I create an API using Lua for query data from MongoDB.
for q_result in q_out:results() do
test_query = "{'a_id': '"..q_result.a_id.."' , 'b_id':'"..bid.."'}"
local rq = assert(db:query('DBName.table', test_query))
Now its order by descending, I find a way to order by ascending.
I see this link but I don't know how to write a parameter.
Suggested way to do this is this:
client.db:query( 'users' , { query={ firstName='Ezra' },
orderby={ lastName=1, firstName=1 } } )
I don't this your query is going to work. You are creating a string and it needs to be a table. Probably something like this:
local test_query = {query = {a_id = q_result.a_id, b_id = bid}}
test_query.orderby = {a_id=1} -- 1 sort ascending, -1 sort descending.
Related
I using Mongo version 4.2
I need to update a field in one collection as based on a field from another collection, according to a joining condiiton between the to collection.
In a regualr SQL, the update would be:
UPDATE col1, col2
SET col2.entityId = col1.Entity_ID
WHERE col1.id = col2.id
and col2.type='DEVICE';
I tried a method offered in one answer, but that does not seem to work, or I did not understand it correctly:
db.col1.find().forEach(function (doc1) {
var doc2 = db.col2.findOne({ id: doc1.id },{type:"DEVICE"});
if (doc2 != null) {
doc1.Entity_ID=doc2.entityId;
db.coll01.save(doc1);
}
});
Any ideas?
Thanks,
Tamar
I am trying to make a complex query in swift to get data from DynamoDB.
I am able to get all information by using the userID. However there are times that I may not know the entirety of the userID and need to make a more complex query.
For instance, if I know the first name and the last name, and the user id format is "firstname:lastname:email", I need to be able to query all userID's that include the first and last name, then add a where for another column.
I am very new to dynamo and want to accomplish something like the sql query below.
SQL example:
SELECT * FROM mytable
WHERE column2 LIKE '%OtherInformation%'
AND (column1 LIKE '%lastname%' OR column1 LIKE '%firstname%')
Here is the code I have in swift4 for getting the userID if I know it exaclty, not entirely sure how to modify this for complex queries.
func queryDBForUser(Fname: String, Lname: String) {
let userId = Fname + "." + Lname + ":" + (UIDevice.current.identifierForVendor?.uuidString)!
self.UserId = userId
let objectMapper = AWSDynamoDBObjectMapper.default()
let queryExpression = AWSDynamoDBQueryExpression()
queryExpression.keyConditionExpression = "#userId = :userId"
queryExpression.expressionAttributeNames = ["#userId": "userId",]
queryExpression.expressionAttributeValues = [":userId": userId,]
objectMapper.query(CheckaraUsers.self, expression: queryExpression, completionHandler: {(response: AWSDynamoDBPaginatedOutput? ,error: Error?) -> Void in
if let error = error {
print("Amazon DynamoDB Error: \(error)")
return
}
I have also tried many variations along the lines of the following code, with no luck:
queryExpression.keyConditionExpression = "#FirstName = :firstName and #LastName = :lastName,"
queryExpression.expressionAttributeNames = ["#FirstName": "FirstName" , "#LastName": "LastName"]
queryExpression.expressionAttributeValues = [":FirstName": Fname,":LastName": Lname]
Any help would be greatly appreciated, thanks in advance!
You won't be able to do this with a DynamoDB query. When you query a table (or index) in DynamoDB you must always specify the complete primary key. In your case that would mean the full value of "firstname:lastname:email".
You could sort of do this with a DynamoDB scan and a filter expression, but that will look at every item in your table, so it could be slow and expensive. Amazon will charge you for the read capacity necessary to look at every item in the table.
So if you really wanted to, the filter expression for the scan operation would be something like:
"contains (#FirstName, :firstName) and contains (#LastName, : lastName)"
Note that contains looks for an exact substring match, so if you want case insensitive matches (like ILIKE in SQL) it won't work.
If you need to do these types of queries then you need to evaluate whether or not DynamoDB is the right choice for you. DynamoDB is a NoSQL key/value store basically. It trades limited querying functionality for scalability and performance. If you are coming at DynamoDB from a SQL background and are expecting to be able to do freeform queries of anything in your table, you will be disappointed.
Got the query working by adding a secondary index to my DynamoDB table, although this is not what I initially wanted, it still works as now I can query for a value that exists in both columns I needed, without doing a table scan and filtering after.
query code:
queryExpression.indexName = "Index-Name" queryExpression.keyConditionExpression = "#LastName = :LastName and #otherValue = :otherValue"
queryExpression.expressionAttributeNames = ["#LastName": "LastName" , "#otherValue": "otherValue"]
queryExpression.expressionAttributeValues = [":LastName": Lname,":otherValue": self.otherValue!]
