According to this article:
https://blogs.msdn.microsoft.com/alexj/2009/10/12/tip-37-how-to-do-a-conditional-include/#comment-5225
I learned how to do a conditional include.
But now I need some lower level children like if a review has Marks, I need to fetch for each review the collection of Marks also. Any idea how to do this?
Query:
var movie = readOnlyRepository.GetById<Movie>(
movieId, false);
var dbquery = from mv in movie
select new
{
mv,
reviews = from review in mv.Reviews
where review.Mark = 10
select review
};
var result = dbquery.AsEnumerable().Select(x=> x.mv).First();
Given that Review has a collection of Marks I need that included in the result.
Related
Is it possible to get ElasticSearch document fields inside of loaded AR records?
Here is a gist that illustrates what I mean: https://gist.github.com/allomov/39c30905e94c646fb11637b45f43445d
In this case I want to avoid additional computation of total_price after getting response from ES. The solution that I currently see is to include the relationship and run total_price computation for each record, which is not so optimal way to perform this operation, as I see it.
result = Product.search("test", includes: :product_components).response
products_with_total_prices = result.map do |product|
{
product: product
total_price: product.product_components.map(&:price).compact.sum
}
end
Could you please tell if it is possible to mix ES document fields into AR loaded record?
As far as I'm aware it isn't possible to get a response that merges the document fields into the loaded record.
Usually I prefer to completely rely on the data in the indexed document where possible (using load: false as a search option), and only load the AR record(s) as a second step if necessary. For example:
result = Product.search("test", load: false).response
# If you also need AR records, could do something like:
product_ids = result.map(&:id)
products_by_id = {}
Product.where(id: product_ids).find_each do |ar_product|
products_by_id[ar_product.id] = ar_product
end
merged_result = result.map do |es_product|
es_product[:ar_product] = products_by_id[es_product.id]}
end
Additionally, it may be helpful to retrieve the document stored in the ES index for a specific record, which I would normally do by defining the following method in your Product class:
def es_document
return nil unless doc = Product.search_index.retrieve(self).presence
Hashie::Mash.new doc
end
You can use select: true and the with_hit method to get the record and the search document together. For your example:
result = Product.search("test", select: true)
products_with_total_prices =
result.with_hit.map do |product, hit|
{
product: product,
total_price: hit["_source"]["total_price"]
}
end
UPDATE:
I understood that the solution to my problem is doing subqueries, which apply a different filter each time, and they have a reduced result set. But I can't find a way to do that in MyBatis logic. Here is my query code
List<IstanzaMetadato> res = null;
SqlSession sqlSession = ConnectionFactory.getSqlSessionFactory().openSession(true);
try {
IstanzaMetadatoMapper mapper = sqlSession.getMapper(IstanzaMetadatoMapper.class);
IstanzaMetadatoExample example = new IstanzaMetadatoExample();
Iterator<Map.Entry<Integer, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<Integer, String> entry = it.next();
example.createCriteria().andIdMetadatoEqualTo(entry.getKey()).andValoreEqualTo(entry.getValue());
}
example.setDistinct(true);
res = mapper.selectByExample(example);
I need to execute a new selectByExample but inside the while cycle, and it has to query the previus "SELECTED" results....
Is there a Solution ?
ORIGINAL QUESTION:
I have this table structure
I have to select rows from the table with different filters, specified by the final user.
Those filters are specified by a couple (id_metadato, valore), in example you can have id_metadato = 3 and valore = "pippo";
the user can specify 0-n filters from the web page typing 0-n values inside the search boxes which are based on id_metadato
Obviusly, the more filters the users specifies, the more restriction would have the final query.
In example if the user fills only the first search box, the query will have only a filter and would provide all the rows that will have the couple (id_metadato, valore) specified by the user.
If he uses two search boxes, than the query will have 2 filters, and it will provide all the rows that verify the first condition AND the second one, after the "first subquery" is done.
I need to do this dinamically, and in the best efficient way. I can't simply add AND clause to my query, they have to filter and reduce the result set every time.
