To disable adaptive join for one query, add a USE HINT to it. This post also shows a Query Store hint for code you cannot edit and the database setting that switches the feature off for everything. Each switch is tested on a small demo database and checked in the plan.
Enable Adaptive Join in SQL Server: Why It Does Not Appear
To enable adaptive join in SQL Server, the compatibility level, the database setting and the query must all agree. This post builds a demo database and probes the plan under each condition. It also corrects older advice whose statements switch the feature off.
Adaptive Threshold Rows: How an Adaptive Join Chooses
Adaptive threshold rows is the row count at which an adaptive join switches from nested loops to a hash join. This post runs two queries on WideWorldImporters, reads each threshold from the cached plan, and shows which branch ran. The first query stays below its threshold and the second goes above it.
CHECKPOINT Covers One Database: Flush Data to Disk
CHECKPOINT covers one database, so to flush data to disk you run it in each database. A demo with two databases shows one flushed and one still dirty. A short script then flushes every database in one pass, and the post says when a flush is worth it.
Auditing Query Hints Left in Production Code
Start auditing query hints in modules and Query Store, rank the busiest statements, and test removal with measured plans and rollback.
Expensive Queries by query_hash: Total Cost, Not One Plan
Expensive queries by query_hash are ranked by total cost, not by single plans. A demo runs one lookup with 40 different literals and shows that the top single plan is a scan, while the grouped total, ranked by reads, points at the lookup. The query ranks by reads, CPU, time or runs.
SQL SERVER – Data and Index Compression – Real-World Conversation
Index Compression needs workload measurements of storage, I/O and CPU. A customer conversation prompted my earlier advice.