#sql server option recompile

[greyshyper]

Sql server option recompile

#SQL SERVER OPTION RECOMPILE SERIAL#

#SQL SERVER OPTION RECOMPILE CODE#

Use of a temporary table within an SP also causes recompilation of that statement. Since we have auto-update statistics off, we have less recompilation of SP's to begin with. This plan reuse system works as long as objects are qualified with it owner and DatabaseName (for e.g. If all four tables have changed by about 20% since last statistics update, then the entire SP is recompiled. If say, you are accessing four tables in that SP and roughly 20% of the data for one table has been found to have changed since last statistics update, then that statement is recompiled. Recompilation happens only when about 20% of the data in the tables being called from within the SP is found to have changed since the last time statistics was updated for those tables and its indexes. So usage of different input parameters doesn't cause a recompilation. New input parameters in the current execution replace the previous input parameters from a previous execution plan in the execution context handle which is part of the overall execution plan.

#SQL SERVER OPTION RECOMPILE SERIAL#

The new plan is discarded imeediately after execution of the statement.Īssuming both of these options are not being used, an execution of an SP prompts a search for pre-existing plans (one serial plan and one parallel plan) in memory (plan cache). Any pre- existing plan even if it is exactly the same as the new plan, is not used. When used with a TSQL statement whether inside an SP or adhoc, Option 2 above creates a new execution plan for that particular statement. There is no caching of the execution plan for future reuse. Once the SP is executed, the plan is discarded immediately. Any existing plan is never reused even if the new plan is exactly the same as any pre-existing plan for that SP. It can not be used at a individual statement level.

#SQL SERVER OPTION RECOMPILE CODE#

When used in the code of a particular Stored procedure, Option 1compiles that SP everytime it is executed by any user. We should use RECOMPILE option only when the cost of generating a new execution plan is much less then the performance improvement which we got by using RECOMPILE option.WITH RECOMPILE This is because of the WITH RECOMPILE option, here each execution of stored procedure generates a new execution plan. Here you see the better execution plan and great improvement in Statistics IO. Now execute this stored procedure as: set statistics IO on Now again creating that stored procedure with RECOMPILE option. Here when we execute stored procedure again it uses the same execution plan with clustered index which is stored in procedure cache, while we know that if it uses non clustered index to retrieve the data here then performance will be fast. Now executing the same procedure with different parameter value: set statistics IO on The output of this execution generates below mention statistics and Execution plan: Select address,name from xtdetails where execute this stored procedure as: set statistics IO on Now create stored procedure as shown below: create procedure as varchar(50)) Set into xtdetails table xtdetails contains 10000 rows, where only 10 rows having name = asheesh and address=Moradabad. Now, I am inserting the data into this table: declare as int Ĭreate clustered index IX_xtdetails_id on xtdetails(id)Ĭreate Nonclustered index IX_xtdetails_address on xtdetails(address) In this case if we reuse the same plan for different values of parameters then performance may degrade.įor Example, create a table xtdetails and create indexes on them and insert some data as shown below: CREATE TABLE. But sometimes plans generation depends on parameter values of stored procedures. If plan found in cache then it reuse that plan that means we save our CPU cycles to generate a new plan. If we again execute the same procedure then before creating a new execution plan sql server search that plan in procedure cache. When we execute stored procedure then sql server create an execution plan for that procedure and stored that plan in procedure cache. Here i am focusing on why we use WITH RECOMPILE option. Some time, we also use WITH RECOMPILE option in stored procedures. We use stored procedures in sql server to get the benefit of reusability. Today here, I am explaining the Use of Recompile Clause in SQL Server Stored Procedures.

[mainsengineer]

Sql server option recompile

SQL SERVER OPTION RECOMPILE SOFTWARE

SQL SERVER OPTION RECOMPILE CODE

SQL SERVER OPTION RECOMPILE FREE

I’m also available for consulting if you just don’t have time for that and need to solve performance problems quickly. I’m offering a 75% discount on to my blog readers if you click from here. If this is the kind of SQL Server stuff you love learning about, you’ll love my training. I’m not mad.Īnd yeah, there’s advances in SQL Server 20 that start to address some issues here, but they’re still imperfect. Using a plan guide doesn’t interfere with that precious vendor IP that makes SQL Server unresponsive every 15 minutes.

Plan Guides: An often overlooked detail of plan guides is that you can attach hints to them, including recompile.

You can single out troublesome queries to remove specific plans.

DBCC FREEPROCCACHE: No, not the whole cache.

Sure, you might be able to sneak a recompile hint somewhere in the mix even if it’d make the vendor upset.

SQL SERVER OPTION RECOMPILE SOFTWARE

For third party vendors who have somehow developed software that uses SQL Server for decades without running into a single best practice even by accident, it’s often harder to get those changes through. And yeah, sometimes there’s a good tuning option for these, like changing or adding an index, moving parts of the query around, sticking part of the query in a temp table, etc.īut all that assumes that those options are immediately available. Those are very real problems that I see on client systems pretty frequently.

SQL SERVER OPTION RECOMPILE CODE

CPU spikes for high-frequency execution queries: Maybe time for caching some stuff, or getting away from the kind of code that executes like this (scalar functions, cursors, etc.)īut for everything in the middle: a little RECOMPILE probably won’t hurt that bad.Sucks less if you have a monitoring tool or Query Store. No plan history in the cache (only the most recent plan): Sucks if you’re looking at the plan cache.Long compile times: Admittedly pretty rare, and plan guides or forced plans are likely a better option.Not necessarily caused by recompile, but by not re-using plans. Here are some problems you can hit with recompile. But as I list them out, I’m kinda shrugging. Obviously, you can run into problems if you (“you” includes Entity Framework, AKA the Database Demolisher) author the kind of queries that take a very long time to compile. And if you put it up against the performance problems that you can hit with parameter sniffing, I’d have a hard time telling someone strapped for time and knowledge that it’s the worst idea for them. You can do it in SSMS as well, but Plan Explorer is much nicer.It’s been a while since SQL Server has had a real RECOMPILE problem. Look at details of each operator in the plan and you should see what is going on.

SQL SERVER OPTION RECOMPILE FREE

I would recommend to look at both actual execution plans in the free SQL Sentry Plan Explorer tool. Without OPTION(RECOMPILE) optimiser has to generate a plan that is valid (produces correct results) for any possible value of the parameter.Īs you have observed, this may lead to different plans. If there are a lot of values in the table that are equal to 1, it would choose a scan. If there is only one value in the table that is equal to 1, most likely it will choose a seek. Also, optimiser knows statistics of the table and usually can make a better decision. It does not have to be valid for any other value of the parameter. The generated plan has to be valid for this specific value of the parameter. With OPTION(RECOMPILE) optimiser knows the value of the variable and essentially generates the plan, as if you wrote: SELECT * And simple (7 rows) and actual statistics. With OPTION (RECOMPILE) it uses the key lookup for the D table, without it uses scan for D table. INSERT INTO D (idH, detail) VALUES 'nonononono') INSERT INTO H (header) VALUES ('nonononono') The script is: Create two tables: CREATE TABLE H (id INT PRIMARY KEY CLUSTERED IDENTITY(1,1), header CHAR(100))ĬREATE TABLE D (id INT PRIMARY KEY CLUSTERED IDENTITY(1,1), idH INT, detail CHAR(100)) I am lost why execution plan is different if I run query with option recompile to compare to same query (with clean proc cache) without option recompile.