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Apache Ignite Group By Linq Query Issue

i'm trying to join three caches with two of them are left outer joined,also has group by clause. With the below query i ran into strange issue, the generated sql was not correct.
var query = (from service in serviceCache
join meetingService in meetingServiceCache.DefaultIfEmpty() on service.Value.ServiceId equals meetingService.Value.ServiceId
join meeting in meetingCache.DefaultIfEmpty() on meetingService.Value.MeetingId equals meeting.Value.MeetingId
group new { service, meeting } by service.Value.ServiceId into g
select new {
service.Value.ServiceId,
lastMeeting = g.Select(x=>x.meeting.Value.CreatedDate).Max()
}).ToCacheQueryable().GetFieldsQuery.Sql;
The generated query looks like below
select _T0.SERVICEID,min(_T0.CreatedDate) from MEETINGSCHEMA.SERVICES as _T0
left outer join (select _T1.*,_T1.KEY,_T1.VAL from MEETINGSCHEMA.MEETINGSERVICE as _T1) as _T2 on (_T2.SERVICEID= _T0.SERVICEID)
left outer join (select _T3.*,_T3.KEY,_T3.VAL from MEETINGSCHEMA.MEETINGS as _T3) as _T4 on (_T4.MEETINGID= _T3.MEETINGID)
group by (_T0.SERVICEID)
In selected columns the createdDate should be selected from _T4 reference,But it's always selected from first table alias thus the query was failing always reporting CreatedDate as invalid column.I Suspect something wrong with linq to sql translation.
Please let me know if i'm doing any mistake. Also the code snippet was typed by hand with out intellisense, pardon me incase of typos.

After grouping you can select only Key property or aggregation functions. Also LEFT JOIN should be written in different way.
var query =
from service in serviceCache
join meetingService in meetingServiceCache on service.Value.ServiceId equals meetingService.Value.ServiceId into j
from meetingService in j.DefaultIfEmpty()
join meeting in meetingCache on meetingService.Value.MeetingId equals meeting.Value.MeetingId into j
from meeting in j.DefaultIfEmpty()
group new { service, meeting } by service.Value.ServiceId into g
select new
{
ServiceId = g.Key,
lastMeeting = g.Max(x => x.meeting.Value.CreatedDate)
};

This seems to be a bug in Ignite, I've filed a ticket.
The workaround is to reorder the joined tables and put meeting first, something like this:
var query = (from meeting in meetingCache
join meetingService in meetingServiceCache.DefaultIfEmpty() on meeting.Value.MeetingId equals meetingService.Value.MeetingId
join service in serviceCache service.Value.ServiceId equals meetingService.Value.ServiceId
group new { service, meeting } by service.Value.ServiceId into g
select new {
service.Value.ServiceId,
lastMeeting = g.Select(x=>x.meeting.Value.CreatedDate).Max()
}).ToCacheQueryable().GetFieldsQuery.Sql;
Another workaround is to use raw SQL for this query.

Is it possible to use WHERE by some IF condition for PostgreSQL?

