I want to delete X number of posts starting from the most recently created for a specific user.
How can I apply this logic using mongoose so that I can perform just ONE database operation instead of first having to query for these posts and remove them one by one?
I am finding using the query and projection operators with the $ very confusing, any help would be appreciated.
Below I added pseudo code on how it should to work.
Thank you!
const userId = "123456"
const deleteCount = 6
const deletedPosts = await Post.deleteMany({
.where { userid == userId) }
.sort({createdAt: -1}) // delete by most recent
.limit(deleteCount) // only delete 6 (most recent) posts
}, {new: true}) // return results of operation
console.log(deletedPosts.deletedCount) // -> should be "6"
You can't set a limit when using deleteMany or findAndModify. So, if you want to precisely limit the number of documents removed, you'll need to do it in two steps.
db.getCollection('users').find({}, {class : 4}) .limit(2) .sort({StudentAge: -1}) .toArray() .map(function(doc) { return doc._id; }); //returns the array of id's
db.getCollection('users').deleteMany({_id: {$in: [ "s3", "s4" ]}})//put the array of id's
Related
I am looping through a collection of blog posts to firstly push the username and ID of the blog author to a new array of arrays, and then secondly, count the number of blogs from each author. The code below achieves this; however, in the new array, the username and author ID are no longer separate items in the array, but seem to be concatenated into a single string. I need to retain them as separate items as I need to use both separately; how can I amend the result to achieve this?
var countAuthors = [];
blogAuthors = await Blog.find().populate('authors');
blogAuthors.forEach(function(blogAuthor){
countAuthors.push([blogAuthor.author.username, blogAuthor.author.id]);
})
console.log(countAuthors);
// Outputs as separate array items, as expected:
// [ 'author1', 5d7eed028c298b424b3fb5f1 ],
// [ 'author2', 5dd8aa254d74b30017dbfdd3 ],
var result = {};
countAuthors.forEach(function(x) {
result[x] = (result[x] || 0) + 1;
});
console.log(result);
// Username and author ID become a single string and cannot be accessed as separate array items
// 'author1,5d7eed028c298b424b3fb5f1': 15,
// 'author2,5dd8aa254d74b30017dbfdd3': 2,
Update:
Maybe I can explain a bit further WHY on what to do this. What I am aiming for is a table which displays the blog author's name alongside the number of blogs they have written. However, I also want the author name to link to their profile page, which requires the blogAuthor.author.id to do so. Hence, I need to still be able to access the author username and ID separately after executing the count. Thanks
You could use String.split().
For example:
let result = 'author1,5d7eed028c298b424b3fb5f1'.split(',')
would set result to:
['author1' , '5d7eed028c298b424b3fb5f1']
You can then access them individually like:
result[1] //'5d7eed028c298b424b3fb5f1'
Your issue is that you weren't splitting the x up in the foreach callback, and so the whole array was being converted to a string and being used as the key when inserting into the results object.
You can use array destructuring to split the author name and blog id, and use them to optionally adding a new entry to the result object, and then update that result.
countAuthors = [
['author1', 'bookId1'],
['author2', 'bookId2'],
['author1', 'bookId3'],
['author1', 'bookId4'],
['author2', 'bookId5']
]
var result = {};
countAuthors.forEach(([author, id]) => {
if (result[author] === undefined) {
result[author] = {count: 0, blogIds: []};
}
result[author].count += 1;
result[author].blogIds.push(id);
});
console.log(result);
So I'm a beginner to js and I have a table of users in a json file and I'm making an account delete feature. I have a find set up to find the user and it works fine but I can't figure out how to make it delete the user from the file, any help would be appreciated!
Json:
{
"users": [
{
"name": "ImBattleDash",
"Id": "780748c5d4504446bbba3114ce48f6e9",
"discordId": "471621420162744342",
"dateAdded": 1548295371
}
]
}
JS:
function findJson() {
fs.readFile('./linkedusers.json', 'utf-8', function (err, data) {
if (err) message.channel.send('Invalid Code.')
var arrayOfObjects = JSON.parse(data)
let findEntry = arrayOfObjects.users.find(entry => entry.discordId == myCode)
let linkEmbed = new Discord.RichEmbed()
.setTitle('Account unlinked!')
