Intelligent Query Processing (IQP) - SQL Server 2022

Intelligent Query Processing (IQP) is a set of features introduced in SQL Server 2017 to optimize and improve the performance of queries in SQL databases. These features use machine learning algorithms to adapt and optimize query execution plans based on data statistics, query patterns, and other factors. SQL Server 2022 builds upon these features and introduces several enhancements to further improve query performance.

Here are some of the enhancements to Intelligent Query Processing in SQL Server 2022, along with examples:

Scalar UDF Inlining: User-Defined Functions (UDFs) can be used to encapsulate complex logic and make queries more readable. However, they can also negatively impact query performance. With Scalar UDF Inlining, SQL Server 2022 can automatically inline scalar UDFs into queries, reducing the overhead of calling the UDF multiple times.

For example, consider the following query with a scalar UDF:

SELECT dbo.CalculatePrice(OrderDate, OrderQty, UnitPrice) FROM Sales.OrderDetails

With Scalar UDF Inlining, SQL Server 2022 can inline the UDF into the query:

SELECT (OrderQty * UnitPrice * CASE
    WHEN OrderDate > '2021-01-01' THEN 1.2
    ELSE 1
END) FROM Sales.OrderDetails

Table Variable Deferred Compilation: Table variables are temporary objects used to store data within a query. They are often used as an alternative to temporary tables. With Deferred Compilation, SQL Server 2022 can compile and optimize queries that use table variables at runtime, reducing the overhead of recompiling the query multiple times.

For example, consider the following query that uses a table variable:

DECLARE @TempTable TABLE (ID INT, Name NVARCHAR(50))

INSERT INTO @TempTable
SELECT ID, Name FROM dbo.Customers WHERE State = 'CA'

SELECT * FROM @TempTable

With Deferred Compilation, SQL Server 2022 can compile and optimize the query at runtime, reducing the overhead of recompiling the query multiple times.

Batch Mode Adaptive Joins: Batch Mode Adaptive Joins are a new feature in SQL Server 2022 that automatically adjusts the join type based on data statistics and query patterns. This can improve query performance by reducing the need for expensive sort operations.
For example, consider the following query:

SELECT * FROM Sales.Orders o JOIN Sales.OrderDetails d ON o.OrderID = d.OrderID

With Batch Mode Adaptive Joins, SQL Server 2022 can automatically adjust the join type based on data statistics and query patterns. This can improve query performance by reducing the need for expensive sort operations.

Approximate Query Processing: Approximate Query Processing (AQP) is a feature in SQL Server 2022 that provides an approximate answer to a query, without the need for a full scan of the data. This can be useful for queries that require fast, approximate results, such as real-time dashboards or ad-hoc queries.
For example, consider the following query that calculates the average order value:

SELECT AVG(OrderValue) FROM Sales.Orders

With Approximate Query Processing, SQL Server 2022 can provide an approximate answer to the query, without the need for a full scan of the data. This can be useful for queries that require fast, approximate results.

Overall, the enhancements to Intelligent Query Processing in SQL Server 2022 are designed to improve query performance, reduce query overhead, and provide more efficient query execution plans. These features can be especially useful for large, complex SQL Server workloads, where query performance can have a significant impact on overall application performance.



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