From the Hasura documentation is not possible to order by nested array relationships, the thing is I'm using that relation to get only one element from the array (e.g. the latest entry in that table). There is any way to transform that array (with one element) into an object to be able to perform order by in the root query?. Example:
query GetMachinesQuery {
machines {
machine_id
machine_detail
last_upgrade: upgrades(order_by: { created_at: desc }, limit: 1) {
upgrade_state {
updated_at
status
}
}
}
}
Do I have any way to sort the root query by any of the fields (e.g. status) present in the last_upgrade? The possible workaround is create a view (doing the joins to get latest upgrade info for each machine) and then I can use an object relationship, any other alternatives with hasura?
Thank you !
In our RethinkDB database, we have a table for orders, and a separate table that stores all the order items. Each entry in the OrderItems table has the orderId of the corresponding order.
I want to write a query that gets all SHIPPED order items (just the items from the OrderItems table ... I don't want the whole order). But whether the order is "shipped" is stored in the Order table.
So, is it possible to write a query that filters the OrderItems table based on the "shipped" value for the corresponding order in the Orders table?
If you're wondering, we're using the JS version of Rethinkdb.
UPDATE:
OK, I figured it out on my own! Here is my solution. I'm not positive that it is the best way (and certainly isn't super efficient), so if anyone else has ideas I'd still love to hear them.
I did it by running a .merge() to create a new field based on the Order table, then did a filter based on that value.
A semi-generalized query with filter from another table for my problem looks like this:
r.table('orderItems')
.merge(function(orderItem){
return {
orderShipped: r.table('orders').get(orderItem('orderId')).pluck('shipped') // I am plucking just the "shipped" value, since I don't want the entire order
}
})
.filter(function(orderItem){
return orderItem('orderShipped')('shipped').gt(0) // Filtering based on that new "shipped" value
})
it will be much easier.
r.table('orderItems').filter(function(orderItem){
return r.table('orders').get(orderItem('orderId'))('shipped').default(0).gt(0)
})
And it should be better to avoid result NULL, add '.default(0)'
It's probably better to create proper index before any finding. Without index, you cannot find document in a table with more than 100,000 element.
Also, filter is limit for only primary index.
A propery way is to using getAll and map
First, create index:
r.table("orderItems").indexCreate("orderId")
r.table("orders").indexCreate("shipStatus", r.row("shipped").default(0).gt(0))
With that index, we can find all of shipper order
r.table("orders").getAll(true, {index: "shipStatus"})
Now, we will use concatMap to transform the order into its equivalent orderItem
r.table("orders")
.getAll(true, {index: "shipStatus"})
.concatMap(function(order) {
return r.table("orderItems").getAll(order("id"), {index: "orderId"}).coerceTo("array")
})
I've the following Entity Model : Employee has a Company and a Company has Employees.
When using the Include statement like below:
var query = context.Employees.Include(e => e.Company);
query.Dump();
All related data is retrieved from the database correctly. (Using LEFT OUTER JOIN on Company table)
The problem is hat when I use the GroupBy() from System.Linq.Dynamic to group by Company.Name, the Employees are missing the Company data because the Include is lost.
Example:
var groupByQuery = query.GroupBy("new (Company.Name as CompanyName)", "it");
groupByQuery.Dump();
Is there a way to easily retrieve the applied Includes on the 'query' as a string collection, so that I can include them in the dynamic GroupBy like this:
var groupByQuery2 = query.GroupBy("new (Company, Company.Name as CompanyName)", "it");
groupByQuery2.Dump();
I thought about using the ToString() functionality to get the SQL Command like this:
string sql = query.ToString();
And then use RegEx to extract all LEFT OUTER JOINS, but probably there is a better solution ?
if you're creating the query in the first place - I'd always opt to save the includes (and add to them if you're making a composite query/filtering).
e.g. instead of returning just 'query' return new QueryContext {Query = query, Includes = ...}
I'd like to see a more elegant solution - but I think that's your best bet.
