I've been trying for a while to insert on MongoDB using only records with no success.
My problem is that I want to create a simple insert function which I send a generic type and it is inserted into the database.
Like so.
let insert (value: 'a) =
let collection = MongoClient().GetDatabase("db").GetCollection<'a> "col"
collection.InsertOne value
From this function, I tried inserting the following records.
// Error that it can't set the Id
type t1 = {
Id: ObjectId
Text: string
}
// Creates the record perfectly but doesn't generate a new Id
type t2 = {
Id: string
Text: string
}
// Creates the record and autogenerates the Id but doesn't insert the Text, and there are two Ids (_id, Id#)
type t3 = {
mutable Id: ObjectId
Text: string
}
// Creates the record and autogenerates the Id but for every property it generates two on MongoDB (_id, Id#, Text, Text#)
type t4 = {
mutable Id: ObjectId
mutable Text: string
}
So does anyone can think of a solution for this or am I stuck having to use a class.
// Works!!!
type t5() =
member val Id = ObjectId.Empty with get, set
member val Name = "" with get, set
Also, does anyone has any Idea of why when the C# MongoDB library translates the mutable he gets the property with the # at the end?
I would be fine with having all my properties set as mutable, although this wouldn't be my first choice, having he create multiple properties on the DB is quite bad.
You could try annotating your records with CLIMutable (and no mutable fields).
The #s end up in the DB because MongoDB using reflection and F# implementing mutable with backing fields fieldName#
Related
i would like to kmow the advantages of using virtuals in mongoose while establishing relationship. Will it result in faster retrival of information from DB
Virtuals are additional fields for a given model. Their values can be set manually or automatically with defined functionality. A common virtual property is the full name of a person, composed of user’s first and last name.
virtual properties don’t get persisted in the database. They only exist logically and are not written to the document’s collection.
Example
Mongoose Schema
The user schema has two properties indicating the user’s first and last name: first and last.
// define user schema
var userSchema = new Schema({
first: String,
last: String
});
// compile our model
var User = mongoose.model('User', userSchema);
// create a document
var mentalist = new User({
first: 'Patrick',
last: 'Jane'
});
Assume we want to get the full name of a mentalist, we can do this manually appending the first to last property:
console.log(mentalist.first + ' ' + mentalist.last); // Patrick Jane
Define a Virtual Property
Actually, there is a better way of getting the full name of a user: virtual fields. With virtuals, you benefit of writing the name concatenation mess only once.
Mongoose splits the definiton of virtual fields into GET and SET methods.
Get Method
The virtuals get method is a function returning a the virtual value. You can do complex processing or just concatenate single document field values.
userSchema.virtual('fullname').get(function() {
return this.first + ' ' + this.last;
});
The code example above just concatenates the first and last property values. With that, the virtual fullname property now will print the same output as above:
console.log(mentalist.fullname); // Patrick Jane
Set Method
setter methods are useful to split strings or do other operations. Define a virtual setter by passing a proper function and execute your desired processing. The example below splits the passed name variable at any whitespace.
userSchema.virtual('fullname').set(function (name) {
var split = name.split(' ');
this.first = split[0];
this.last = split[1];
});
The first part of name is assigned to the first and the second part to the last property. This set method will override the previous model values and assign the ones we pass as fullname property.
var humor = new User({
first: '',
last: ''
});
humor.fullname = 'Kimball Cho';
console.log(humor.first); // Kimball
console.log(humor.last); // Cho
Queries and Field Selection
Virtuals are NOT available for document queries or field selection. Only non-virtual properties work for queries and field selections.
As you see, virtual properties aren’t static model properties. They
are additional model functions returning values based on the default
schema fields.
In my CRUD Rest Service I do an insert into a DB and want to respond to the caller with the created new record. I am looking for a nice way to convert the map to json.
I am running on ballerina 0.991.0 and using a postgreSQL.
The return of the Update ("INSERT ...") is a map.
I tried with convert and stamp but i did not work for me.
import ballerinax/jdbc;
...
jdbc:Client certificateDB = new({
url: "jdbc:postgresql://localhost:5432/certificatedb",
username: "USER",
password: "PASS",
poolOptions: { maximumPoolSize: 5 },
dbOptions: { useSSL: false }
}); ...
var ret = certificateDB->update("INSERT INTO certificates(certificate, typ, scope_) VALUES (?, ?, ?)", certificate, typ, scope_);
// here is the data, it is map<anydata>
ret.generatedKeys
map should know which data type it is, right?
then it should be easy to convert it to json like this:
{"certificate":"{certificate:
"-----BEGIN
CERTIFICATE-----\nMIIFJjCCA...tox36A7HFmlYDQ1ozh+tLI=\n-----END
CERTIFICATE-----", typ: "mqttCertificate", scope_: "QARC", id_:
223}"}
Right now i do a foreach an build the json manually. Quite ugly. Maybe somebody has some tips to do this in a nice way.
