贴在这里是为了其他一些正在转变的人。这个想法似乎是，在开始迭代和组装任何最终结果发送之前，您需要已经收集和过滤了所有数据。
在将c#/Linq DB查询类比到NodeJS/Mongo的背景下回答我的问题。一种映射的"思维"方式。这主要是为了理解这种转变。一个正确的实现应该是使用像Promise/deferred这样的模式(库)，就像@WiredPrairie对这个问题的评论中建议的那样。
// collect needed info to make next queries in db
var messageIdList = new Array();
var jokeMessageIdList = new Array();
var sourceUserIdList = new Array();
for( var i=0; i < messagesToAsk.length; i++ )
{
messageIdList.push( messagesToAsk[i].MessageId );
jokeMessageIdList.push( jokeMessageId[i].JokeMessageId );
sourceUserIdList .push( jokeMessageId[i].SourceUserId );
}
// make requests to have all the data in place
var messages = App.DataModels.Messages.find( {} );
messages.where( 'MessageId' ).in( messageIdList );
messages.exec( function ( err, foundMessages )
{
var jokeMessages = App.DataModels.Messages.find( {} );
jokeMessages.where( 'JokeMessageId' ).in( jokeMessageIdList );
jokeMessages.exec( function ( err, foundJokeMessages )
{
var users = App.DataModels.Messages.find( {} );
users.where( 'SourceUserId' ).in( sourceUserIdList );
users.exec( function ( err, foundUsers )
{
var messageList = new Array(); // new List<MessageHelper>();
for( var i=0; i < messagesToAsk.length; i++ )
{
var message = null;
var jokeMessage = null;
var user = null;
// get the data
for( var j = 0; j < messages.length; j++ )
{
if( messages[j].MessageId === messagesToAsk[i].MessageId )
{
message = messages[j];
break;
}
}
for( var k = 0; k < jokeMessages.length; k++ )
{
if( jokeMessages[k].JokeMessageId === messagesToAsk[k].JokeMessageId )
{
jokeMessage = jokeMessage[k];
break;
}
}
for( var l = 0; l < users.length; l++ )
{
if ( users[l].SourceUserId === messagesToAsk[l].SourceUserId )
{
user = users[l];
break;
}
}
var messageHelper =
{
"AskingUserId" : user.Id,
"AskingUserPic" : user.HelperPhoto,
"Message" : message,
"JokeMessage" : message.Type === "1" ? jokeMessage.Content
};
messageList.Add( messageHelper );
}
responseDelegate( response, messageList );
});
});
});