.setDescription('Link your account by friending "BattleDash Bot" on Fortnite and then input the code you get messaged by typing "!link <code>"!')
.setColor('#a900ff');
message.channel.send({embed: linkEmbed});
})
}
EDIT: Not sure if it's an array or a table I don't know a lot about json
You need to use:
Array#find to find a given user by some given criteria.
Array#indexOf to get the index of the found user in users
Array#splice to drop one element starting from the index given by Array#indexOf:
const input = {
"users": [
{
"name": "ImBattleDash",
"Id": "780748c5d4504446bbba3114ce48f6e9",
"discordId": "471621420162744342",
"dateAdded": 1548295371
}
]
}
const removeUser = (criteria, users) =>
users.splice (users.indexOf (users.find (criteria)), 1)
removeUser (
({ Id, discordId }) =>
Id == '780748c5d4504446bbba3114ce48f6e9'
&& discordId == '471621420162744342',
input.users
)
// Output: 0 <-- User has been removed!
console.log(input.users.length)
About persisting the change, it's just about calling JSON.stringify (input) and then just write the contents to the desired output file. See this other Q&A: Writing files in Node.js
With great help from Cat and Matias I came up with this code that works!
function findJson() {
fs.readFile('./linkedusers.json', 'utf-8', function (err, data) {
if (err) message.channel.send('Invalid Code.')
var arrayOfObjects = JSON.parse(data)
let findEntry = arrayOfObjects.users.find(entry => entry.discordId == myCode)
const input = arrayOfObjects;
const removeUser = (criteria, users) =>
users.splice (users.indexOf (users.find (criteria)), 1)
removeUser (
({ Id, discordId }) =>
Id == findEntry.Id
&& discordId == findEntry.discordId,
input.users
)
console.log('unlinked')
fs.writeFile('./linkedusers.json', JSON.stringify(arrayOfObjects, null, 4), 'utf-8', function(err) {
if (err) throw err
console.log('Done!')
})
let linkEmbed = new Discord.RichEmbed()
.setTitle('Account unlinked!')
.setDescription('Link your account by friending "BattleDash Bot" on Fortnite and then input the code you get messaged by typing "!link <code>"!')
.setColor('#a900ff');
message.channel.send({embed: linkEmbed});
})
}
Here's a quick tutorial for you:
"Users" would be either an array (using []) or a javascript object (using {}), your choice. There won't be any actual tables unless you use a database instead of a JSON file (although if your JSON expression is as simple as your example, you could almost think of it as a table.) -- And actually, a third option would be to use the javascript Map type, which is like a beefed-up object, but I won't address that here.
While using an array would make it a bit easier to retrieve a list of data for all users (because arrays are simpler to iterate through), using an object would make it considerably easier to retrieve data for a single user (since you can directly specify the user you want by its key instead of needing to loop through the whole array until you find the one you want.) I'll show you an example that uses an object.
The individual user in your sample code is an example of a javascript object. JSON lets you convert an object to a string (for storage, I/O, and human readability) and back to an object (so javascript can understand it). You use the JSON.stringify() and JSON.parse() methods, respectively for these conversions. The string has to be JSON-formatted or this won't work, and your example is almost in JSON format.
