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Is optimize for ad hoc workloads enabled?
Like most things in SQL Server, there are a couple different ways you can enable (or disable) the option to Optimize for Ad hoc Workloads. This is an online server setting so this can be enabled without disrupting services and will apply to all database on the server.
What is ad hoc in SQL Server?
In SQL, an ad hoc query is a loosely typed command/query whose value depends upon some variable. Each time the command is executed, the result is different, depending on the value of the variable. An ad hoc query is short lived and is created at runtime.
What is an example of ad hoc hypothesis?
Ad hoc hypotheses are often characteristic of pseudoscientific subjects. For example, Albert Einstein’s addition of the cosmological constant to general relativity in order to allow a static universe was ad hoc. Although he later referred to it as his “greatest blunder”, it may correspond to theories of dark energy.
What is ad hoc activities?
An ad hoc activity or organization is done or formed only because a situation has made it necessary and is not planned in advance. The Council meets on an ad hoc basis to discuss problems. ad hoc committees to examine specific problems.
When to optimize for ad hoc workloads in SQL Server?
When setting the Optimize for Ad hoc Workloads option to 1, the SQL Server Database Engine will store a small compiled plan stub value in the plan cache when the query is compiled for the first time, rather than storing the full execution plan for that query.
When to re-use an adhoc query plan?
Once a query plan is in cache, it can be re-used. Queries that are parameterized can end up re-using a plan that’s already in cache, because the query text is exactly the same. When an adhoc query executes it will only re-use the plan in cache if it has the exact same text and input value (s).
How many adhoc plans are in the plan cache?
There are more than 10,000 adhoc plans in the plan cache. You might wonder why there isn’t a plan for all 100,000 adhoc queries that executed, and it has to do with how the plan cache works (it’s size based on available memory, when un-used plans are aged out, etc.).
How much memory is used for adhoc queries?
From this screenshot you can see that we have about 3GB total dedicated to the plan cache, and of that 1.7GB is for the plans of over 158,000 adhoc queries. Of that 1.7GB, approximately 500MB is used for 125,000 plans that execute ONE time only.