I am using sails to build an API, one of my function needs to get columns from my PGSQL database. My SQL request is working when I test it in PGadmin, it looks like this :
SELECT "user".id, "user".picture, "user".first_name, "trophe".trophe FROM "user" INNER JOIN "trophe" ON "trophe".user = "user".id WHERE "trophe".foot = 1
When I transcript this request in my sails API, it looks like this :
getHommeAndChevre: function (req, res) {
console.log(req.param("id"));
Trophe.query("SELECT 'user'.id, 'user'.picture, 'user'.first_name, 'trophe'.trophe FROM 'user' INNER JOIN 'trophe' ON 'trophe'.user = 'user'.id WHERE 'trophe'.foot ="+req.param('id'), function(err,trophes){
if(!trophes) {return res.status(400).end();}
if(trophes){
_each(trophes, function(trophe){
if (trophe.trophe == 0) {var chevre = trophe};
if (trophe.trophe == 1) { var homme = trophe};
})
return res.status(200).json({chevre: chevre, homme: homme})
}
});
}
However whatever I do the Trophe.query always returned undefined. What could be wrong here ?
Your return is outside the callback , so you return the value before the end of the query.
_each(trophes, function(trophe, index){
if (trophe.trophe == 0) {var chevre = trophe};
if (trophe.trophe == 1) { var homme = trophe};
if (index == trophes.length - 1) //End of the loop
return res.status(200).json({chevre: chevre, homme: homme});
})
Use double quotes for identifiers
Trophe.query('SELECT "user".id, "user".picture, "user".first_name, ...
Related
I have a function doing a complicated Where query on my db context and then applies another transformation passed to it:
static IQueryable<T> Query<T>(Func<IQueryable<ServicesData>, IQueryable<T>> f, string path1 = null, string path2 = null, string path3 = null, string path4 = null, string path5 = null) {
try {
using (var dbc = new MyDbContext() ) {
var res = dbc.ServicesData
.Where(sd =>
(path1 == null || (path1.Contains("%") || path1.Contains("_") ? EF.Functions.Like(sd.Path1, path1) : sd.Path1 == path1))
&& (path2 == null || (path2.Contains("%") || path2.Contains("_") ? EF.Functions.Like(sd.Path2, path2) : sd.Path2 == path2))
&& (path3 == null || (path3.Contains("%") || path3.Contains("_") ? EF.Functions.Like(sd.Path3, path3) : sd.Path3 == path3))
&& (path4 == null || (path4.Contains("%") || path4.Contains("_") ? EF.Functions.Like(sd.Path4, path4) : sd.Path4 == path4))
&& (path5 == null || (path5.Contains("%") || path5.Contains("_") ? EF.Functions.Like(sd.Path5, path5) : sd.Path5 == path5)));
return f(res.ToList().AsQueryable());
//return f(res).ToList().AsQueryable();
}
} catch (Exception ex_) {
return VList<T>.Empty.AsQueryable();
}
}
This is used ie like this:
IQueryable<int> Int1InLastHour(IQueryable<ServicesData> input) {
var lastHour = DateTimeOffset.Now.AddHours(-1).ToUnixTimeMilliseconds();
return input
.Where(v => (v.Time <= lastHour) && (v.Int1 is object))
.Select(v => v.Int1.Value);
}
var lastHourProcessTime = Query(Int1InLastHour, "Publisher", "%", "ItemProcessTime").Sum();
This works, however since I call res.ToList() before calling f the linq in f is done in memory and not on the DB SQL
If I try to replace f(res.ToList().AsQueryable()) with f(res).ToList().AsQueryable() I get an exception:
{"Processing of the LINQ expression '[EntityShaperExpression][ServicesData]' by 'RelationalProjectionBindingExpressionVisitor' failed. This may indicate either a bug or a limitation in EF Core. See https://go.microsoft.com/fwlink/?linkid=2101433 for more detailed information."}
Is there any way for me to solve this ? can I somehow pass the query (Func<IQueryable<ServicesData>, IQueryable<T>>) and then combine it to the query in Query before excecuting it on the dbc ?