It cannot be excluded that it is due to my lack of programming skills :-)
The return value of JDBC update remote function is sql:UpdateResult|error.
The sql:UpdateResult is a record with two fields. (Refer https://ballerina.io/learn/api-docs/ballerina/sql.html#UpdateResult)
UpdatedRowCount of type int- The number of rows which got affected/updated due to the given statement execution
generatedKeys of type map - This contains a map of auto generated column values due to the update operation (only if the corresponding table has auto generated columns). The data is given as key value pairs of column name and column value. So this map contains only the auto generated column values.
But your requirement is to get the entire row which is inserted by the given update function. It can’t be returned with the update operation if self. To get that you have to execute the jdbc select operation with the matching criteria. The select operation will return a table or an error. That table can be converted to a json easily using convert() function.
For example: Lets say the certificates table has a auto generated primary key column name ‘cert_id’. Then you can retrieve that id value using below code.
int generatedID = <int>updateRet.generatedKeys.CERT_ID;
Then use that generated id to query the data.
var ret = certificateDB->select(“SELECT certificate, typ, scope_ FROM certificates where id = ?”, (), generatedID);
json convertedJson = {};
if (ret is table<record {}>) {
var jsonConversionResult = json.convert(ret);
if (jsonConversionResult is json) {
convertedJson = jsonConversionResult;
}
}
Refer the example https://ballerina.io/learn/by-example/jdbc-client-crud-operations.html for more details.?
I am using GroupBy in my LINQ queries. My query is working fine, except my foreign key objects are missing. Then, I tried to add Include in my query. Following is my code:
public ActionResult GetEmployees()
{
var Emloyees = db.Employees.AsQueryable();
Emloyees.GroupBy(e=> new {e.JobTitleId, e.GenderId})
.Select(tr => new MyObject
SalaryTotal = tr.Sum(r=>r.Salary)
}).Include(tr=>tr.JobTitle).Include(tr=>tr.Gender).ToList();
}
I am getting this exception:
The result type of the query is neither an EntityType nor a CollectionType with an entity element type. An Include path can only be specified for a query with one of these result types.
I tried to add it before GroupBy and directly in db.Employees.AsQueryable(), but nothing worked. What am I doing wrong?
The problem is that you are doing a projection with the .Select(...), after which your includes cannot be resolved. The result of that query will be a list MyObject, which does not work for includes that are actually on Employee.
So Try it like this:
Emloyees
.GroupBy(e=> new {e.JobTitleId, e.GenderId})
.Select(tr => new MyObject {
SalaryTotal = tr.Sum(r=>r.Salary),
JobTitle = tr.FirstOrDefault().JobTitle,
Gender = tr.FirstOrDefault().Gender
}).ToList();
You will have to extend MyObject with 2 additional properties, but the result of your query will be what you want (I assume).
I am using EF Framework to retrieve the data from SQL DB.
Sub Request Table looks like below:
In this table "org_assigneddept" is foreign key to another Department Table.
I have list of Departments as Input and I want to retrieve only those rows from DB whose org_assigneddept is matching the list.
Please find my whole code:-
private List<EventRequestDetailsViewModel> GetSummaryAssignedDeptEventRequests(List<EmpRoleDeptViewModel> vmDept)
{
List<EventRequestDetailsViewModel> vmEventRequestDeptSummary = new List<EventRequestDetailsViewModel>();
RequestBLL getRequestBLL = new RequestBLL();
Guid subRequestStatusId = getRequestBLL.GetRequestStatusId("Open");
using (var ctxGetEventRequestSumm = new STREAM_EMPLOYEEDBEntities())
{
vmEventRequestDeptSummary = (from ers in ctxGetEventRequestSumm.SubRequests
where vmDept.Any(dep=>dep.DeptId == ers.org_assigneddept)
select new EventRequestDetailsViewModel
{
SubRequestId = ers.org_subreqid
}).ToList();
}
}
It is giving the following error at the LINQ Query level:-
System.NotSupportedException: 'Unable to create a constant value of
type 'Application.Business.DLL.EmpRoleDeptViewModel'. Only primitive
types or enumeration types are supported in this context.'