To comply with JSON formatting, you could structure a Users object as follows. (Of course we're looking at the stringified version because mere humans can't easily read an "actual" javascript object):
"Users": { // Each individual user is a property of your users object
"780748c5d4504446bbba3114ce48f6e9": // The Id is the key in the "key/value pair"
{ // The individual user object itself is the value in the key/value pair
// Id is duplicated inside user for convenience (not necessarily the best way to do it)
"id": "780748c5d4504446bbba3114ce48f6e9",
"name": "ImBattleDash", // Each property of the user is also a key/value pair
"discordId": "471621420162744342", //Commas separate the properties of an object
"dateAdded": "1548295371" // All property values need double quotes for JSON compatibility
}, // Commas separate the properties (ie the individual users) of the users object
"446bbba3114ce48f6e9780748c5d4504": // This string is the second user's key
{ // This object is the second user's value
"id": "446bbba3114ce48f6e9780748c5d4504",
"name": "Wigwam",
"discordId": "162744342471621420",
"dateAdded": "1548295999"
}
}
Once you retrieve the string from storage, you convert it to an object and delete a user as follows. (This is broken down into more steps than necessary for clarity.):
let usersObject = JSON.parse(stringRetrievedFromFile);
let userId = "780748c5d4504446bbba3114ce48f6e9";
let userToModifyOrDelete = usersObject[userId];
delete userToModifyOrDelete;
To change the user's discordId instead, you would do:
let discordId = userToModifyOrDelete.discordId; // Not necessary, just shows how to retrieve value
let newDiscordId = "whateverId";
userToModifyOrDelete.discordId = newDiscordId;
And you'd convert the object back into a string to store in your file with:
JSON.stringify(usersObject);
Hopefully that's almost all you need to know about JSON!
I have JSON data by which i am creating nodes and relationship between nodes using https://github.com/thingdom/node-neo4j connector.
I have following JSON format
{
att0:"abcd",
att1:"val1",
att2:"val2",
att3:"val3",
att4:"val4",
att5:"val5",
att6:"val6",
att7:"val7",
att8:"val8"
} .... more like this around 1000
Here att0+att1 gives me unique id after md5 hash (let it be UID1) .
and att4 gives me unique id after md5 hash (let it be UID2).
and att7 gives me unique id after md5 hash (let it be UID3).
I am creating two node of following properties :
Node 1 :
{
id: UID1 ,
att3:"val3"
}
Node 2 :
{
id:UID2,
att5:"val5",
att6:"val6"
}
Relationship from Node 1 --> Node 2 :
{
id:UID3,
att5:"val8"
}
Following is my data insertion query:
for(i=0; i<1000; i++){ // 1000 objects in json
// create UID1,UID2 and UID3 based on above info for each object
// and create query string as mentioned below
query_string = MERGE (n:nodes_type1 {id:'UID1'})
ON CREATE SET n={ id:'UID1', att3:'val3'},n.count=1
ON MATCH SET n.count = n.count +1
MERGE (m:nodes_type2 {id:'UID2'})
ON CREATE SET m={ id:'UID2', att5:'val5', att6:'val6'},m.count=1
ON MATCH SET m.count = m.count +1
MERGE (n)-[x:relation_type {id:'UID3'} ]->(m)
ON CREATE SET x={ att8:'val8', id:'UID3' },x.count=1
ON MATCH SET x.count = x.count +1 return n
db.query(query_string, params, function (err, results) {
if (err) {
console.log(err);
throw err;
}
console.log("Node Created !!! "+ event_val)
});
}
Firstly i cleared my neo4j database using following query externally ( using neo4j database UI):
Now problem is when i query MATCH (n:nodes_type2) return COUNT(n). Since there are 1000 objects in json it should create 1000 nodes.But the result is coming more than 1000 (around 9000) and keeps on changing as every time when i clear the data and restart the script. When i saw in the results there were multiple nodes of the same UID . Shouldn't merge query handel node match and increment counter . Merge is incrementing the counter but after some number, new node is created with same UID.
Based on your given query, I assume the UUID generated looks to be different on each loop :
1000 loops, 3 queries with 3 different node labels.
Can you count distinct uuids you get from your database, like :
MATCH (n) RETURN count(DISTINCT n.id)
I assue your queries are executed massively in parallel,
make sure to have a unique constraint for : nodes_type1(id) and nodes_type2(id) installed, otherwise MERGE cannot guarantee uniqueness.
