Entity Framework - Adhoc queries...

  • Jack Corbett (7/15/2014)


    Chord77 (7/15/2014)


    I am interested in this, are there any good resources for learning more about T4 templates? (A quick search shows lots of questions asking about T4 templates)

    Thanks

    There isn't a lot out there for T4 tempates with SSDT because it is so new. The only blog post I've found is this, http://dataidol.com/davebally/2014/03/29/t4-support-in-ssdt/ and it is very basic. I'm keeping my eye out for the video to be posted of this SQLBits Session scheduled to be presented this Saturday, http://www.sqlbits.com/Sessions/Event12/T4_Templating_within_SSDT_using_SQL_Server_2014, as I'm hoping this helps clear up some questions I have as to how to best incorporate T4 templates in my projects.

    Thanks I'll keep my eye out for it as well. This could be very useful.

  • Just wanted to point out I was looking at the result of a LINQ query last week that was causing a deadlock.

    Update [Table] -- Ok

    Set [Some Field] = @P1 -- Ok

    Where

    [Identity Column] = @P2 -- Great!

    And [Other Column 1] = @P3

    And [Other Column 2] = @P4

    -- Stop!

    ...

    And [Other Column 50] = @P52

    -- No LINQ! Please, Stop!

    ...

    And [Other Column 150] = @P152

    -- What the hell just happened

    Unfortunately the programmer couldn't correlate the SQL that was generated to the source of the LINQ code that caused it... so it's still out there. Somewhere. Causing harm.

  • Chord77 (7/15/2014)


    Jack Corbett (7/14/2014)


    mortonsoft (7/14/2014)


    GilaMonster (7/9/2014)


    Jack Corbett (7/9/2014)


    1. Scaling - ORM tools still aren't very good at complex SQL (multiple joins, outer joins, etc...) so you need to evaluate every query that EF is sending and be ready to replace "bad" queries with stored procedures.

    2. Tight coupling - if you really want to take full advantage of EF or any other ORM toll it means that you are tightly coupling the data access layer to your database. That means you are stuck with a specific database design until you can change the application as well. Whereas a design that provides an "API" to the database via views/functions/procedures allows you to change the underlying schema of the database as long as your API presents the same shape data to the application.

    3. Tuning - if there is a poorly performing query there is little you can do to tune it. The SQL is generated so, AFAIK, you can't provide hints (OPTION (RECOMPILE) to help with "bad" parameter sniffing) or re-shape it to get a different plan.

    Agreed on all points. I'm busy tuning a system which uses EF and thousand line long SQL statements are the norm, queries which fetch every column from the table, queries which fetch every row from multiple tables in a set of UNIONS, etc. Half the queries all I can do is send them to the dev and ask what the point is and whether they can be moved to stored procs.

    EF is fine for simple queries. Sure beats writing a few hundred CRUD procedures.

    Thanks, Jack and GM -- this was very, very helpful.

    Just a note about having to write CRUD procedures. With the March release of SSDT, you can now use T4 templates to generate all your basic CRUD procedures, so once you have written a template for that the creation of CRUD procs takes seconds.

    I am interested in this, are there any good resources for learning more about T4 templates? (A quick search shows lots of questions asking about T4 templates)

    Thanks

    Download the free ebook, T4 Succinctly by Nick Harrison. You can download after providing some basic information. You will get a phone call from Syncfusion after downloading, but it's nothing high pressure and they won't bother you again.



    Del Lee

Viewing 3 posts - 16 through 18 (of 18 total)

You must be logged in to reply to this topic. Login to reply