A few issues. You can split the querying to break down your results, but the scope of your DbContext needs to be at the outermost point of the chain, not inside the inner-most:
This here:
static IQueryable<T> Query<T>(Func<IQueryable<ServicesData>, IQueryable<T>> f, string path1 = null, string path2 = null, string path3 = null, string path4 = null, string path5 = null) {
try {
using (var dbc = new MyDbContext() ) { // DbContext should not be scoped here...
var res = dbc.ServicesData
As the simplest re-factor:
static IQueryable<T> Query<T>(MyDbContext dbc, Func<IQueryable<ServicesData>, IQueryable<T>> f, string path1 = null, string path2 = null, string path3 = null, string path4 = null, string path5 = null) {
try
{
var res = dbc.ServicesData.AsQueryable();
if(path1 != null)
if(path1.Contains("%") || path1.Contains("_"))
res = res.Where(EF.Functions.Like(sd.Path1, path1));
else
res = res.Where(sd.Path1 == path1);
// Repeat for Path 2 - 5 ....
return f(res);
}
catch (Exception ex_)
{
return VList<T>.Empty.AsQueryable();
}
}
Firstly, we pass in the DbContext. If the context is scoped here, the list must be materialized before being returned. The goal is to allow callers to further reduce the expression before executing the list. This means the DbContext needs to be scoped outside of this initial generation and passed in. With IoC containers managing lifetime scope you can bypass this if the DbContext is injected and scoped to a Request or common lifetime scope.
The next improvement suggestion is to move the conditional checks for the parameters out of the Linq and into regular conditions so that the Like / Equals check will only be added if the condition was provided. This will result in simpler, faster SQL being run on the server.
So the end result would look something like:
using (var dbContext = new MyDbContext())
{
var lastHourProcessTime = Query(dbContext, Int1InLastHour, "Publisher", "%", "ItemProcessTime").Sum();
}
I sort of get where you're trying to go here, but abstracting expressions from EF is bound to lead to confusing code and still prone to limitations and bugs. IMO keeping it simpler generally leads to less issues, but give this a go and see if it gets you closer.
I am using this query:
var result = from r in db.Registrations
join u in db.UserTypes on r.UserTypeId equals u.UserTypeId
where r.Email.ToLower()==model.LoginEmail.ToLower() && r.Password.ToLower() == model.Password.ToLower()
select new { r,u};
Here how can I check that if no record is found? If so, then
if(result == null)
// no record found
else
// record found
You can use Any or Count extension method:
if(!result.Any())
///norecord found
else
//record found
Using Count would be:
if(result.Count()==0)
///norecord found
else
//record found
First what you assign to a result is just IQueryable so it's query and you need to execute it first. So I suggest renaming it to query and then do it like this:
var query= from r in db.Registrations
join u in db.UserTypes on r.UserTypeId equals u.UserTypeId
where r.Email.ToLower()==model.LoginEmail.ToLower() && r.Password.ToLower() == model.Password.ToLower();
select new { r,u};
var result = query.FirstOrDefault(); // gives first result or null
if (result == null) {
// no record
} else {
// record found and is in result
}
I'm using WCF RIA in a Lightswitch project to create some query results. This query brings back all results regardless. I cannot make it filter the records based on the parameter passed (string Town).
public IQueryable<Enquiries> TestQuery(string Town)
{
List<Enquiries> riaenqs = new List<Enquiries>();
var enqs = this.Context.ClientEnquiries
.Include("Client")
.Include("Client.Town")
.OrderBy(enq => enq.Id);
if (Town != null)
{
enqs.Where(enq => enq.Client.Town.TownName == Town);
}
foreach (ClientEnquiry item in enqs.ToList())
{
Enquiries enq = new Enquiries();
enq.Id = item.Id;
enq.ClientName = item.Client.FirstName + " " + item.Client.Surname;
enq.Town = item.Client.Town != null ? item.Client.Town.TownName : null;
riaenqs.Add(enq);
}
return riaenqs.AsQueryable();
}
During debugging I can see that the Town is correctly populated and I can see that the query is built accordingly if Town is not null. However, when I hit the foreach statement where the linq to ef query is executed I always get all the results. I just cannot figure out where I'm slipping up.
The LINQ methods like the Where do not modify the collection/expression but always returning a new one.
So you need to reassign the result of the Where to your original variable enqs:
if (Town != null)
{
enqs = enqs.Where(enq => enq.Client.Town.TownName == Town);
}
I am getting a null refrence exception when im filtering EF but I am absolultely clueless.
