procedure cache Archives - Grant Fritchey

22Oct 2018 by Grant Fritchey 6 Comments

Why Did a Plan Get Removed From Cache?

SQL Server, SQL Server 2016, SQL Server 2017, T-SQL

I was recently asked if we could tell why a plan was removed from cache. If you read this blog, you know what I'm going to say next. I checked the extended events and there are actually two different events that will tell us information about a plan removed from cache; sp_cache_remove and query_cache_removal_statistics. Let's talk about how these work. Removed From Cache Just so we can see ALL the activity, I'm creating an Extended Events session that captures a little more than just the two events: CREATE EVENT SESSION PlanCacheRemoval ON SERVER ADD EVENT sqlserver.query_cache_removal_statistics (WHERE (sqlserver.database_name = N'AdventureWorks2017')), ADD EVENT sqlserver.rpc_completed (WHERE (sqlserver.database_name = N'AdventureWorks2017')), ADD EVENT sqlserver.rpc_starting (WHERE (sqlserver.database_name = N'AdventureWorks2017')), ADD EVENT sqlserver.sp_cache_hit (WHERE (sqlserver.database_name = N'AdventureWorks2017')), ADD EVENT sqlserver.sp_cache_insert (WHERE (sqlserver.database_name = N'AdventureWorks2017')), ADD EVENT…

10Sep 2018 by Grant Fritchey 1 Comment

Estimated Plans and Forced Plans from Query Store

SQL Server 2016, SQL Server 2017, T-SQL

While all plans are estimated plans, there is still a difference between capturing an estimated plan and looking at a plan from the cache or from query store. Or is there? A question came up during a recent presentation; what happens to capturing an estimated plan when you're forcing plans? Let's find out. The answer is interesting. Estimated Plans Here's my stored procedure that I'll be using with AdventureWorks2017: CREATE OR ALTER PROC dbo.ProductTransactionHistoryByReference (@ReferenceOrderID INT) AS BEGIN SELECT p.Name, p.ProductNumber, th.ReferenceOrderID FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON th.ProductID = p.ProductID WHERE th.ReferenceOrderID = @ReferenceOrderID; END; For reasons I'll explain in a bit, I'm going to free the procedure cache: ALTER DATABASE SCOPED CONFIGURATION CLEAR PROCEDURE_CACHE; Then, if I capture an estimated plan for two different values:…

11Mar 2009 by Grant Fritchey 1 Comment

A Fix for nHibernate’s Parameter Problem

nHibernate, Visual Studio

I had previously outlined a problem with nHibernate code that, in my opinion, was going to cause a lot of problems on production systems especially with memory and the procedure cache. However, it does appear that there is a possible solution. That doesn't eliminate my concerns over nHibernate, but it sure does help.

Tag: procedure cache