I have the next entity to persist with DB4O which is being persisted in db perfectly.
public class Message {
private String userFrom;
private String userTo;
private String message;
private Date received;
private Boolean readed;
...
}
I've the problem trying to recover the persisted objects throught one query.
With SQL it would seen at thus.
SELECT * FROM Message WHERE readed = 0
AND ((userFrom = 'asd' AND userTo = 'qwe') OR (userFrom = 'qwe' AND userTo = 'asd'))
ORDER BY received DESC
My current wrong DB4O Query can be look like below.
Query query = super.getQuery();
query.constrain(Message.class);
Query readedQuery = query.descend("readed");
Query receivedQuery = query.descend("received");
Query userToQuery = query.descend("userTo");
Query userFromQuery = query.descend("userFrom");
receivedQuery.orderDescending()
.constrain(readedQuery.constrain(Boolean.FALSE))
.and(userToQuery.constrain("asd")
.and(userFromQuery.constrain("qwe"))
.or(userToQuery.constrain("qwe")
.and(userFromQuery.constrain("asd"))));
return query.execute();
Solution:
receivedQuery.sortBy(new Comparator<Message>() {
#Override
public int compare(Message message1, Message message2) {
return message1.getReceived().after(message2.getReceived()) ? 1 : -1;
}
}).readedQuery.constrain(Boolean.FALSE)
.and(userToQuery.constrain("asd")
.and(userFromQuery.constrain("qwe"))
.or(userToQuery.constrain("qwe")
.and(userFromQuery.constrain("asd"))));
Related
I am trying to achieve the Groupby key based on custom object in cloud data flow pipe line.
public static void main(String[] args) {
Pipeline pipeline = Pipeline.create(PipelineOptionsFactory.create());
List<KV<Student,StudentValues>> studentList = new ArrayList<>();
studentList.add(KV.of(new Student("pawan", 10,"govt"),
new StudentValues("V1", 123,"govt")));
studentList.add(KV.of(new Student("pawan", 13223,"word"),
new StudentValues("V2", 456,"govt")));
PCollection<KV<Student,StudentValues>> pc =
pipeline.apply(Create.of(studentList));
PCollection<KV<Student, Iterable<StudentValues>>> groupedWords =
pc.apply(GroupByKey.<Student,StudentValues>create());
}
I just wanted to groupBy both the PCollection record based on the Student object.
#DefaultCoder(AvroCoder.class)
static class Student /*implements Serializable*/{
public Student(){}
public Student(String n, Integer i, String sc){
name = n;
id = i;
school = sc;
}
public String name;
public Integer id;
public String school;
#Override
public boolean equals(Object obj) {
System.out.println("obj = "+obj);
System.out.println("this = "+this);
Student stObj= (Student)obj;
if (stObj.Name== this.Name){
return true;
} else{
return false;
}
}
}
I have overridden the equals method of my custom class, but each time i am getting same instance of Student object to compare inside equals method.
Ideally it sholud compare first student key with second one.
Whats wrong i am doing here.
Why do you think you are doing anything wrong? The keys of each element are serialized (using the AvroCoder you specified) and the GroupByKey can group all of the elements with the same serialized representation together. After that it doesn't need to compare the students to make sure that the values with the same key have been grouped together.
I have the following linq query
internal List<ZipCodeInfo> GetInfoFromZipCode(string zipCode)
{
using (DbContext context = new DbContext())
{
IQueryable<ZipCodeInfo> results;
results = (from a in context.Address
where a.ZipCode.Equals(zipCode)
select new ZipCodeInfo
{
Field1 = a.Field1,
Field2 = a.Field2,
Field3 = a.Field3
});
return results.ToList();
}
}
But the query itself takes around 5-6 seconds to be completed. I've executed the counterpart query on SQL and it takes almost nothing to complete. Why is it taking that long? The query at the end just returns 4 matches so there is not that much to do here..
This query is part of a Controller class and I am using ASP.NET Core and EntityFramework Core.
The SQL query looks like this, btw.
SELECT *
FROM Address
WHERE ZipCode = '29130'
You can rewrite above query as shown below.Please let us know about the performance now.
internal List<ZipCodeInfo> GetInfoFromZipCode(string zipCode)
{
using (DbContext context = new DbContext())
{
//disabled tracking
context.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking;
IQueryable<ZipCodeInfo> results;
results = (from a in context.Address
where a.ZipCode.Equals(zipCode)
select new ZipCodeInfo
{
Field1 = a.Field1,
Field2 = a.Field2,
Field3 = a.Field3
});
return results.ToList();
}
}
I don't know what version of .Net and entity frameworks are you using, but I found an interesting article here on MSDN. You can go through it. But code can be used as below:
static readonly Func<DbEntities, IQueryable<ZipCodeInfo>> s_compiledQuery2 =
CompiledQuery.Compile<DbEntities, IQueryable<ZipCodeInfo>>(
(ctx, total) => from a in context.Address
where a != null and a != ""
a.ZipCode.ToUpper().Equals(zipCode.ToUpper())
select new ZipCodeInfo
{
Field1 = a.Field1,
Field2 = a.Field2,
Field3 = a.Field3
});
internal List<ZipCodeInfo> GetInfoFromZipCode(string zipCode)
{
using (DbEntities context = new DbEntities())
{
IQueryable<ZipCodeInfo> zipCodes = s_compiledQuery2.Invoke(context, zipCode);
return zipCodes.ToList();
}
}
At this point I don't have any remote database to test but again delay to fetch the result of these kind of query will also depends on N\W and number of records being fetched. You can try this solution.