I can't do 0-n subqueries (Select * from ... IN (select * from ....) ) efficiently.
Is there a more elegant way to do that ? I'm reading dynamic SQL queries tutorials with MyBatis, but I'm not sure that is the correct way. I'm still trying to figure out the logic of the resosultio, then I will try to implement with MyBatis.
Thanks for the answers
MyBatis simplified a lot this process of nesting subqueries, it was sufficient to concatenate the filter criterias and to add
the excerpt of the code is the following
try {
IstanzaMetadatoMapper mapper = sqlSession.getMapper(IstanzaMetadatoMapper.class);
IstanzaMetadatoExample example = new IstanzaMetadatoExample();
Iterator<Map.Entry<Integer, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<Integer, String> entry = it.next();
if (listaIdUd.isEmpty()) {
example.createCriteria().andIdMetadatoEqualTo(entry.getKey()).andValoreEqualTo(entry.getValue());
example.setDistinct(true);
listaIdUd = mapper.selectDynamicNested(example);
continue;
}
example.clear();
example.createCriteria().andIdMetadatoEqualTo(entry.getKey()).andValoreEqualTo(entry.getValue()).andIdUdIn(listaIdUd);
example.setDistinct(true);
listaIdUd = mapper.selectDynamicNested(example);
}
The following code that I will show works correctly but I am wondering if there is a more efficient way of getting this done that can improve performance. The jest of this is that I got 2 tables profiles and followers. This code is supposed to modify 2 records in the profiles table and add a record in the followers table.
[HttpPost]
public void AddFollower(int id,following followers)
{
// me wants to follows followee
int me = Convert.ToInt32(User.Identity.Name);
using (var scope = new TransactionScope())
{
followers.me = me;
followers.ProfileID = id;
// Add new record on followers table
db.followings.Add(followers);
db.SaveChanges();
// Add +1 following for this persons profile & save it
var UserA = (from s in db.profiles where s.ID == me select s).FirstOrDefault();
UserA.following = UserA.following + 1;
db.Entry(UserA).State = System.Data.Entity.EntityState.Modified;
db.SaveChanges();
// Add +1 followers for this persons profile & save it
var UserB = (from s in db.profiles where s.ID == id select s).FirstOrDefault();
UserB.followers = profiles.followers + 1;
db.Entry(UserB).State = System.Data.Entity.EntityState.Modified;
db.SaveChanges();
scope.Complete();
}
}
The code above has a twitter like Functionality were if User A decides to follow User B then you most modify both their profiles in the database. This is done by increasing User A following count by 1 and increasing User B followers count by 1 and then offcourse creating that relationship in the followers table. This code works perfectly but I do not know if it could be written more efficient, I am essentially concerned that maybe this code might slow things down if there are a lot of users on the website.
It's really redundant to store the numbers. That is a computed value, which can easily calculated with a simple count.
I have been trying to figure out how to optimize the following query for the past few days and just not having much luck. Right now my test db is returning about 300 records with very little nested data, but it's taking 4-5 seconds to run and the SQL being generated by LINQ is awfully long (too long to include here). Any suggestions would be very much appreciated.
To sum up this query, I'm trying to return a somewhat flattened "snapshot" of a client list with current status. A Party contains one or more Clients who have Roles (ASPNET Role Provider), Journal is returning the last 1 journal entry of all the clients in a Party, same goes for Task, and LastLoginDate, hence the OrderBy and FirstOrDefault functions.