I have the following SQL request for a report.
select customers."AppId", second_dep "SecondDeps", first_dep "FirstDeps",
customers_count "Customers", registrations "Registrations"
From (select Count("AppId") as customers_count, "AppId"
FROM "Customers"
join "Advertisers" A on "Customers"."AdvertiserId" = A."AdvertiserId"
join "Categories" C2 on "Customers"."CategoryId" = C2."CategoryId"
where A."Name" in (:AdvertiserNames)
AND C2."Name" = :CategoryName
GROUP BY "AppId"
) as customers
left join
(select C."AppId", count(CE.*) as second_dep
from "CustomerEvents" as CE
inner join "Customers" C on CE."CustomerId" = C."CustomerId"
WHERE "EventType" = 'deposit'
and "Again" = TRUE
GROUP BY C."AppId") as dep2 on customers."AppId" = dep2."AppId"
left join
(select C."AppId", count(CE.*) as first_dep
from "CustomerEvents" as CE
inner join "Customers" C on CE."CustomerId" = C."CustomerId"
WHERE "EventType" = 'deposit'
and "Again" = false
GROUP BY C."AppId") as dep on customers."AppId" = dep."AppId"
left join
(select C."AppId", count(CE.*) as registrations
from "CustomerEvents" as CE
inner join "Customers" C on CE."CustomerId" = C."CustomerId"
WHERE "EventType" = 'registration'
GROUP BY C."AppId") as regs on regs."AppId" = customers."AppId";
The string with problem is
where A."Name" in (:AdvertiserNames)
I would like to skip it if AdvertiserNames is empty. Is it possible? Ok, I can check it on the code side, but this way will leads me to copy whole request with some small difference (I mean if AdvertiserNames is empty run SQL without where A."Name" in (:AdvertiserNames)). Or I can use concatenation to get suitable SQL. I dont like this way too.
About my technology stack. It's .NET Core 2.2 with PostgreSQL. Here is the code of whole report method:
public IQueryable<ByApplicationsReportModel> ByApplications(string category, List<string> advertisers)
{
var rawSql = new RawSqlString(#"
select customers.""AppId"", second_dep ""SecondDeps"", first_dep ""FirstDeps"",
customers_count ""Customers"", registrations ""Registrations""
From (select Count(""AppId"") as customers_count, ""AppId""
FROM ""Customers""
join ""Advertisers"" A on ""Customers"".""AdvertiserId"" = A.""AdvertiserId""
join ""Categories"" C2 on ""Customers"".""CategoryId"" = C2.""CategoryId""
where A.""Name"" in (#AdvertiserNames)
AND C2.""Name"" = #CategoryName
GROUP BY ""AppId""
) as customers
left join
(select C.""AppId"", count(CE.*) as second_dep
from ""CustomerEvents"" as CE
inner join ""Customers"" C on CE.""CustomerId"" = C.""CustomerId""
WHERE ""EventType"" = 'deposit'
and ""Again"" = TRUE
GROUP BY C.""AppId"") as dep2 on customers.""AppId"" = dep2.""AppId""
left join
(select C.""AppId"", count(CE.*) as first_dep
from ""CustomerEvents"" as CE
inner join ""Customers"" C on CE.""CustomerId"" = C.""CustomerId""
WHERE ""EventType"" = 'deposit'
and ""Again"" = false
GROUP BY C.""AppId"") as dep on customers.""AppId"" = dep.""AppId""
left join
(select C.""AppId"", count(CE.*) as registrations
from ""CustomerEvents"" as CE
inner join ""Customers"" C on CE.""CustomerId"" = C.""CustomerId""
WHERE ""EventType"" = 'registration'
GROUP BY C.""AppId"") as regs on regs.""AppId"" = customers.""AppId""");
var advertisersParam = new NpgsqlParameter("AdvertiserNames",
string.Join(",", advertisers) );
var categoryParam = new NpgsqlParameter("CategoryName", category);
return _context.ByApplicationsReportModels
.FromSql(rawSql, categoryParam, advertisersParam);
}
Any ideas?

You might try changing where A.""Name"" in (#AdvertiserNames) to where (A.""Name"" in (#AdvertiserNames) or #AdvertiserNames = '').

Instead of concatenating your advertisers into a string, you could just pass an array of strings directly to your query:
var advertisersParam = new NpgsqlParameter("AdvertiserNames", advertisers));
In SQL, instead of using the x IN (#advertisers) construct, you would need to change to x = ANY (#advertisers).
Note: you would still need an additional clause if you want the check to pass when #advertisers is empty.

How to translate SQL to LINQ with individual field joins?

I have a SQL statement, that I want to implement in a .NET website project. I don't understand how to join in a particular field, as the fields aren't available when I just select from the table.
My SQL
SELECT *
FROM [vResidence] c
JOIN [vJobs] j on c.UID = j.UID
This is the LINQ I have tried, but I am stuck at the 'ON' part:
results = (from j in vJobs
join cr in vResidence on ??? )
When I try 'j.', the only option I get is 'equals'.

You can follow as this.connect to tables as JOIN use equals keyword
var result = from r in vResidence
join j vJobs on r.UID equals j.UID
select new {[yourcolnum]};

You can try this
var result = (from j in vJobs
join cr in vResidence
on j.UID equals cr.UID
select new {
...
}).ToList();

The Linq expression is the following:
from t1 in Table1
join t2 in Table2
on t1.ID equals t2.ID
The join clause on must be do in order: first the first table, then the second.
The keyword equals must be use.

Apart from the above Linq answers, we can do JOIN using Enumerable.Join extension with Lambda expressions. Try something like,
var result = vJobs.Join(vResidence, jb => new { jb.UID }, res => new { res.UID },
(jb, res) => new { jb, res })
.Select(x => x.jb) //Select the required properties (from both objects) with anonymous object or select left/right object
.ToList();
C# Fiddle with sample data.

