I'm trying to perform an update in Amazon DynamoDB, but only if a StringSet does not contain a specific string. Looking at the AWS docs I saw that there exists the contains() function, which can be used inside the ConditionExpression. Then I tried this code:
function addLecture(event){
const params = {
TableName: 'lectures',
Key: {
'lecture_id': Number.parseInt(event.lecture_id)
},
UpdateExpression: 'SET numeric_attr = numeric_attr - :val ADD students :student',
ConditionExpression: '(numeric_attr > :limit) AND (NOT contains(students, :student))',
ExpressionAttributeValues: {
':val': 1,
':limit' : 0,
':student' : ddb.createSet(event.student)
},
ReturnValues : 'UPDATED_NEW'
}
return ddb.update(params).promise();
}
Anyway, if I try to perform the update, it is actually performed, even if the String is already in the StringSet.
How could I check for the absence of the String?
I think your condition is malformated:
:student resolves to ddb.createSet(event.student). You should pass a string variable to contains, and not a string set. From the doc you pointed out:
The operand must be a String if the attribute specified by path is a String. If the attribute specified by path is a Set, the operand must be the set's element type.
In a Cosmos DB stored procedure, I'm using a inline sql query to try and retrieve the distinct count of a particular user id.
I'm using the SQL API for my account. I've run the below query in Query Explorer in my Cosmos DB account and I know that I should get a count of 10 (There are 10 unique user ids in my collection):
SELECT VALUE COUNT(1) FROM (SELECT DISTINCT c.UserId FROM root c) AS t
However when I run this in the Stored Procedure portal, I either get 0 records back or 18 records back (total number of documents). The code for my Stored Procedure is as follows:
function GetDistinctCount() {
var collection = getContext().getCollection();
var isAccepted = collection.queryDocuments(
collection.getSelfLink(),
'SELECT VALUE COUNT(1) FROM (SELECT DISTINCT c.UserId FROM root c) AS t',
function(err, feed, options) {
if (err) throw err;
if (!feed || !feed.length) {
var response = getContext().getResponse();
var body = {code: 404, body: "no docs found"}
response.setBody(JSON.stringify(body));
} else {
var response = getContext().getResponse();
var body = {code: 200, body: feed[0]}
response.setBody(JSON.stringify(body));
}
}
)
}
After looking at various feedback forums and documentation, I don't think there's an elegant solution for me to do this as simply as it would be in normal SQL.
the UserId is my partition key which I'm passing through in my C# code and when I test it in the portal, so there's no additional parameters that I need to set when calling the Stored Proc. I'm calling this Stored Proc via C# and adding any further parameters will have an effect on my tests for that code, so I'm keen not to introduce any parameters if I can.
Your problem is caused by that you missed setting partition key for your stored procedure.
Please see the statements in the official document:
And this:
So,when you execute a stored procedure under a partitioned collection, you need to pass the partition key param. It's necessary! (Also this case explained this:Documentdb stored proc cross partition query)
Back to your question,you never pass any partition key, equals you pass an null value or "" value for partition key, so it outputs no data because you don't have any userId equals null or "".
My advice:
You could use normal Query SDK to execute your sql, and set the enableCrossPartitionQuery: true which allows you scan entire collection without setting partition key. Please refer to this tiny sample:Can't get simple CosmosDB query to work via Node.js - but works fine via Azure's Query Explorer
So I found a solution that returns the result I need. My stored procedure now looks like this:
function GetPaymentCount() {
var collection = getContext().getCollection();
var isAccepted = collection.queryDocuments(
collection.getSelfLink(),
'SELECT DISTINCT VALUE(doc.UserId) from root doc' ,
{pageSize:-1 },
function(err, feed, options) {
if (err) throw err;
if (!feed || !feed.length) {
var response = getContext().getResponse();
var body = {code: 404, body: "no docs found"}
response.setBody(JSON.stringify(body));
} else {
var response = getContext().getResponse();
var body = {code: 200, body: JSON.stringify(feed.length)}
response.setBody(JSON.stringify(body));
}
}
)
}
Essentially, I changed the pageSize parameter to -1 which returned all the documents I knew would be returned in the result. I have a feeling that this will be more expensive in terms of RU/s cost, but it solves my case for now.
If anyone has more efficient alternatives, please comment and let me know.
From the docs:
You can also chain multiple where() methods to create more specific queries (logical AND).
How can I perform an OR query?
Example:
Give me all documents where the field status is open OR upcoming
Give me all documents where the field status == open OR createdAt <= <somedatetime>
OR isn't supported as it's hard for the server to scale it (requires keeping state to dedup). The work around is to issue 2 queries, one for each condition, and dedup on the client.
Edit (Nov 2019):
Cloud Firestore now supports IN queries which are a limited type of OR query.
For the example above you could do:
// Get all documents in 'foo' where status is open or upcmoming
db.collection('foo').where('status','in',['open','upcoming']).get()
However it's still not possible to do a general OR condition involving multiple fields.
