Compiling a query results in client side evaluation

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#13,976 12 comments 1 reaction 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
csharp
Domain
database

Research direction

Start with the provided C# reproduction using EF.CompileQuery and the SQL Server provider, then inspect the generated SQL for the compiled and uncompiled queries. Done means the compiled query produces the expected WHERE clause and no longer evaluates this predicate on the client.

Written by the indexing model from the issue text.

Description

area-query customer-reported

A have a query that references values in a class. This works as expected when the query is not compiled. When the query is compiled it executes on the client. This can be seen by the lack of a where clause in the generated SQL. This works correctly in EF6.

Steps to reproduce

Run the provided code.

class MyKey
{
    public string CompanyID;
}

private static void Repro(IceContext db)
{
    var key = new MyKey() { CompanyID = "MyValue" };

    // Not compiled it correctly evaluates on the server.
    var result1 = (from row in db.SysUserComp
                    where row.Company == key.CompanyID
                    select row).FirstOrDefault();

    // Compiled it evaluates on the client.
    Expression<Func<IceContext, MyKey, SysUserComp>> expression =
        (ctx, key_ex) =>
        (from row in ctx.SysUserComp
            where row.Company == key_ex.CompanyID
            select row).FirstOrDefault();
    var compiledQuery = EF.CompileQuery(expression);

    var result2 = compiledQuery(db, key);
}
Further technical details

EF Core version: 2.1.1
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10
IDE: Visual Studio 2017 15.8.9

Dominant language
C#
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