public IEnumerable<TonalityBatchModel> GetTonalityBatch(int briefID)
{
try
{
var brief = NeptuneUnitOfWork.Briefs.FindWhere(b => b.ID == briefID).FirstOrDefault();
if (brief != null && brief.TonalityCriteria != null)
{
return brief.TonalityCriteria.TonalityBatches
.Select(b => new TonalityBatchModel()
{
BriefID = b.BriefID,
Status = b.TonalityCriteria.IsActive == true ?"Active":"Ended",
BatchID = b.ID,
CompetitorID = b.BriefCompetitorID,
Competitor = brief.BriefCompetitors.Where(i=>i.ID == b.BriefCompetitorID).Select(c=>c.Organisation.Name).First(),
Size = b.BatchSize,
StartDate = b.StartDate,
EndDate = b.EndDate,
IsPublished = b.Lookup_TonalityBatchStatus.ID == (int)TonalityBatchStatus.Published?"Yes":"No",
IsCompleted = b.Lookup_TonalityBatchStatus.ID == (int)TonalityBatchStatus.Completed ? "Yes" : "No",
IsAssigned = b.Lookup_TonalityBatchStatus.ID == (int)TonalityBatchStatus.Allocated ? "Yes" : "No",
ImportantCount = b.TonalityItems.Count(i=> i.IsImportant),
ArticlesCount = b.TonalityItems.Count,
FavourableCount = b.TonalityItems.Count(i => i.Lookup_TonalityScoreTypes.ID ==(int)TonalitySourceType.Favourable),
UnfavourableCount = b.TonalityItems.Count(i => i.Lookup_TonalityScoreTypes.ID ==(int)TonalitySourceType.Unfavourable),
NeutralCount = b.TonalityItems.Count(i => i.Lookup_TonalityScoreTypes.ID ==(int)TonalitySourceType.Neutral)
}).ToList();
}
return new List<TonalityBatchModel>();
}
catch (Exception ex)
{
Logger.Error(ex);
throw;
}
}
You'll need to reduce your query to a simpler query, and then start building it back up again until the NullReferenceException occurs. Looking at your code, here are some likely places (I'm making some assumptions since I don't know everything about your model):
Competitor = brief.BriefCompetitors.Where(i=>i.ID == b.BriefCompetitorID).Select(c=>c.Organisation.Name).First()
BriefCompetitors could be null. c.Organisation could be null.
IsPublished = b.Lookup_TonalityBatchStatus.ID == (int)TonalityBatchStatus.Published?"Yes":"No",
(and other similar lines) b.Lookup_TonalityBatchStatus might be null.
ImportantCount = b.TonalityItems.Count(i=> i.IsImportant),
(and other similar lines) b.TonalityItems might be null.
I believe this is because your count is returning null records. I could be wrong but the SQL that's being produced here is something like:
INNER JOIN TonalityItems i on i.Lookup_TonalityScoreTypes == x
Where x is the value of (int)TonalitySourceType.Favourable. Because this join has no matching results there is nothing to do a count on. You could try adding ?? 0 to the end of the query:
FavourableCount = b.TonalityItems.Count(i => i.Lookup_TonalityScoreTypes.ID ==(int)TonalitySourceType.Favourable) ?? 0,
I have a query as follows:
var query = from x in context.Employees
where (x.Salary > 0 && x.DeptId == 5) || x.DeptId == 2
order by x.Surname
select x;
The above is the original query and returns let's say 1000 employee entities.
I would now like to use the first query to deconstruct it and recreate a new query that would look like this:
var query = from x in context.Employees
where ((x.Salary > 0 && x.DeptId == 5) || x.DeptId == 2) && (x,i) i % 10 == 0
order by x.Surname
select x.Surname;
This query would return 100 surnames.
The syntax is probably incorrect, but what I need to do is attach an additional where clause and modify the select to a single field.
I've been looking into the ExpressionVisitor but I'm not entirely sure how to create a new query based on an existing query.
Any guidance would be appreciated. Thanks you.
In an expression visitor you would override the method call. Check if the method is Queryable.Where, and if so, the methods second parameter is a quoted expression of type lambda expression. Fish it out and you can screw with it.
static void Main()
{
IQueryable<int> queryable = new List<int>(Enumerable.Range(0, 10)).AsQueryable();
IQueryable<string> queryable2 = queryable
.Where(integer => integer % 2 == 0)
.OrderBy(x => x)
.Select(x => x.ToString());
var expression = Rewrite(queryable2.Expression);
}
private static Expression Rewrite(Expression expression)
{
var visitor = new AddToWhere();
return visitor.Visit(expression);
}
class AddToWhere : ExpressionVisitor
{
protected override Expression VisitMethodCall(MethodCallExpression node)
{
ParameterExpression parameter;
LambdaExpression lambdaExpression;
if (node.Method.DeclaringType != typeof(Queryable) ||
node.Method.Name != "Where" ||
(lambdaExpression = ((UnaryExpression)node.Arguments[1]).Operand as LambdaExpression).Parameters.Count != 1 ||
(parameter = lambdaExpression.Parameters[0]).Type != typeof(int))
{
return base.VisitMethodCall(node);
}
return Expression.Call(
node.Object,
node.Method,
this.Visit(node.Arguments[0]),
Expression.Quote(
Expression.Lambda(
lambdaExpression.Type,
Expression.AndAlso(
lambdaExpression.Body,
Expression.Equal(
Expression.Modulo(
parameter,
Expression.Constant(
4
)
),
Expression.Constant(
0
)
)
),
lambdaExpression.Parameters
)
)
);
}
}
}