Otherwise you're looking at expression trees, visitors and all those nice things.
SQL parsing isn't that straight either - as queries are not always that simple (often a combo of things etc.).
e.g. there is a `span' inside the query object (if you traverse a bit) which seems to be holding the 'Includes' but it's not much help.
db.AdDetails.Where( u => u.OwnerGUID == CurrentUserProviderKey)
I have an adDetails table that has an OwnerGUID field.
I want to pull out only ad details that belong to the currenly logged in user.
My query does not show any where clauses in the SQL when I look at it in the debugger.
Can someone help me figure out what is wrong with my statement and if all rows in the table will be brought back then all 10K records put though a where on the webserver?
I am really new to this.
Using the Where extension method will filter down the results.
Queries in Entity Framweork are not executed until you iterate over them. If you do:
var query = db.Where(u => u.OwnerGUID == key);
This does not execute the query. When you do the following:
var list = list.ToList();
OR
foreach( var item in query) { ... }
That is when the query will be executed in SQL. The results should be filtered with your WHERE clause at this point.
Let's say I have an Order table which has a FirstSalesPersonId field and a SecondSalesPersonId field. Both of these are foreign keys that reference the SalesPerson table. For any given order, either one or two salespersons may be credited with the order. In other words, FirstSalesPersonId can never be NULL, but SecondSalesPersonId can be NULL.
When I drop my Order and SalesPerson tables onto the "Linq to SQL Classes" design surface, the class builder spots the two FK relationships from the Order table to the SalesPerson table, and so the generated Order class has a SalesPerson field and a SalesPerson1 field (which I can rename to SalesPerson1 and SalesPerson2 to avoid confusion).
Because I always want to have the salesperson data available whenever I process an order, I am using DataLoadOptions.LoadWith to specify that the two salesperson fields are populated when the order instance is populated, as follows:
dataLoadOptions.LoadWith<Order>(o => o.SalesPerson1);
dataLoadOptions.LoadWith<Order>(o => o.SalesPerson2);
The problem I'm having is that Linq to SQL is using something like the following SQL to load an order:
SELECT ...
FROM Order O
INNER JOIN SalesPerson SP1 ON SP1.salesPersonId = O.firstSalesPersonId
INNER JOIN SalesPerson SP2 ON SP2.salesPersonId = O.secondSalesPersonId
This would make sense if there were always two salesperson records, but because there is sometimes no second salesperson (secondSalesPersonId is NULL), the INNER JOIN causes the query to return no records in that case.
What I effectively want here is to change the second INNER JOIN into a LEFT OUTER JOIN. Is there a way to do that through the UI for the class generator? If not, how else can I achieve this?
(Note that because I'm using the generated classes almost exclusively, I'd rather not have something tacked on the side for this one case if I can avoid it).
Edit: per my comment reply, the SecondSalesPersonId field is nullable (in the DB, and in the generated classes).
The default behaviour actually is a LEFT JOIN, assuming you've set up the model correctly.
Here's a slightly anonymized example that I just tested on one of my own databases:
class Program
{
static void Main(string[] args)
{
using (TestDataContext context = new TestDataContext())
{
DataLoadOptions dlo = new DataLoadOptions();
dlo.LoadWith<Place>(p => p.Address);
context.LoadOptions = dlo;
var places = context.Places.Where(p => p.ID >= 100 && p.ID <= 200);
foreach (var place in places)
{
Console.WriteLine(p.ID, p.AddressID);
}
}
}
}
This is just a simple test that prints out a list of places and their address IDs. Here is the query text that appears in the profiler:
SELECT [t0].[ID], [t0].[Name], [t0].[AddressID], ...
