i want to delete record where company_id is "****" and gamer_id is "****".
How to write query for this .
public List<CompanyGamer> unfollowcompany(CompanyGamerForm CompanyGamerForm) throws NotFoundException {
String company_id = CompanyGamerForm.getCompany_id();
String gamer_id = CompanyGamerForm.getGamer_id();
Iterable<Key<CompanyGamer>> allKeys = ofy().load().type(CompanyGamer.class).filter("company_id=", company_id).filter("gamer_id=", gamer_id).keys();
ofy().delete().keys(allKeys); }
Please let me know what should be define in return ?
Have a look at the Objectify documentation for Queries https://github.com/objectify/objectify/wiki/Queries at the bottom of section "Executing Queries". "You can query for just keys, which will return Key objects much more efficiently than fetching whole objects"
Iterable<Key<Gamercompany>> allKeys = ofy().load().type(Gamercompany.class).filter("company_id=", compnyid).filter("gamer_id=",gamer_id).keys();
And then you can delete all entities corresponding to the keys:
ofy().delete().keys(allKeys);
Or if you do want to execute the query that returns the entities and not the keys, you could iterate over the Query and do:
ofy().delete().entity(thing); // asynchronous
or
ofy().delete().entity(thing).now(); // synchronous
However it would be less efficient than the first way.
Related
I have a code in to get all data in one collection in cosmo db, if the collection is empty then start to inserting.
The first time the code is run collection is empty however, SetIterator.HasMoreResults return True, even though the collection is empty.
Then there will be error raising Microsoft.Azure.Cosmos.CosmosException : Response status code does not indicate success: NotFound, and I have checked with a collection that is not empty the code run fine.
I can use try catch to handle it, but it does not seems to be a nice solution, Does anyone know how to check if the collection is empty?
var itemList = new List<T>();
using (FeedIterator<T> setIterator = _container.GetItemLinqQueryable<T>()
.ToFeedIterator())
{
while (setIterator.HasMoreResults)
{
foreach (var item in await setIterator.ReadNextAsync())
{
itemList.Add(item);
}
}
}
return itemList;
You can use indexing to get empty collection in cosmos db. To do this you can use unique indexes. Unique indexes are created to only those which doesn’t contain any documents.
Important
Unique indexes can be created only when the collection is empty
(contains no documents).
To create unique indexes on collections you can go through unique indexes
I am fairly new in this realm and any help is appreciated
I have a table in Dynamodb database named Tenant as below:
"TenantId" is the hash primary key and I have no other keys. And I have a field named "IsDeleted" which is boolean
Table Structure
I am trying to run a query to get the record with specified "TenantId" while it is not deleted ("IsDeleted == 0")
I can get a correct result by running the following code: (returns 0 item)
var filter = new QueryFilter("TenantId", QueryOperator.Equal, "2235ed82-41ec-42b2-bd1c-d94fba2cf9cc");
filter.AddCondition("IsDeleted", QueryOperator.Equal, 0);
var dbTenant = await
_genericRepository.FromQueryAsync(new QueryOperationConfig
{
Filter = filter
}).GetRemainingAsync();
But no luck when I try to get it with following code snippet (It returns the item which is also deleted) (returns 1 item)
var queryFilter = new List<ScanCondition>();
var scanCondition = new ScanCondition("IsDeleted", ScanOperator.Equal, new object[]{0});
queryFilter.Add(scanCondition);
var dbTenant2 = await
_genericRepository.LoadAsync("2235ed82-41ec-42b2-bd1c-d94fba2cf9cc", new DynamoDBOperationConfig
{
QueryFilter = queryFilter,
ConditionalOperator = ConditionalOperatorValues.And
});
Any Idea why ScanCondition has no effect?
Later I also tried this: (throw exception)
var dbTenant2 = await
_genericRepository.QueryAsync("2235ed82-41ec-42b2-bd1c-d94fba2cf9cc", new DynamoDBOperationConfig()
{
QueryFilter = new List<ScanCondition>()
{
new ScanCondition("IsDeleted", ScanOperator.Equal, 0)
}
}).GetRemainingAsync();
It throws with: "Message": "Must have one range key or a GSI index defined for the table Tenants"
Why does it complain about Range key or Index? I'm calling
public AsyncSearch<T> QueryAsync<T>(object hashKeyValue, DynamoDBOperationConfig operationConfig = null);
You simply cant query a table only giving a single primary key (only hash key). Because there is one and only one item for that primary key. The result of the Query would be that still that single item, which is actually Load operation not Query. You can only query if you have composite primary key in this case (Hash (TenantID) and Range Key) or GSI (which doesn't impose key uniqueness therefore accepts duplicate keys on index).
The second code attempts to filter the Load. DynamoDBOperationConfig's QueryFilter has a description ...