Guid userID = 'some user ID'
var parties = Parties.Where(p => p.BrokerID == userID).Select(p => new
{
ID = p.ID,
Title = p.Title,
Goal = p.Goal,
Groups = p.Groups,
IsBuyer = p.Clients.Any(c => c.RolesInUser.Any(r => r.Role.LoweredName == "buyer")),
IsSeller = p.Clients.Any(c => c.RolesInUser.Any(r => r.Role.LoweredName == "seller")),
Journal = p.Clients.SelectMany(c => c.Journals).OrderByDescending(j => j.OccuredOn).Select(j=> new
{
ID = j.ID,
Title = j.Title,
OccurredOn = j.OccuredOn,
SubCatTitle = j.JournalSubcategory.Title
}).FirstOrDefault(),
LastLoginDate = p.Clients.OrderByDescending(c=>c.LastLoginDate).Select(c=>c.LastLoginDate).FirstOrDefault(),
MarketingPlanCount = p.Clients.SelectMany(c => c.MarketingPlans).Count(),
Task = p.Tasks.Where(t=>t.DueDate != null && t.DueDate > DateTime.Now).OrderBy(t=>t.DueDate).Select(t=> new
{
ID = t.TaskID,
DueDate = t.DueDate,
Title = t.Title
}).FirstOrDefault(),
Clients = p.Clients.Select(c => new
{
ID = c.ID,
FirstName = c.FirstName,
MiddleName = c.MiddleName,
LastName = c.LastName,
Email = c.Email,
LastLogin = c.LastLoginDate
})
}).OrderBy(p => p.Title).ToList()
I think posting the SQL could give us some clues, as small things like the order of OrderBy coming before or after the projection could make a big difference.
But regardless, try extracting the Clients in a seperate query, this will simplify your query probably. And then include other tables like Journal and Tasks before projecting and see how this affects your query:
//am not sure what the exact query would be, and project it using ToList()
var clients = GetClientsForParty();
var parties = Parties.Include("Journal").Include("Tasks")
.Where(p=>p.BrokerID == userID).Select( p => {
....
//then use the in-memory clients
IsBuyer = clients.Any(c => c.RolesInUser.Any(r => r.Role.LoweredName == "buyer")),
...
}
)
In all cases, install EF profiler and have a look at how your query is affected. EF can be quiet surprising. Something like putting OrderBy before the projection, the same for all these FirstOrDefault or SingleOrDefault, they can all have a big effect.
And go back to the basics, if you are searching on LoweredRoleName, then make sure it is indexed so that the query is fast (even though that could be useless since EF could end up not making use of the covering index since it is querying so many other columns).
Also, since this is query is to view data (you will not alter data), don't forget to turn off Entity tracking, that will give you some performance boost as well.
And last, don't forget that you could always write your SQL query directly and project to your a ViewModel rather than anonymous type (which I see as a good practice anyhow) so create a class called PartyViewModel that includes the flatten view you are after, and use it with your hand-crafted SQL
//use your optimized SQL query that you write or even call a stored procedure
db.Database.SQLQuery("select * from .... join .... on");
I am writing a blog post about these issues around EF. The post is still not finished, but all in all, just be patient, use some of these tricks and observe their effect (and measure it) and you will reach what you want.
I have a table AccountSecurity which is a many-to-many table that relates Account entities and Securities. When I write the query below it returns all Securities that satisfy the where clause. However each Security instance in the list no longer has the reference to the AccountSecurity it came from. So when I do list[0].AccountSecurity it is empty. Is there anyway to include that information? I know I can rewrite the query to return AccountSecurities instead and use .Include("Security") on that, but I wonder if it can be done another way.
var list = (from acctSec in base.context.AccountSecurities
where acctSec.AccountId == accountId
select acctSec.Security).ToList();
UPDATE
Of course if I do two queries the graph gets populated properly, there has to be a way to do this in one shot.
var securities = (from acctSec in base.context.AccountSecurities
where acctSec.AccountId == accountId
select acctSec.Security).ToList();
//this query populates the AccountSecurities references within Security instances returned by query above
var xref = (from acctSec in base.context.AccountSecurities
where acctSec.AccountId == accountId
select acctSec).ToList();
var list = (from sec in base.context.Securities
.Include("AccountSecurity")
where sec.AccountSecurities.Any(as => as.AccountId == accountId)
select sec).ToList();
Try this:
var list = (from acctSec in base.context.AccountSecurities.Include("Security")
where acctSec.AccountId == accountId
select acctSec).ToList();
Then simply use the Security property as needed, and since it's read at the same time AccountSecurities is (single SQL with join), it will be very efficient.