I have an MVC 3 appliation which I have many integer fields on a form. They all require range validation but the ranges exists in a table in my database. So I would like to create a reusable remote validation tool which will look up the min and max value and return the validation to the view.
I am updating this with some example code of what I would like to do to see my request might clarify what I am looking for:
In my validation class:
[Remote("CheckIntegerRange", "Validation", ErrorMessage = "Value outside of range")]
public object UW1_Web_Tension_SP { get; set; }
[Remote("CheckIntegerRange", "Validation", ErrorMessage = "Value outside of range")]
public object UW2_Web_Tension_SP { get; set; }
[Remote("CheckIntegerRange", "Validation", ErrorMessage = "Value outside of range")]
public object UW3_Web_Tension_SP { get; set; }
In my ValidationController I tried to create a function with multiple parameters but I dont think I can - however I think it shows what I am trying to do more clearly:
public class ValidationController : Controller
{
public JsonResult CheckIntegerRange(int integer, string EntityName, string AttributeName)
{
var result = false;
int MinInteger = 0;
int MaxInteger = 100;
//declare recipe entities
var context = new MadicoRecipeEntities();
//set sql statements and get description, etc from attributes view
var esqlIntegerAttributeDetails = "SELECT VALUE c FROM MadicoRecipeEntities.v_AttributeIntegerRangeDetails AS c " +
"WHERE c.EntityName = '" + EntityName + "' AND c.Attribute = '" + AttributeName + "'";
var queryAttributeDetails = context.CreateQuery<v_AttributeIntegerRangeDetails>(esqlIntegerAttributeDetails);
var RecipeAttributes = queryAttributeDetails.ToList();
foreach (var AttributeDetails in RecipeAttributes)
{
MinInteger = AttributeDetails.Min;
MaxInteger = AttributeDetails.Max;
}
return Json(result, JsonRequestBehavior.AllowGet);
}
}
I have found the following post on the asp.net forums which handled my first obstacle - passing different named attributes to the same validator. However, in this example the name is passed in generically - I need to have the name in order to query the table to get the applicable min and max ranges.
http://forums.asp.net/t/1625928.aspx/3/10
Can anyone point me in the right direction?
Thanks!
It is called remote validation! Here is an example:
remote validation
Let's say I have this code:
class Score
{
public Update(int score)
{
update score but do not call (context.SaveChanges())
}
}
class Foo
{
public DoSomething(int update)
{
Score score = new Score();
score.Update(2);
SomeObj obj = (select object);
obj.Soo = 3;
context.SaveChanges();
}
}
Basically to make it work, I need to explicity provide SaveChanges in method Update. But when I have 4 such methods in row, and 34243 users want to update data, I don't think saving for each one in 4 trips would be a good idea.
Is there way in EF4.1 to delay database update the last moment, in provided example, Or I'm forced to explicity save for each method ?
EDIT:
For clarification. I tried to do not call SaveChanges in external method, and only one time where the changes mu be saved.
I will give an real example:
public class ScoreService : IScoreService
{
private JamiContext _ctx;
private IRepository<User> _usrRepo;
public ScoreService(IRepository<User> usrRepo)
{
_ctx = new JamiContext();
_usrRepo = usrRepo;
}
public void PostScore(int userId, GlobalSettings gs, string name)
{
User user = _ctx.UserSet.Where(x => x.Id == userId).FirstOrDefault();
if (name == "up")
{
user.Rating = user.Rating + gs.ScoreForLike;
}
else if (name == "down")
{
user.Rating = user.Rating - Math.Abs(gs.ScoreForDislike);
}
}
}
And Now:
public PostRating LikeDislike(User user, int postId, int userId, GlobalSettings set, string name)
{
PostRating model = new PostRating();
var post = (from p in _ctx.PostSet
where p.Id == postId
select p).FirstOrDefault();
if (name == "up")
{
post.Like = post.Like + 1;
model.Rating = post.Like - post.Dislike;
}
else if (name == "down")
{
post.Dislike = post.Dislike + 1;
model.Rating = post.Like - post.Dislike;
}
PostVote pv = new PostVote();
pv.PostId = post.Id;
pv.UserId = user.Id;
_ctx.PostVoteSet.Add(pv);
_scoreSrv.PostScore(userId, set, name);
_ctx.SaveChanges();
return model;
}
I this case user rating do not update, Until I call SaveChanges in PostScore
In your example it looks like PostScore and LikeDislike use different context instances. That is the source of your problem and there is no way to avoid calling multiple SaveChanges in that case. The whole operation is single unit of work and because of that it should use single context instance. Using multiple context instances in this case is wrong design.