Please let me know as how can I achieve the result
You cannot pass the department VMs to SQL, it doesn't know what those are.
// Extract the IDs from the view models.. Now a list of primitive types..
var departmentIds = vmDept.Select(x => x.DeptId).ToList();
then in your select statement...
..
where departmentIds.Contains(id=> id == ers.org_assigneddept)
..
Can anyone explain the behavior I am seeing in the minimal code example below? It seems that for a given field or property, the same two instances of the Entry class are being reused in each iteration of the LINQ to SQL query, even though I use the new operator. The same problem does not show up for LINQ to objects queries. I created a C# console application project using .NET Framework 4 and connecting to a SQL Server 2005 Enterprise database.
public class Set
{
public Entry Field;
public Entry Property { get; set; }
}
public class Entry
{
public int ID;
public string Name { get; set; }
}
class Program
{
static void Main(string[] args)
{
var dc = new DataClasses1DataContext(); // just create a simple dbml with some table from some database
var resultQuery = (
from x in dc.SomeTable
select new Set()
{
Field = new Entry(),
Property = new Entry()
}
);
var sets = resultQuery.ToArray();
Test(sets);
var source = Enumerable.Range(0, 10);
var sourceQuery = (
from x in source
select new Set()
{
Field = new Entry(),
Property = new Entry()
}
);
var sets2 = sourceQuery.ToArray();
Test(sets2);
}
static void Test(Set[] sets)
{
var f = sets[0].Field;
Console.WriteLine(sets.All(x => object.Equals(x.Field, f)));
var p = sets[0].Property;
Console.WriteLine(sets.All(x => object.Equals(x.Property, p)));
Console.Writeline(sets.Length);
Console.WriteLine(object.Equals(f, p));
Console.WriteLine();
}
}
The output of Test() for the LINQ to SQL query is
True
True
1362
False
which indicates that for all of the Set objects produced, all the Field members point to the same single Entry instance and all the Property members point to the same single Entry instance. I.e., the same instance is reused for a respective member in every iteration of the query.
The output of Test() for the LINQ to objects query is
False
False
10
False
which indicates that a new distinct instance is created in each iteration of the query.
Is the LINQ to SQL behavior expected or a bug? Does anyone know if this happens with the Entity Framework?
I don't know if this is a bug or if and why this is expected in LINQ to SQL. I can only answer your last question if that also happens with Entity Framework.
The answer is: No.
With EF you have to use object initializer syntax though when you instantiate the Entry objects. Using the default constructor leads to an exception:
var resultQuery = (
from x in dc.SomeTable
select new Set
{
Field = new Entry { Name = "X" },
Property = new Entry { Name = "X" }
}
);
It doesn't matter how you initialize. Using the code above (and with 4 rows in a small test table) I get this output with your test program:
False
False
4
False
False
False
10
False
It looks that there is a big difference between LINQ to SQL and Entity Framework regarding object materialization during projections.
(I've tested with EF 4.1/DbContext.)
Edit
If I take the modified query in my code snippet above also for your LINQ to SQL query and watch the generated SQL I get the following:
SELECT NULL AS [EMPTY]
FROM [dbo].[SomeTable] AS [t0]
Whereas the same with LINQ to Entites creates this query:
SELECT
1 AS [C1],
N'X' AS [C2],
N'X' AS [C3]
FROM [dbo].[SomeTable] AS [Extent1]
My interpretation is that LINQ to SQL parses the projection code and queries only columns for property values which depend on the "row variable" x. All other properties are filled on the client when the objects get materialized. If an object does not depend on a column value at all, LINQ to SQL creates a single constant object and reuses it in the whole result collection.
In constrast to this Entity Framework also sends constant values (independent of x) to the database server. The values get send back to the client and EF treats those values as if they were column values and updates the properties of the objects in the projection.
This leads also to the big difference that something like this...
Random random = new Random();
var resultQuery = (
from x in dc.SomeTable
select new Set
{
Field = new Entry { ID = random.Next() },
Property = new Entry { Name = "X" }
}
);
...works in LINQ to SQL because apparently the random function value (which is independent of x) is evaluated on the client and then assigned to the property. But EF wants to translate the right side of the property assignment into SQL and send it as SQL fragment to the database server - which fails and leads to the infamous "...cannot translate into store expression..." exception.
Edit 2
BTW: The last code snippet above still creates only a single Field instance in the whole collection: random.Next() is only evaluated once (and also the constructor of Entry is only called once for the Field object). This now is indeed confusing because writing such code one would expect that you want to have a random value for each row returned from the database. It's not the case.