I have some conditions and a level to check while fetching records from collection using MongoDB.
For this I am using below
def cursorOutput = dataSetCollection.find(whereObject,criteriaObject)
Which is working fine. but I want to use distinct with combination to above query.
def distinctMIdList = dataSetCollection.distinct(hierarchyField,whereObject)
Above is the query for distinct. How to combine two query.
I tried below which is not working
def cursorOutput = dataSetCollection.find(whereObject,criteriaObject).distinct("manager id")
whereObject is a condition to fetch results and criteriaObject is fields to fetch.
Distinct query is giving me result with only Manager id field but I am looking for other field also(use of criteriaObject).
Finally how to combine above two query. I searched for pipeline where $distinct is not available.
Thank you.
Map function:
var mapFunction = function() {
if(/*your criteria*/) {
emit("manager_id", this.manager_id);
}
};
Reduce Function:
var reduceFunction = function(managerFiled,values){
return Array.unique(values);
}
When I use mongo-ruby-driver and I insert new document it returns generated '_id':
db = MongoClient.new('127.0.0.1', '27017').db('ruby-mongo-examples')
id = db['test'].insert({name: 'example'})
# BSON::ObjectId('54f88b01ab8bae12b2000001')
I'm trying to get the '_id' of a document after doing an insertion using Moped:
db = Moped::Session.new(['127.0.0.1:27017'])
db.use('ruby-mongo-examples')
id = db['coll'].insert({name: 'example'})
# {"connectionId"=>15, "n"=>0, "syncMillis"=>0, "writtenTo"=>nil, "err"=>nil, "ok"=>1.0}
How I get the id using Moped?
Update:
I also try use safe mode but it doesn't work:
db = Moped::Session.new(['127.0.0.1:27017'])
db.use('ruby-mongo-examples')
db.with(safe: true) do |safe|
id = safe['coll'].insert({name: 'example'})
# {"connectionId"=>5, "n"=>0, "syncMillis"=>0, "writtenTo"=>nil, "err"=>nil, "ok"=>1.0}
end
After inserting/saving, the returned object will have a property inserted_id which is a BSON::ObjectId:
# I'm using insert_one
result = safe['coll'].insert_one({name: 'example'})
result.methods.sort # see list of methods/properties
result.inserted_id
result.inserted_id.to_s # convert to string
From this issue:
It would be nice, but unfortunately Mongo doesn't give us anything
back when inserting (since it's fire and forget), and when in safe
mode it still doesn't give the id back if it generated it on the
server. So there really isn't any possible way for us to do this
unless it was a core feature in MongoDB.
Your best bet would be to generate the id before inserting the document:
document = { _id: Moped::BSON::ObjectId.new, name: "example" }
id = document[:_id]
I have not clearly issue during query using two criterials like Id and Other. I use a Repository storing some data like id,iso,value. I have created an index("_id","Iso") to performs queries but queries are only returning my cursor if i use only one criterial like _id, but is returning nothing if a use two (_id, Iso) (commented code).
Are the index affecting the response or the query method are failing?
use :v1.6.5 and C# official.
Sample.
//Getting Data
public List<BsonObject> Get_object(string ID, string Iso)
{
using (var helper = BsonHelper.Create())
{
//helper.Db.Repository.EnsureIndex("_Id","Iso");
var query = Query.EQ("_Id", ID);
//if (!String.IsNullOrEmpty(Iso))
// query = Query.And(query, Query.EQ("Iso", Iso));
var cursor = helper.Db.Repository.FindAs<BsonObject>(query);
return cursor.ToList();
}
}
Data:
{
"_id": "2345019",
"Iso": "UK",
"Data": "Some data"
}
After that I have Updated my data using Update.Set() methods. I can see the changed data using MongoView. The new data are correct but the query is always returning the sames olds values. To see these values i use a page that can eventually cached, but if add a timestamp at end are not changing anything, page is always returning the same olds data. Your comments are welcome, thanks.
I do not recall offhand how the C# driver creates indexes, but the shell command for creating an index is like this:
db.things.ensureIndex({j:1});
Notice the '1' which is like saying 'true'.
In your code, you have:
helper.Db.Repository.EnsureIndex("_Id","Iso");
Perhaps it should be:
helper.Db.Repository.EnsureIndex("_Id", 1);
helper.Db.Repository.EnsureIndex("Iso", 1);
It could also be related to the fact that you are creating indexes on "_Id" and the actual id field is called "_id" ... MongoDB is case sensitive.
Have a quick look through the index documentation: http://www.mongodb.org/display/DOCS/Indexes