What is the oldest compatibility level supported by SQL Server 2022? It goes back to SQL Server 2005, and here is why that backward compatibility matters.
SQL SERVER – Impact of Changing Database Compatibility Level on Cache
Changing the database compatibility level can clear plans from cache. Here is what happens to the query cache and why it matters.
SQL Server 2022 – Cardinality Estimation (CE) Feedback for Performance
SQL Server 2022introduces an enhanced Cardinality Estimation (CE) feedback feature as part of the intelligent query processing family.
SQL Server 2022 – Degree of Parallelism (DOP) Feedback for Optimize Query Performance
SQL Server 2022 introduces a powerful new feature called Degree of Parallelism (DOP) feedback as part of the Intelligent Query Processing (IQP).
SQL SERVER – Availability Groups Can Propagate Database Compatibility Level
Propagation of Compatibility Level needs verification on the actual availability-group topology. I compare each replica through its own connection.
Performance Regression After a SQL Server Upgrade: First Aid
A performance regression after an upgrade hurts most when users are waiting. This post shows a first-aid switch that brings back the old row estimates without lowering the compatibility level, and proves with a demo what changes and what stays. It also covers the undo, the per-query options and the steps that find the real cause.
FORCE_DEFAULT_CARDINALITY_ESTIMATION: A Simple Explanation
FORCE_DEFAULT_CARDINALITY_ESTIMATION is a query hint that gives one query the default cardinality estimator, even when the database is set to the legacy one. This post builds a demo table, compares the row estimates of both models with the real count and shows how to prove which model a plan used. It also names the opposite hint and the permission difference.