Anyway even if you call single SaveChanges you will still have separate roundtrip to the database for each updated, inserted or deleted entity because EF doesn't support command batching.
The way to delay database update to the last moment is by not calling SaveChanges until the last moment.
You have complete control over this code, and if your code is calling SaveChanges after every update, then that needs changing.
This not really solves my entire problem, but at least I can use single instance of Context:
With Ninject:
Bind<JamiContext>().To<JamiContext>().InRequestScope();
And then constructor:
private JamiContext _ctx;
private IRepository<User> _usrRepo;
public ScoreService(IRepository<User> usrRepo, JamiContext ctx)
{
_ctx = ctx;
_usrRepo = usrRepo;
}
I have been scratching my head all morning behind this but still haven't been able to figure out what might be causing this.
I have a composite repository object that references two other repositories. I'm trying to instantiate a Model type in my LINQ query (see first code snippet).
public class SqlCommunityRepository : ICommunityRepository
{
private WebDataContext _ctx;
private IMarketRepository _marketRepository;
private IStateRepository _stateRepository;
public SqlCommunityRepository(WebDataContext ctx, IStateRepository stateRepository, IMarketRepository marketRepository)
{
_ctx = ctx;
_stateRepository = stateRepository;
_marketRepository = marketRepository;
}
public IQueryable<Model.Community> Communities
{
get
{
return (from comm in _ctx.Communities
select new Model.Community
{
CommunityId = comm.CommunityId,
CommunityName = comm.CommunityName,
City = comm.City,
PostalCode = comm.PostalCode,
Market = _marketRepository.GetMarket(comm.MarketId),
State = _stateRepository.GetState(comm.State)
}
);
}
}
}
The repository objects that I'm passing in look like this
public class SqlStateRepository : IStateRepository
{
private WebDataContext _ctx;
public SqlStateRepository(WebDataContext ctx)
{
_ctx = ctx;
}
public IQueryable<Model.State> States
{
get
{
return from state in _ctx.States
select new Model.State()
{
StateId = state.StateId,
StateName = state.StateName
};
}
}
public Model.State GetState(string stateName)
{
var s = (from state in States
where state.StateName.ToLower() == stateName
select state).FirstOrDefault();
return new Model.State()
{
StateId = s.StateId,
StateName = s.StateName
};
}
AND
public class SqlMarketRepository : IMarketRepository
{
private WebDataContext _ctx;
public SqlMarketRepository(WebDataContext ctx)
{
_ctx = ctx;
}
public IQueryable<Model.Market> Markets
{
get
{
return from market in _ctx.Markets
select new Model.Market()
{
MarketId = market.MarketId,
MarketName = market.MarketName,
StateId = market.StateId
};
}
}
public Model.Market GetMarket(int marketId)
{
return (from market in Markets
where market.MarketId == marketId
select market).FirstOrDefault();
}
}
This is how I'm wiring it all up:
WebDataContext ctx = new WebDataContext();
IMarketRepository mr = new SqlMarketRepository(ctx);
IStateRepository sr = new SqlStateRepository(ctx);
ICommunityRepository cr = new SqlCommunityRepository(ctx, sr, mr);
int commCount = cr.Communities.Count();
The last line in the above snippet is where it fails. When I debug through the instantiation (new Model.Community), it never goes into any of the other repository methods. I do not have a relationship between the underlying tables behind these three objects. Would this be the reason that LINQ to SQL is not able to build the expression tree right?
These are non-hydrated queries, not fully-hydrated collections.
The Communities query differs from the other two because it calls methods as objects are hydrated. These method calls are not translatable to SQL.
Normally this isn't a problem. For example: if you say Communities.ToList(), it will work and the methods will be called from the objects as they are hydrated.
If you modify the query such that the objects aren't hydrated, for example: when you say Communities.Count(), linq to sql attempts to send the method calls into the database and throws since it cannot. It does this even though those method calls ultimately would not affect the resulting count.
The simplest fix (if you truly expect fully hydrated collections) is to add ToList to the community query, hydrating it.
Try adding another repository method that looks like this:
public int CommunitiesCount()
{
get { return _ctx.Communities.Count(); }
}
This will allow you to return a count without exposing the entire object tree to the user, which is what I think you're trying to do anyway.
As you may have already guessed, I suspect that what you are calling the anonymous types are at fault (they're not really anonymous types; they are actual objects, which you are apparently partially populating in an effort to hide some of the fields from the end user).