1
要为代码设置场景,数据库将存储文档,并且每个文档都有可能将图像与它们关联。Node.js异步嵌套mysql查询
我一直在试图编写一个查询数据库的路径,以查找与它们相关的每个文档,将这些数据存储在JSON中,这些数据在完成时返回到ajax请求,因此可以在页面上查看数据。我目前得到的最接近的是下面的尝试(见代码)。
router.post('/advanced_image_search', userAuthenticated, function(req, res, next) {
async.waterfall([
// First function is to get each document which has an image related
function getDocuments(callback){
connection.query(`SELECT DISTINCT(Document.document_id), Document.doc_name, Document.doc_version_no, Document.doc_date_added
FROM Document WHERE doc_type = 'image'`, function(err, results) {
if (err) {
callback(err, null);
return;
}
// The Object containing the array where the data from the db needs to be stored
var documents = {
'docs': []
};
// foreach to iterate through each result found from the first db query (getDocuments)
results.forEach(function(result) {
// New object to store each document
var document = {};
document.entry = result;
// This is the array where each image assciated with a document will be stored
document.entry.images = [];
// Push each document to the array (above)
documents.docs.push(document);
var doc_id = result.document_id;
})
// Returning the results as 'documents' to the next function
callback(null, documents);
})
},
function getImages(documents, callback){
// Variable assignement to the array of documents
var doc_array = documents.docs;
// Foreach of the objects within document array
async.forEachOf(doc_array, function(doc, key, callback){
// Foreach object do the following series of functions
async.waterfall([
function handleImages(callback){
// The id of the document to get the images for
var doc_id = doc.entry.document_id;
connection.query(`SELECT * FROM Image, Document WHERE Image.document_id = '${doc_id}' AND Image.document_id = Document.document_id`, function(err, rows) {
if (err) {
callback(err, null);
return;
}
callback(null, rows);
})
},
// Function below to push each image to the document.entry.images array
//
function pushImages(rows, callback){
// If multiple images are found for that document, the loop iterates through each pushing to the images array
for (var j = 0; j < rows.length; j++) {
// Creating new object for each image found so the data can be stored within this object, then pushed into the images array
var image = {
'image_name': rows[j].image_name
};
doc.entry.images.push(image);
}
callback(null, doc_array);
}
], function(err, doc_array){
if (err) {
console.log('Error in second waterfall callback:')
callback(err);
return;
}
console.log(doc.entry);
// callback(null, doc_array);
})
}, function(err, doc_array){
if (err) {
callback(err);
return;
}
callback(null, doc_array);
});
callback(null, doc_array);
}
], function(err, doc_array) {
if (err){
console.log('Error is: '+err);
return;
}
// The response that should return each document with each related image in the JSON
res.send(doc_array);
})
});
目前返回的结果是:
1:
{entry: {document_id: 1, doc_name: "DocumentNameHere", doc_version_no: 1,…}}
entry:
{document_id: 1, doc_name: "DocumentNameHere", doc_version_no: 1,…}
doc_date_added:"2016-10-24"
doc_name:"DocumentNameHere"
doc_version_no:1
document_id:1
images:[]
以上可以看出,即使与测试中,图像被发现(的console.log)图像阵列保持为空。
我希望有人能够帮助这一点,因为我在努力寻找这一复杂的问题。
谢谢
如果你对此有何评论'//返回结果为“文档”下一个function'你实际上并没有从任何回报功能,但你应该。 – marekful
@marekful我只是做了一个console.log(文件);在下一个函数(getImages())中,所有文档都将返回给它。我认为问题存在于async.forEachOf()的末尾。它似乎没有传递改变的JSON – JRich5