With the recent addition of IN queries, Firestore supports "up to 10 equality clauses on the same field with a logical OR"
A possible solution to (1) would be:
documents.where('status', 'in', ['open', 'upcoming']);
See Firebase Guides: Query Operators | in and array-contains-any
suggest to give value for status as well.
ex.
{ name: "a", statusValue = 10, status = 'open' }
{ name: "b", statusValue = 20, status = 'upcoming'}
{ name: "c", statusValue = 30, status = 'close'}
you can query by ref.where('statusValue', '<=', 20) then both 'a' and 'b' will found.
this can save your query cost and performance.
btw, it is not fix all case.
I would have no "status" field, but status related fields, updating them to true or false based on request, like
{ name: "a", status_open: true, status_upcoming: false, status_closed: false}
However, check Firebase Cloud Functions. You could have a function listening status changes, updating status related properties like
{ name: "a", status: "open", status_open: true, status_upcoming: false, status_closed: false}
one or the other, your query could be just
...where('status_open','==',true)...
Hope it helps.
This doesn't solve all cases, but for "enum" fields, you can emulate an "OR" query by making a separate boolean field for each enum-value, then adding a where("enum_<value>", "==", false) for every value that isn't part of the "OR" clause you want.
For example, consider your first desired query:
Give me all documents where the field status is open OR upcoming
You can accomplish this by splitting the status: string field into multiple boolean fields, one for each enum-value:
status_open: bool
status_upcoming: bool
status_suspended: bool
status_closed: bool
To perform your "where status is open or upcoming" query, you then do this:
where("status_suspended", "==", false).where("status_closed", "==", false)
How does this work? Well, because it's an enum, you know one of the values must have true assigned. So if you can determine that all of the other values don't match for a given entry, then by deduction it must match one of the values you originally were looking for.
See also
in/not-in/array-contains-in: https://firebase.google.com/docs/firestore/query-data/queries#in_and_array-contains-any
!=: https://firebase.googleblog.com/2020/09/cloud-firestore-not-equal-queries.html
I don't like everyone saying it's not possible.
it is if you create another "hacky" field in the model to build a composite...
for instance, create an array for each document that has all logical or elements
then query for .where("field", arrayContains: [...]
you can bind two Observables using the rxjs merge operator.
Here you have an example.
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/merge';
...
getCombinatedStatus(): Observable<any> {
return Observable.merge(this.db.collection('foo', ref => ref.where('status','==','open')).valueChanges(),
this.db.collection('foo', ref => ref.where('status','==','upcoming')).valueChanges());
}
Then you can subscribe to the new Observable updates using the above method:
getCombinatedStatus.subscribe(results => console.log(results);
I hope this can help you, greetings from Chile!!
We have the same problem just now, luckily the only possible values for ours are A,B,C,D (4) so we have to query for things like A||B, A||C, A||B||C, D, etc
As of like a few months ago firebase supports a new query array-contains so what we do is make an array and we pre-process the OR values to the array
if (a) {
array addObject:#"a"
}
if (b) {
array addObject:#"b"
}
if (a||b) {
array addObject:#"a||b"
}
etc
And we do this for all 4! values or however many combos there are.
THEN we can simply check the query [document arrayContains:#"a||c"] or whatever type of condition we need.
So if something only qualified for conditional A of our 4 conditionals (A,B,C,D) then its array would contain the following literal strings: #["A", "A||B", "A||C", "A||D", "A||B||C", "A||B||D", "A||C||D", "A||B||C||D"]
Then for any of those OR combinations we can just search array-contains on whatever we may want (e.g. "A||C")
Note: This is only a reasonable approach if you have a few number of possible values to compare OR with.
More info on Array-contains here, since it's newish to firebase docs
If you have a limited number of fields, definitely create new fields with true and false like in the example above. However, if you don't know what the fields are until runtime, you have to just combine queries.
Here is a tags OR example...
// the ids of students in class
const students = [studentID1, studentID2,...];
// get all docs where student.studentID1 = true
const results = this.afs.collection('classes',
ref => ref.where(`students.${students[0]}`, '==', true)
).valueChanges({ idField: 'id' }).pipe(
switchMap((r: any) => {
// get all docs where student.studentID2...studentIDX = true
const docs = students.slice(1).map(
(student: any) => this.afs.collection('classes',
ref => ref.where(`students.${student}`, '==', true)
).valueChanges({ idField: 'id' })
);
return combineLatest(docs).pipe(
// combine results by reducing array
map((a: any[]) => {
const g: [] = a.reduce(
(acc: any[], cur: any) => acc.concat(cur)
).concat(r);
// filter out duplicates by 'id' field
return g.filter(
(b: any, n: number, a: any[]) => a.findIndex(
(v: any) => v.id === b.id) === n
);
}),
);
})
);
Unfortunately there is no other way to combine more than 10 items (use array-contains-any if < 10 items).
There is also no other way to avoid duplicate reads, as you don't know the ID fields that will be matched by the search. Luckily, Firebase has good caching.
For those of you that like promises...
const p = await results.pipe(take(1)).toPromise();
For more info on this, see this article I wrote.