// Summary:
// Query filter for the Query operation operation. Evaluates the query results and
// returns only the matching values. If you specify more than one condition, then
// by default all of the conditions must evaluate to true. To match only some conditions,
// set ConditionalOperator to Or. Note: Conditions must be against non-key properties.
So works only with Query operations
Edit: So after reading your comments on this...
I dont think there conditional expressions are for read operations. AWS documents indicates they are for put or update operations. However, not being entirely sure on this since I never needed to do a conditional Load. There is no such thing like CheckIfExists functionality as well in general. You have to read the item and see if it exists. Conditional load will still consume read throughput so your only advantage would be only NOT retrieving it in other words saving the bandwith (which is very negligible for single item).
My suggestion is read it and filter it in your application layer. Dont query for it. However what you can also do is if you very need it you can use TenantId as hashkey and isDeleted for range key. If you do so, you always have to query when you wanna get a tenant. With the query you can set rangeKey(isDeleted) to 0 or 1. This isnt how I would do it. As I said, would just read it and filter it at my application.
Another suggestion thing could be setting a GSI on isDeleted field and writing null when it is 0. This way you can only see that attribute in your table when its only 1. GSI on such attribute is called sparse index. Later if you need to get all the tenants that are deleted (isDeleted=1) you can simply scan that entire index without conditions. When you are writing null when its 0 dynamoDB wont put it in the index at the first place.
I want select from Firestore collection just articles written NOT by me.
Is it really so hard?
Every article has field "owner_uid".
Thats it: I JUST want to write equivalent to "select * from articles where uid<>request.auth.uid"
TL;DR: solution found already: usages for languages/platforms: https://firebase.google.com/docs/firestore/query-data/queries#kotlin+ktx_5
EDIT Sep 18 2020
The Firebase release notes suggest there are now not-in and != queries. (Proper documentation is now available.)
not-in finds documents where a specified field’s value is not in a specified array.
!= finds documents where a specified field's value does not equal the specified value.
Neither query operator will match documents where the specified field is not present. Be sure the see the documentation for the syntax for your language.
ORIGINAL ANSWER
Firestore doesn't provide inequality checks. According to the documentation:
The where() method takes three parameters: a field to filter on, a comparison operation, and a value. The comparison can be <, <=, ==, >, or >=.
Inequality operations don't scale like other operations that use an index. Firestore indexes are good for range queries. With this type of index, for an inequality query, the backend would still have to scan every document in the collection in order to come up with results, and that's extremely bad for performance when the number of documents grows large.
If you need to filter your results to remove particular items, you can still do that locally.
You also have the option of using multiple queries to exclude a distinct value. Something like this, if you want everything except 12. Query for value < 12, then query for value > 12, then merge the results in the client.
For android it should be easy implement with Task Api.
Newbie example:
FirebaseFirestore db = FirebaseFirestore.getInstance();
Query lessQuery = db.collection("users").whereLessThan("uid", currentUid);
Query greaterQuery = db.collection("users").whereGreaterThan("uid", currentUid);
Task lessQuery Task = firstQuery.get();
Task greaterQuery = secondQuery.get();
Task combinedTask = Tasks.whenAllSuccess(lessQuery , greaterQuery)
.addOnSuccessListener(new OnSuccessListener<List<Object>>() {
#Override
public void onSuccess(List<Object> list) {
//This is the list of "users" collection without user with currentUid
}
});
Also, with this you can combine any set of queries.
For web there is rxfire
This is an example of how I solved the problem in JavaScript:
let articlesToDisplay = await db
.collection('articles')
.get()
.then((snapshot) => {
let notMyArticles = snapshot.docs.filter( (article) =>
article.data().owner_uid !== request.auth.uid
)
return notMyArticles
})
It fetches all documents and uses Array.prototype.filter() to filter out the ones you don't want. This can be run server-side or client-side.
Updating the answer of Darren G, which caused "TypeError: Converting circular structure to JSON". When we perform the filter operation, the whole firebase object was added back to the array instead of just the data. We can solve this by chaining the filter method with the map method.
let articles = []
let articlesRefs = await db.collection('articles').get();
articles = articlesRefs.docs
.filter((article) => article.data.uid !== request.auth.uid) //Get Filtered Docs
.map((article) => article.data()); //Process Docs to Data
return articles
FYI: This is an expensive operation because you will fetching all the articles from database and then filtering them locallly.
