I want to create query. I'm using FirestoreRecyclerAdapter. Initialising adapter I got error:
FAILED_PRECONDITION: The query requires an index.
How I can create index if eventId in my case is dynamic value?
I'm sure this is basic thing, cause I'm doing all according to manual. As I read in the documentation, sets of data should have crossing sets of keys ie {dataId, true} in both events and users in my case. Please help me where to go for solution.
Query query = mFirebaseFirestore.collection(EVENT_INFO).document(eventId)
.collection(USERS)
.whereEqualTo(FIELD_AGE, guestAge)
.whereEqualTo(EVENTS_ATTENDED + "."+ eventId, true)
.orderBy(FIELD_FAMILYNAME, Query.Direction.ASCENDING);
At that moment there is no such an options to do things beautifull with Firestore. So we should think of hiding items based on custom criteria inside onBindViewHolder method in our FirestoreRecyclerAdapter. Like follows:
protected void onBindViewHolder(GuestHolder holder, int position, GuestItem guest) {
Map<String, Boolean> map = guest.getEventsAttended();
if (map != null && map.containsKey(eventId)) {
holder.itemView.setVisibility(View.VISIBLE);
} else {
holder.itemView.setVisibility(View.GONE);
holder.itemView.setLayoutParams(new RecyclerView.LayoutParams(0, 0));
}}
Hope this helps someone.
Related
Hi I am newbie to dynamoDB. Below is the schema of the dynamo table
{
"user_id":1, // partition key
"dob":"1991-09-12", // sort key
"movies_watched":{
"1":{
"movie_name":"twilight",
"movie_released_year":"1990",
"movie_genre":"action"
},
"2":{
"movie_name":"harry potter",
"movie_released_year":"1996",
"movie_genre":"action"
},
"3":{
"movie_name":"lalaland",
"movie_released_year":"1998",
"movie_genre":"action"
},
"4":{
"movie_name":"serendipity",
"movie_released_year":"1999",
"movie_genre":"action"
}
}
..... 6 more attributes
}
I want to insert a new item if the item(that user id with dob) did not exist, otherwise add the movies to existing movies_watched map by checking if the movie is not already available the movies_watched map .
Currently, I am trying to use update(params) method.
Below is my approach:
function getInsertQuery (item) {
const exp = {
UpdateExpression: 'set',
ExpressionAttributeNames: {},
ExpressionAttributeValues: {}
}
Object.entries(item).forEach(([key, item]) => {
if (key !== 'user_id' && key !== 'dob' && key !== 'movies_watched') {
exp.UpdateExpression += ` #${key} = :${key},`
exp.ExpressionAttributeNames[`#${key}`] = key
exp.ExpressionAttributeValues[`:${key}`] = item
}
})
let i = 0
Object.entries(item. movies_watched).forEach(([key, item]) => {
exp.UpdateExpression += ` movies_watched.#uniqueID${i} = :uniqueID${i},`
exp.ExpressionAttributeNames[`#uniqueID${i}`] = key
exp.ExpressionAttributeValues[`:uniqueID${i}`] = item
i++
})
exp.UpdateExpression = exp.UpdateExpression.slice(0, -1)
return exp
}
The above method just creates update expression with expression names and values for all top level attributes as well as nested attributes (with document path).
It works well if the item is already available by updating movies_watched map. But throws exception if the item is not available and while inserting. Below is exception:
The document path provided in the update expression is invalid for update
However, I am still not sure how to check for duplicate movies in movies_watched map
Could someone guide me in right direction, any help is highly appreciated!
Thanks in advance
There is no way to do this, given your model, without reading an item from DDB before an update (at that point the process is trivial). If you don't want to impose this additional read capacity on your table for update, then you would need to re-design your data model:
You can change movies_watched to be a Set and hold references to movies. Caveat is that Set can contain only Numbers or Strings, thus you would have movie id or name or keep the data but as JSON Strings in your Set and then parse it back into JSON on read. With SET you can perform ADD operation on the movies_watched attribute. https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.UpdateExpressions.html#Expressions.UpdateExpressions.ADD
You can go with single table design approach and have these movies watched as separate items with (PK:userId and SK:movie_id). To get a user you would perform a query and specify only PK=userId -> you will get a collection where one item is your user record and others are movies_watched. If you are new to DynamoDB and are learning the ropes, then I would suggest go with this approach. https://www.alexdebrie.com/posts/dynamodb-single-table/
I have an Articles table and it has a relation with the Authors table. Each author has a name property. I want to make a GET request for the articles and receive the articles sorted based on their author's name.
When I use _sort=author in the url parameters, I get the articles sorted based on the author object's ID.
When I use _sort=author.name in the url parameters, I get the articles in a seemingly random order but definitely not based on author.name.
How can I get the data sorted based on author.name?
I use mongoDB as my database.
That is the default behavior of _sort. However, you can simply accomplish this by overriding the find method in api/article/services/article.js to sort by Author's name like so:
module.exports = {
async find(params, populate) {
let result = await strapi.query('article').find(params, populate);
if (params._sort == 'author')
return result.sort((a, b) => (a.author.name > b.author.name) ? 1 : -1);
return result;
},
}
Check the documentation for customizing services to get more info: https://strapi.io/documentation/v3.x/concepts/services.html#concept
I'm using firestore for my project to store data , my issue is that i can not
filter data just the way codelab filter does .The result of that query gives me the whole collections docs which means the filter is not working.