J
OR isn't supported
But if you need that you can do It in your code
Ex : if i want query products where (Size Equal Xl OR XXL : AND Gender is Male)
productsCollectionRef
//1* first get query where can firestore handle it
.whereEqualTo("gender", "Male")
.addSnapshotListener((queryDocumentSnapshots, e) -> {
if (queryDocumentSnapshots == null)
return;
List<Product> productList = new ArrayList<>();
for (DocumentSnapshot snapshot : queryDocumentSnapshots.getDocuments()) {
Product product = snapshot.toObject(Product.class);
//2* then check your query OR Condition because firestore just support AND Condition
if (product.getSize().equals("XL") || product.getSize().equals("XXL"))
productList.add(product);
}
liveData.setValue(productList);
});
For Flutter dart language use this:
db.collection("projects").where("status", whereIn: ["public", "unlisted", "secret"]);
actually I found #Dan McGrath answer working here is a rewriting of his answer:
private void query() {
FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection("STATUS")
.whereIn("status", Arrays.asList("open", "upcoming")) // you can add up to 10 different values like : Arrays.asList("open", "upcoming", "Pending", "In Progress", ...)
.addSnapshotListener(new EventListener<QuerySnapshot>() {
#Override
public void onEvent(#Nullable QuerySnapshot queryDocumentSnapshots, #Nullable FirebaseFirestoreException e) {
for (DocumentSnapshot documentSnapshot : queryDocumentSnapshots) {
// I assume you have a model class called MyStatus
MyStatus status= documentSnapshot.toObject(MyStatus.class);
if (status!= null) {
//do somthing...!
}
}
}
});
}
I have the following node js code that should list all items from a DynamoDB table,
import * as dynamoDbLib from "../../libs/dynamodb-lib";
import { success, failure } from "../../libs/response-lib";
export async function main(event, context) {
const params = {
TableName: "brands",
KeyConditionExpression: "brandId = :brandId",
ExpressionAttributeValues: {
":brandId": ''
}
};
try {
const result = await dynamoDbLib.call("query", params);
return success(result.Items);
} catch (e) {
console.log(e);
return failure({ status: false });
}
}
The id is in uuid format which when inserted from my node js was imported by using:
import uuid from "uuid";
then inserted to the table like:
brandId: uuid.v1()
Now when I query the items in the table I can only get only one record if and only if I hard coded the uuid of a record in the expression attribute value (either the KeyConditions or KeyConditionExpression parameter must be specified). So I thought about adding a regular expression to match all the uuids, my regular expression was copied from some solutions on the web but it didn't work, it was like the following:
[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}
and
\b[0-9a-f]{8}\b-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-\b[0-9a-f]{12}\b
and I have tried other examples but non of them worked, is it right to add a regular expression to get all the items, and if so what is the right regex for it?
Use a Scan operation to get all items in a table.
From the AWS Developer Guide:
The scan method reads every item in the table and returns all the data in the table. You can provide an optional filter_expression, so that only the items matching your criteria are returned. However, the filter is applied only after the entire table has been scanned.
I try to get first 10 items which satisfy condition from DynamoDB using lambda AWS. I was trying to use Limit parameter but it is (basis on that website)
https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#scan-property
"maximum number of items to evaluate (not necessarily the number of matching items)".
How to get 10 first items which satisfy my condition?
var AWS = require('aws-sdk');
var db = new AWS.DynamoDB();
exports.handler = function(event, context) {
var params = {
TableName: "Events", //"StreamsLambdaTable",
ProjectionExpression: "ID, description, endDate, imagePath, locationLat, locationLon, #nm, startDate, #tp, userLimit", //specifies the attributes you want in the scan result.
FilterExpression: "locationLon between :lower_lon and :higher_lon and locationLat between :lower_lat and :higher_lat",
ExpressionAttributeNames: {
"#nm": "name",
"#tp": "type",
},
ExpressionAttributeValues: {
":lower_lon": {"N": event.low_lon},
":higher_lon": {"N": event.high_lon}, //event.high_lon}
":lower_lat": {"N": event.low_lat},
":higher_lat": {"N": event.high_lat}
}
};
db.scan(params, function(err, data) {
if (err) {
console.log(err); // an error occurred
}
else {
data.Items.forEach(function(record) {
console.log(
record.name.S + "");
});
context.succeed(data.Items);
}
});
};
I think you already know the reason behind this: the distinction that DynamoDB makes between ScannedCount and Count. As per this,
ScannedCount — the number of items that were queried or scanned,
before any filter expression was applied to the results.
Count — the
number of items that were returned in the response.
The fix for that is documented right above this:
For either a Query or Scan operation, DynamoDB might return a LastEvaluatedKey value if the operation did not return all matching items in the table. To get the full count of items that match, take the LastEvaluatedKey value from the previous request and use it as the ExclusiveStartKey value in the next request. Repeat this until DynamoDB no longer returns a LastEvaluatedKey value.
So, the answer to your question is: use the LastEvaluatedKey from DynamoDB response and Scan again.