Track all user id in a single document (or two)
filter unwanted id out
Use "where in"
var mylistofidwherenotme = // code to fetch the single document where you tracked all user id, then filter yourself out
database.collection("articles").where("blogId", "in", mylistofidwherenotme)
let query = docRef.where('role','>',user_role).where('role','<',user_role).get()
This is not functioning as the "not equal" operation in firestore with string values
You can filter the array of objects within the javascript code.
var data=[Object,Object,Object] // this is your object array
var newArray = data.filter(function(el) {
return el.gender != 'Male';
});
Imagine the following function which is querying a GlobalSecondaryIndex and associated Range Key in order to find a limited number of results:
#Override
public List<Statement> getAllStatementsOlderThan(String userId, String startingDate, int limit) {
if(StringUtils.isNullOrEmpty(startingDate)) {
startingDate = UTC.now().toString();
}
LOG.info("Attempting to find all Statements older than ({})", startingDate);
Map<String, AttributeValue> eav = Maps.newHashMap();
eav.put(":userId", new AttributeValue().withS(userId));
eav.put(":receivedDate", new AttributeValue().withS(startingDate));
DynamoDBQueryExpression<Statement> queryExpression = new DynamoDBQueryExpression<Statement>()
.withKeyConditionExpression("userId = :userId and receivedDate < :receivedDate").withExpressionAttributeValues(eav)
.withIndexName("userId-index")
.withConsistentRead(false);
if(limit > 0) {
queryExpression.setLimit(limit);
}
List<Statement> statementResults = mapper.query(Statement.class, queryExpression);
LOG.info("Successfully retrieved ({}) values", statementResults.size());
return statementResults;
}
List<Statement> results = statementRepository.getAllStatementsOlderThan(userId, UTC.now().toString(), 5);
assertThat(results.size()).isEqualTo(5); // NEVER passes
The limit isn't respected whenever I query against the database. I always get back all results that match my search criteria so if I set the startingDate to now then I get every item in the database since they're all older than now.
You should use queryPage function instead of query.
From DynamoDBQueryExpression.setLimit documentation:
Sets the maximum number of items to retrieve in each service request
to DynamoDB.
Note that when calling DynamoDBMapper.query, multiple
requests are made to DynamoDB if needed to retrieve the entire result
set. Setting this will limit the number of items retrieved by each
request, NOT the total number of results that will be retrieved. Use
DynamoDBMapper.queryPage to retrieve a single page of items from
DynamoDB.
As they've rightly answered the setLimit or withLimit functions limit the number of records fetched only in each particular request and internally multiple requests take place to fetch the results.
If you want to limit the number of records fetched in all the requests then you might want to use "Scan".
Example for the same can be found here
In RavenDB I can store objects of type Products and Categories and they will automatically be located in different collections. This is fine.
But what if I have 2 logically completely different types of products but they use the same class? Or instead of 2 I could have a generic number of different types of products. Would it then be possible to tell Raven to split the product documents up in collections, lets say based on a string property available on the Product class?
Thankyou in advance.
EDIT:
I Have created and registered the following StoreListener that changes the collection for the documents to be stored on runtime. This results in the documents correctly being stored in different collections and thus making a nice, logically grouping of the documents.
public class DynamicCollectionDefinerStoreListener : IDocumentStoreListener
{
public bool BeforeStore(string key, object entityInstance, RavenJObject metadata)
{
var entity = entityInstance as EntityData;
if(entity == null)
throw new Exception("Cannot handle object of type " + EntityInstance.GetType());
metadata["Raven-Entity-Name"] = RavenJToken.FromObject(entity.TypeId);
return true;
}
public void AfterStore(string key, object entityInstance, RavenJObject metadata)
{
}
}
However, it seems I have to adjust my queries too in order to be able to get the objects back. My typical query of mine used to look like this:
session => session.Query<EntityData>().Where(e => e.TypeId == typeId)
With the 'typeId' being the name of the new raven collections (and the name of the entity type saved as a seperate field on the EntityData-object too).
How would I go about quering back my objects? I can't find the spot where I can define my collection at runtime prioring to executing my query.
Do I have to execute some raw lucene queries? Or can I maybe implement a query listener?
EDIT:
I found a way of storing, querying and deleting objects using dynamically defined collections, but I'm not sure this is the right way to do it:
Document store listener:
(I use the class defined above)
Method resolving index names:
private string GetIndexName(string typeId)
{
return "dynamic/" + typeId;
}
Store/Query/Delete:
// Storing
session.Store(entity);
// Query
var someResults = session.Query<EntityData>(GetIndexName(entity.TypeId)).Where(e => e.EntityId == entity.EntityId)
var someMoreResults = session.Advanced.LuceneQuery<EntityData>(GetIndexName(entityTypeId)).Where("TypeId:Colors AND Range.Basic.ColorCode:Yellow)
// Deleting
var loadedEntity = session.Query<EntityData>(GetIndexName(entity.TypeId)).Where(e =>
e.EntityId == entity.EntityId).SingleOrDefault();
if (loadedEntity != null)
{
session.Delete<EntityData>(loadedEntity);
}
I have the feeling its getting a little dirty, but is this the way to store/query/delete when specifying the collection names runtime? Or do I trap myself this way?
Stephan,
You can provide the logic for deciding on the collection name using:
store.Conventions.FindTypeTagName
This is handled statically, using the generic type.
If you want to make that decision at runtime, you can provide it using a DocumentStoreListner