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Entity Framework - Adhoc queries... Expand / Collapse
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Posted Monday, July 14, 2014 9:26 AM
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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.
Post #1592231
Posted Monday, July 14, 2014 10:10 AM


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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.




Jack Corbett

Applications Developer

Don't let the good be the enemy of the best. -- Paul Fleming

Check out these links on how to get faster and more accurate answers:
Forum Etiquette: How to post data/code on a forum to get the best help
Need an Answer? Actually, No ... You Need a Question
How to Post Performance Problems
Crosstabs and Pivots or How to turn rows into columns Part 1
Crosstabs and Pivots or How to turn rows into columns Part 2
Post #1592245
Posted Tuesday, July 15, 2014 6:52 AM
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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
Post #1592534
Posted Tuesday, July 15, 2014 7:35 AM


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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.



I also had the chance to tune EF systems. Same as you describe.
Because I didn't want to ask for many of the queries I realized that extending some of the non-clustered indexes have brought a lot of improvement for bunch of queries.
Anyway there is an "optimize for ad hoc workloads" option. It enables query plans to use less memory when cached.




Igor Micev,
SQL Server developer at Seavus
www.seavus.com
Post #1592559
Posted Tuesday, July 15, 2014 8:09 AM


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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.




Jack Corbett

Applications Developer

Don't let the good be the enemy of the best. -- Paul Fleming

Check out these links on how to get faster and more accurate answers:
Forum Etiquette: How to post data/code on a forum to get the best help
Need an Answer? Actually, No ... You Need a Question
How to Post Performance Problems
Crosstabs and Pivots or How to turn rows into columns Part 1
Crosstabs and Pivots or How to turn rows into columns Part 2
Post #1592586
Posted Tuesday, July 15, 2014 8:17 AM
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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.
Post #1592596
Posted Tuesday, July 15, 2014 7:31 PM
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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.
Post #1592876
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