SQL to LINQ with many joins

I'm struggling with a conversion of SQL query to LINQ.
Here is the SQL:
SELECT dbo.ORGANIZATION.ORGANIZATION_ID,
dbo.ORGANIZATION.ORGANIZATION_NAME,
dbo.PWR_ORGANIZATION_DIRECTORY.DIRECTORY_IDENTIFIER,
dbo.DETAIL_REQUIREMENT.DETAIL_ID,
dbo.DETAIL_REQUIREMENT.DETAIL_IDENTIFIER,
dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.DIRECTORY_ATTRIBUTE,
dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.ATTRIBUTE_VALIDATION,
dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.ATTRIBUTE_TRANSFORMATION,
dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.DETAIL_ACCESS
FROM dbo.ORGANIZATION INNER JOIN
dbo.DETAIL_REQUIREMENT ON dbo.ORGANIZATION.ORGANIZATION_ID = dbo.DETAIL_REQUIREMENT.ORGANIZATION_ID INNER JOIN
dbo.PWR_ORGANIZATION_DIRECTORY INNER JOIN
dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING ON dbo.PWR_ORGANIZATION_DIRECTORY.ORGANIZATION_ID = dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.ORGANIZATION_ID AND
dbo.PWR_ORGANIZATION_DIRECTORY.DIRECTORY_TYPE_ID = dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.DIRECTORY_TYPE_ID AND
dbo.PWR_ORGANIZATION_DIRECTORY.DIRECTORY_ID = dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.DIRECTORY_ID ON
dbo.DETAIL_REQUIREMENT.DETAIL_ID = dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.DETAIL_ID AND
dbo.ORGANIZATION.ORGANIZATION_ID = dbo.PWR_ORGANIZATION_DIRECTORY_MAPPING.ORGANIZATION_ID
WHERE dbo.ORGANIZATION.ORGANIZATION_ID = 0 AND
dbo.PWR_ORGANIZATION_DIRECTORY.DIRECTORY_ID = 1 AND
dbo.PWR_ORGANIZATION_DIRECTORY.DIRECTORY_TYPE_ID = 1
And this is how I started but got confused when there were two and three joins between tables:
var megaFetch = from org in context.Organizations
join detReq in context.DetailRequirements on org.OrganizationId equals detReq.OrganizationId
join detMap in context.OrganizationDirectoryMappings on org.OrganizationId equals detMap.OrganizationId &&
Can someone guide me here?
Thanks.

If you need to join a tables in more than one column, create anonymous types with both sides having same number of fields. It should be like;
new {col1 = x.col1, col2 = x.col2, ...} equals new { col1 = y.col1, col2 = y.col2, ...}

LINQ2SQL - More Questions on when a Cross join with where clause is emitted instead of Inner Join

This is a two part question and for education purposes rather than trying to find a solution to a problem.
I've seen this already and realize that it's very similar to my question
LINQ2SQL - Cross join emitted when I want inner join
But I am hoping for more information from you LINQ and SQL gurus as to why the cross join is created instead of inner join in LINQ2SQL. Additionally, can someone explain how SQL Server decides on the execution plan (or link to further information) since both of these queries generate the same plan? From what I understand, this means that the performance of the queries are the same.
I've created a small example that runs two LINQ expressions on my database that generates these two different SQL queries.
For those who don't want to bother, here's my example db diagram:
http://dl.dropbox.com/u/13256/Screen%20shot%202011-03-16%20at%2011.41.56%20AM.png
Here are the two queries:
Cross Join with Where Clause
var q = from item in context.Items
join i_mem in context.Memberships on new { item_id = item.ID, user_id =
current_user_id.Value } equals new { item_id = i_mem.RelatedItemID, user_id =
i_mem.RelatedUserID } into sq_i_m
from im in sq_i_m.DefaultIfEmpty()
join i_cat in context.Categories on item.RelatedCategoryID equals i_cat.ID
into sq_i_cat
from proj in sq_i_cat
select item;
Inner Join
from item in context.Items
join i_mem in context.Memberships on
new { item_id = item.ID, user_id = current_user_id.Value }
equals
new { item_id = i_mem.RelatedItemID, user_id = i_mem.RelatedUserID }
into sq_i_m
from im in sq_i_m.DefaultIfEmpty()
join i_cat in context.Categories on item.RelatedCategoryID equals i_cat.ID
select item
And here is the test program if you'd like to see for yourself.
Thanks for everyone's help.
Mustafa

They are the same thing, so it does not matter which LINQ2SQL emits.
An inner join is logically equivalent to a cross join with a where clause filter equivalent to the on of the inner join clause.
That's why Sql Server generates the same query plan.
To be clear, the inner join:
Select f1
From T1 inner join T2 on T1.k = T2.k
where T1.f2 like 'X%'
Is the same as the cross join:
Select f1
From T1 cross join T2
where T1.k = T2.k
and T1.f2 like 'X%'
is the same as old-style SQL:
Select f1
From T1, T2
where T1.k = T2.k
and T1.f2 like 'X%'

Lets say you have a datacontext called MyDataContext.
using(MyDataContext db = new MyDataContext())
{
var q = db.Items.Where(x=> x.Categories.Name == "myCategory").Select(x=> x);
}
This is a very simple example, but you didn't need to write out a join or a subquery in TSQL syntax. (I hate writing TSQL).