Calling .ToString() to a IQueryable will return the generated SQL query with the values of the variables not plugged in yet. So there are these p__linq__n with n=0, 1, 2... in the query itself.
eg: SELECT * FROM foo WHERE x = p__linq__0
Question: Is it possible to get the final query? with the values of these variables already plugged into the query?
eg: SELECT * FROM foo WHERE x = 6
EF parametrizes queries to avoid Sql injections attacks and to be able to cache and re-use the same query even if some values change. To see parameters you can use the logging feature introduced in EF6. See this blogpost series for more details.
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My application is using Entity Framework over a SQL Azure Database.
It has a feature that allows the the user to search for records based on a given phone number. The table being searched has many columns, including 3 columns for phone numbers: a BusinessPhone, a HomePhone and a CellPhone column. All three of these columns are indexed.
My EF DbContext is generating the following as part of the WHERE clause:
WHERE (10 = [Extent1].[Debtor_DebtorStatus]) AND
(((LOWER([Extent1].[BusinessPhone])) = (LOWER(N'012345678')))
OR ((LOWER([Extent1].[HomePhone])) = (LOWER(N'012345678')))
OR ((LOWER([Extent1].[CellPhone])) = (LOWER(N'012348678')))
)
The query is taking about 3 minutes to return a response (even when I run it in SQL Management Studio).
If I edit this SQL statement and remove the LOWER() function, then it executes in less than a second!!!
Is there some setting I can flick to make EntityFramework NOT use the LOWER() function in the generated SQL statement?
Of if that is not possible, is there a way I can intercept this SQL statement and remove the LOWER() functions in code before execution on the database?
I'm getting errors when I try and do something like this:
from s in db.SomeDbSet where IsValid(s) select s
It errors telling me that it can't process IsValid.
Basically what I'm trying to do is filter based on another dbSet inside the Where that is linked and does an any, but it won't let me.
I've tried a million different ways of doing a Expression but I can't find the right way and building my own Extension method like Where doesn't seem to work either.
Thanks!
Can you paste your IsValid function?
In this case it's EF job to take LINQ syntax and turn it into SQL syntax.
EF can't turn your function into SQL. it only supports a set number of functions that have a clear SQL equivalent commend.
you have two options:
1) Rewrite the function as a series of supported commends. This will be turned into a SQL sub-query, Meaning a single trip to the database, For example:
// will only return records that have at least one related entity marked as full.
query.Where(m => m.ReletedEntities.Any(re => re.IsFull == true));
2) Get all the data from the database and then using Linq and your function work with the data. this will be done in memory using your actual function that will be called once for every item in the collection. You will also have to load the related entity collection. or it will still be an "entity framework translated to SQL query", And will fail if you use your function.
I'm using EF 6 beta1. I have a simple stored proc that returns two result sets:
ALTER PROCEDURE GetItemsByParentId
#parentID int
SELECT * FROM Table1 WHERE ParentID = #parentID
SELECT * FROM Table2 WHERE ParentID = #parentID
I want to call that stored proc using my ObjectContext. I'm using database first and I have an edmx, but I don't want to import the stored proc as a function if I don't have to.
I created two simple classes Table1DTO and Table2DTO to store the results of the stored proc. For the first result set I call this:
var result1 = ExecuteStoreQueryAsync< Table1DTO >("EXEC GetItemsByParentId #parentID", new SqlParameter("parentID", parentID));
List table1DTOList = result1.ToList();
That works fine. Then for the second result set I'm trying this:
var result2 = result.GetNextResult< Table2DTO >();
List improvementDetailInfos = result2.ToList();
The problem is result2 is coming back as null. What am I missing?
This may sound like splitting hairs, but Entity Framework supports multiple result sets. The problem is that the Entity Framework Tooling does not. This has been an issue since EF 4.1/4.2. So you have three options (that I can think of):
split up your calls to only use single result sets
use an alternate technology (dapper?) for the few critical stored procedures that require multiple result sets
manually edit the EDMX to create a multi-result set mapping for GetItemsByParentId
To be honest I've wrestled with this in a number of scenarios and none of the options are great. If you're something of a masochist, I wrote up an example and answered a question on how to edit the EDMX for multiple result sets.
I have a generic code that is used to retrieve DDL information from a Firebird database (FB2.1). It generates SQL code like
SELECT * FROM MyTable where 'c' <> 'c'
I cannot change this code. Actually, if that matters, it is inside Report Builder 10.
The fact is that some tables from my database are becoming a litle too populated (>1M records) and that query is starting to take too long to execute.
If I try to execute
SELECT * FROM MyTable where SomeIndexedField = SomeImpossibleValue
it will obviously use that index and run very quickly.
Well, it wouldn´t be that hard to the database find out that that is an impossible matcher and make some sort of optimization and avoid testing it against each row.
Is there any way to make my firebird database to optimize that search?
As the filter condition is a negative proposition (and also doesn't refer a column to search, but only a value to compare to another value), Firebird need to do a full table scan (without use any index) to confirm that aren't any record that meet your criteria.
If you can't change you need to wait for the upcoming 3.0 version, that will implement the Boolean data type, and therefore should start to evaluate "constant" fake comparisons in advance (maybe the client library will do this evaluation before send the statement to the server?).
Let's say I have a SQL 2005 database with a table called Restaurants. The Restaurants table has the following columns:
RestaurantId
Name
Latitude
Longitude
I want to let users search for restaurants by name and/or address. How do I write the LINQ query to support this? I need to be able to support the possibility that the user doesn't enter in a name or address, just the name, just the address, or both name and address.
My initial idea was to write a stored procedure to calculate the distance between two lat/long pairs and a table value function for calling FREETEXTTABLE and using some conditional Join calls on my query. However, it appears that Entity Framework 4 doesn't support table value functions.
You certainly can write a proc which returns entity types. Indeed, in EF 1 that was the only option for procs. The proc returns a set of values, not a table, but I can't see that you actually need this.
You can also do free-form T-SQL in EF 4 using Context.ExecuteStoreQuery.
You cannot write any LINQ that supports geospatial queries at this point of time - be it EF or LinqToSql. This is because there is no LINQ syntax which can handle the special ST<whatever> spatial syntax that exists in SQL Server 2008. (eg. STIntersects(..))
You will need to write a Stored Procedure which you can then get access to via EF.
If you wish to return a Sql GEOGRAPHY field in a result, you will need to return a VARBINARY(MAX) i think as the equivalent field type for the C# code.
Hope This Helps.