I've tried many workarounds and find out that only when I cascade whereEqualto()
methods in one line I get what I want of specific docs , but this approach (cascading whereEqualTo inline) is not flexible when giving the user a way to filter searches.I just want to know why that code is not working for me.
// Does not work
Query query = mFirestore.collection("restaurants");
// Category (equality filter)
if (filters.hasCategory()) {
query = query.whereEqualTo("category", filters.getCategory());
}
// City (equality filter)
if (filters.hasCity()) {
query = query.whereEqualTo("city", filters.getCity());
}
This works:
query.whereEqualTo("realEstateType", realEstateType).whereEqualTo("propertyStatus", propertyStatus).whereEqualTo("propertyPhysicalStatus", propertyPhysicalConditionS).addSnapshotListener(new EventListener<QuerySnapshot>() {
#Override
public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
}
}
});
I figured it out ,It seems that I was not assigning to query object the filter as follows:
query = query.whereEqualTo("fieldPath" , ...);
I'm trying to execute a query from java against a Map/Reduce view I have created on the CouchDB.
My map function looks like the following:
function(doc) {
if(doc.type == 'SPECIFIC_DOC_TYPE_NAME' && doc.userID){
for(var g in doc.groupList){
emit([doc.userID,doc.groupList[g].name],1);
}
}
}
and Reduce function:
function (key, values, rereduce) {
return sum(values);
}
The view seems to be working when executed from the Futon interface (without keys specified though).
What I'm trying to do is to count number of some doc types belonging to a single group. I want to query that view using 'userID' and name of the group as a keys.
I'm using Ektorp library for managing CouchDB data, if I execute this query without keys it returns the scalar value, otherwise it just prints an error saying that for reduce query group=true must be specified.
I have tried the following:
ViewQuery query = createQuery("some_doc_name");
List<String> keys = new ArrayList<String>();
keys.add(grupaName);
keys.add(uzytkownikID);
query.group(true);
query.groupLevel(2);
query.dbPath(db.path());
query.designDocId(stdDesignDocumentId);
query.keys(keys);
ViewResult r = db.queryView(query);
return r.getRows().get(0).getValueAsInt();
above example works without 'keys' specified.
I have other queries working with ComplexKey like eg:
ComplexKey key = ComplexKey.of(userID);
return queryView("list_by_userID",key);
but this returns only a list of type T (List) - using CouchDbRepositorySupport of course - and cannot be used with reduce type queries (from what I know).
Is there any way to execute the query with reduce function specified and a complex key with 2 or more values using Ektorp library? Any examples highly appreciated.
Ok, I've found the solution using trial and error approach:
public int getNumberOfDocsAssigned(String userID, String groupName) {
ViewQuery query = createQuery("list_by_userID")
.group(true)
.dbPath(db.path())
.designDocId(stdDesignDocumentId)
.key(new String[]{userID,groupName});
ViewResult r = db.queryView(query);
return r.getRows().get(0).getValueAsInt();
}
So, the point is to send the complex key (not keys) actually as a single (but complex) key containing the String array, for some reason method '.keys(...)' didn't work for me (it takes a Collection as an argument). (for explanation on difference between .key() and .keys() see Hendy's answer)
This method counts all documents assigned to the specific user (specified by 'userID') and specific group (specified by 'groupName').
Hope that helps anybody executing map/reduce queries for retrieving scalar values from CouchDB using Ektorp query.
Addition to Kris's answer:
Note that ViewQuery.keys() is used when you want to query for documents matching a set of keys, not for finding document(s) with a complex key.
Like Kris's answer, the following samples will get document(s) matching the specified key (not "keys")
viewQuery.key("hello"); // simple key
viewQuery.key(documentSlug); // simple key
viewQuery.key(new String[] { userID, groupName }); // complex key, using array
viewQuery.key(ComplexKey.of(userID, groupName)); // complex key, using ComplexKey
The following samples, on the other hand, will get document(s) matching the specified keys, where each key may be either a simple key or a complex key:
// simple key: in essence, same as using .key()
viewQuery.keys(ImmutableSet.of("hello"));
viewQuery.keys(ImmutableSet.of(documentSlug1));
// simple keys
viewQuery.keys(ImmutableSet.of("hello", "world"));
viewQuery.keys(ImmutableSet.of(documentSlug1, documentSlug2));
// complex key: in essence, same as using .key()
viewQuery.keys(ImmutableSet.of(
new String[] { "hello", "world" } ));
viewQuery.keys(ImmutableSet.of(
new String[] { userID1, groupName1 } ));
// complex keys
viewQuery.keys(ImmutableSet.of(
new String[] { "hello", "world" },
new String[] { "Mary", "Jane" } ));
viewQuery.keys(ImmutableSet.of(
new String[] { userID1, groupName1 },
new String[] { userID2, groupName2 } ));
// a simple key and a complex key. while technically possible,
// I don't think anybody actually does this
viewQuery.keys(ImmutableSet.of(
"hello",
new String[] { "Mary", "Jane" } ));
Note: ImmutableSet.of() is from guava library.
new Object[] { ... } seems to have same behavior as ComplexKey.of( ... )
Also, there are startKey() and endKey() for querying using partial key.
To send an empty object {}, use ComplexKey.emptyObject(). (only useful for partial key querying)
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