FROM [dbo].[Places] AS [t0]
LEFT OUTER JOIN (
SELECT 1 AS [test], [t1].[AddressID],
[t1].[StreetLine1], [t1].[StreetLine2],
[t1].[City], [t1].[Region], [t1].[Country], [t1].[PostalCode]
FROM [dbo].[Addresses] AS [t1]
) AS [t2] ON [t2].[AddressID] = [t0].[AddressID]
WHERE ([t0].[PlaceID] >= #p0) AND ([t0].[PlaceID] <= #p1)
This isn't exactly a very pretty query (your guess is as good as mine as to what that 1 as [test] is all about), but it's definitively a LEFT JOIN and doesn't exhibit the problem you seem to be having. And this is just using the generated classes, I haven't made any changes.
Note that I also tested this on a dual relationship (i.e. a single Place having two Address references, one nullable, one not), and I get the exact same results. The first (non-nullable) gets turned into an INNER JOIN, and the second gets turned into a LEFT JOIN.
It has to be something in your model, like changing the nullability of the second reference. I know you say it's configured as nullable, but maybe you need to double-check? If it's definitely nullable then I suggest you post your full schema and DBML so somebody can try to reproduce the behaviour that you're seeing.
If you make the secondSalesPersonId field in the database table nullable, LINQ-to-SQL should properly construct the Association object so that the resulting SQL statement will do the LEFT OUTER JOIN.
UPDATE:
Since the field is nullable, your problem may be in explicitly declaring dataLoadOptions.LoadWith<>(). I'm running a similar situation in my current project where I have an Order, but the order goes through multiple stages. Each stage corresponds to a separate table with data related to that stage. I simply retrieve the Order, and the appropriate data follows along, if it exists. I don't use the dataLoadOptions at all, and it does what I need it to do. For example, if the Order has a purchase order record, but no invoice record, Order.PurchaseOrder will contain the purchase order data and Order.Invoice will be null. My query looks something like this:
DC.Orders.Where(a => a.Order_ID == id).SingleOrDefault();
I try not to micromanage LINQ-to-SQL...it does 95% of what I need straight out of the box.
UPDATE 2:
I found this post that discusses the use of DefaultIfEmpty() in order to populated child entities with null if they don't exist. I tried it out with LINQPad on my database and converted that example to lambda syntax (since that's what I use):
ParentTable.GroupJoin
(
ChildTable,
p => p.ParentTable_ID,
c => c.ChildTable_ID,
(p, aggregate) => new { p = p, aggregate = aggregate }
)
.SelectMany (a => a.aggregate.DefaultIfEmpty (),
(a, c) => new
{
ParentTableEntity = a.p,
ChildTableEntity = c
}
)
From what I can figure out from this statement, the GroupJoin expression relates the parent and child tables, while the SelectMany expression aggregates the related child records. The key appears to be the use of the DefaultIfEmpty, which forces the inclusion of the parent entity record even if there are no related child records. (Thanks for compelling me to dig into this further...I think I may have found some useful stuff to help with a pretty huge report I've got on my pipeline...)
UPDATE 3:
If the goal is to keep it simple, then it looks like you're going to have to reference those salesperson fields directly in your Select() expression. The reason you're having to use LoadWith<>() in the first place is because the tables are not being referenced anywhere in your query statement, so the LINQ engine won't automatically pull that information in.
As an example, given this structure:
MailingList ListCompany
=========== ===========
List_ID (PK) ListCompany_ID (PK)
ListCompany_ID (FK) FullName (string)
I want to get the name of the company associated with a particular mailing list:
MailingLists.Where(a => a.List_ID == 2).Select(a => a.ListCompany.FullName)
If that association has NOT been made, meaning that the ListCompany_ID field in the MailingList table for that record is equal to null, this is the resulting SQL generated by the LINQ engine:
SELECT [t1].[FullName]
FROM [MailingLists] AS [t0]
LEFT OUTER JOIN [ListCompanies] AS [t1] ON [t1].[ListCompany_ID] = [t0].[ListCompany_ID]
WHERE [t0].[List_ID] = #p0