Also you should change your query to use parameters instead of literal values
And it should also look like this:
MERGE (n:nodes_type1 {id:{id1}})
ON CREATE SET n.att3={att3},n.count=1
ON MATCH SET n.count = n.count +1
MERGE (m:nodes_type2 {id:{id2}})
ON CREATE SET m.att5={att5}, m.att6={att6},m.count=1
ON MATCH SET m.count = m.count +1
MERGE (n)-[x:relation_type {id:{id3}} ]->(m)
ON CREATE SET x.att8={att8},x.count=1
ON MATCH SET x.count = x.count+1
return n,r,m
I don't think the id and counter on the relationship make sense in a real use-case but for your test it might be ok
I have store with multiEntry index on tags.
{ tags: [ 'tag1', 'tag2', 'tag3' ] }
And i have query that also list of tags.
[ 'tag2', 'tag1', 'tag4' ]
I need to get all records which contain one of tag in query (Similar to SQL OR statement).
Currently I cannot find any other solution except iterate over tags in query and search by the each tag in the store.
Is there any better solution?
Thank you.
You cannot retrieve all results with one query except with iteration. You can optimize the search result by opening a index from the lowest value to the highest:
IDBKeyRange.bound ('tag1', 'tag4');
Other Indexed-Db feature you can use is to open multiple queries and combine the result when the queries complete. This way would be much faster than the iteration.
IndexedDB has only range query as Deni Mf answered.
OR query is simply union of multiple queries. That may be OK.
If you want efficient query, you have to iterate the cursor and seek the cursor position as necessary. Using my library, it will be
tags = ['tag2', 'tag1', 'tag4'];
tags.sort();
iter = new ydn.db.KeyIterator('store name', 'tags', IDBKeyRange.bound(tags[0], tags[tags.length-1]);
keys = [];
i = 0;
var req = db.open(iter, function(cursor) {
if (tags.indexOf(cursor.indexKey()) >= 0) {
// we got the result
if (keys.indexOf(cursor.key()) == -1) { // remove duplicate
keys.push(cursor.key());
}
} else {
return tags[++i]; // jump to next index position.
}
);
req.done(function() {
db.list('store name', keys).done(function(results) {
console.log(results);
}
});
Notice that the algorithm has no false positive retrieval. Key only query is performed first, so that we don't waste on de-serilization. The results is retrieved only we get all the primary keys after removing deplicates.
Given these documents:
db.orders.insert( {OrderId:1, OrderItems: [{OrderItemId:1, Qty:1}, {OrderItemId:2, Qty:1} ]} );
db.orders.insert( {OrderId:2, OrderItems: [{OrderItemId:1, Qty:1}, {OrderItemId:2, Qty:2} ]} );
I'd like to get the count of all OrderItems where the Qty = 1 (expected result 3). This is how I think to write the query, but it returns 2 (1 for each Order document):
db.orders.find({"OrderItems.Qty":1}).count();
How can I query to find the count of all OrderItems where the Qty = 1?
Just to be clear for others reading this thread.
The OP's command db.orders.find({"OrderItems.Qty":1}).count(); basically counts the number of Documents where any order item has a quantity of 1.
However, the OP wants a count of all OrderItems where the quantity is one. The problem here is that we're not counting Documents. We're counting items within an array within a Document. Hence the need for javascript and some form of special reduce operation.
You could use JavaScript:
db.orders.group(
{
key: null,
cond: {'OrderItems.Qty':1},
initial: {count: 0},
reduce: function(el, running)
{
running.count += el.OrderItems.filter(function(el)
{
return el.Qty == 1;
}).length;
}
});
This should do it for you in the shell without JavaScript (so it'll be a lot quicker);
db.orders.aggregate([
{$unwind:'$OrderItems'},
{$match: {'OrderItems.Qty':1}},
{$group : {
_id : "Qty1",
sum: {$sum:1}
}}
]);
Although it's unfortunate your data is structured like that if this is a common query. Having to do an $unwind is relatively expensive. It's a shame your order items aren't laid out as separate documents tagged with the order ID instead of orderID documents containing arrays of order items...in other words, the reverse of what you have. That would be much easier and more efficient to process.
db.orders.aggregate([
{$unwind: '#OrderItems'},
{$match : {'OrderItems.Qty':1}},
{$group : { _id : null, 'countOfQty1':{$sum:'$OrderItems.Qty'} }}
]);