SQL Server 2016 Query store

1. SQL Server Query Store
Vitaliy Popovych

2. About me
• Vitaliy Popovych
• Database Developer at Intapp

3. Agenda
• Query Store
• How it works
• Configuration Options
• UI Management Studio
• Query Store Catalog Views
• Query Store Stored Procedures
• Best Practice with the Query Store
• Demo

4. Recompiling Execution Plans
• Changes made to a table or view referenced by the query (ALTER TABLE and
ALTER VIEW).
• Changes made to a single procedure, which would drop all plans for that
procedure from the cache (ALTER PROCEDURE).
• Changes to any indexes used by the execution plan.
• Updates on statistics used by the execution plan, generated either explicitly
from a statement, such as UPDATE STATISTICS, or generated automatically.
• Dropping an index used by the execution plan.
• An explicit call to sp_recompile.
• Large numbers of changes to keys (generated by INSERT or DELETE
statements from other users that modify a table referenced by the query).
• For tables with triggers, if the number of rows in
the inserted or deleted tables grows significantly.
• Executing a stored procedure using the WITH RECOMPILE option.

5. What is Query Store?

6. Query Store
Compile
Execute
Plan Store
Runtime Stats
Query Store
Schema

7. How to start

8. Common scenarios
• Quickly find and fix a plan performance regression by forcing the previous
query plan. Fix queries that have recently regressed in performance due to
execution plan changes.
• Determine the number of times a query was executed in a given time
window, assisting a DBA in troubleshooting performance resource
problems.
• Identify top n queries (by execution time, memory consumption, etc.) in
the past x hours.
• Audit the history of query plans for a given query.
• Analyze the resource (CPU, I/O, and Memory) usage patterns for a
particular database.

9. Enable Query Store
By Using Transact-SQL Statements
ALTER DATABASE [AdventureWorks2016CTP3]
SET QUERY_STORE = ON
(
CLEANUP_POLICY = (STALE_QUERY_THRESHOLD_DAYS = 31),
DATA_FLUSH_INTERVAL_SECONDS = 900,
INTERVAL_LENGTH_MINUTES = 5,
MAX_STORAGE_SIZE_MB = 1024,
QUERY_CAPTURE_MODE = ALL,
SIZE_BASED_CLEANUP_MODE = AUTO
)
GO
By Using the Query Store Page in Management Studio
- In the Database Properties dialog box, select the Query Store page.
- In the Enable box, select True.

10. Configuration Options
 OPERATION_MODE
 CLEANUP_POLICY
 DATA_FLUSH_INTERVAL_SECONDS
 MAX_STORAGE_SIZE_MB
 INTERVAL_LENGTH_MINUTES
 SIZE_BASED_CLEANUP_MODE
 MAX_PLANS_PER_QUERY

11. Configuration Options
MAX_STORAGE_SIZE_MB (Configures the maximum size of the
query store. If the data in the query store hits the
MAX_STORAGE_SIZE_MB limit, the query store automatically
changes the state from read-write to read-only and stops
collecting new data) default value = 100 MB
OPERATION_MODE (Can be READ_WRITE or READ_ONLY)
default value = READ_WRITE
CLEANUP_POLICY (Configure the
STALE_QUERY_THRESHOLD_DAYS argument to specify the
number of days to retain data in the query store)
default value = 367 days

12. Configuration Options
DATA_FLUSH_INTERVAL_SECONDS (Determines the frequency
at which data written to the query store is persisted to disk. To
optimize for performance, data collected by the query store is
asynchronously written to the disk. The frequency at which this
asynchronous transfer occurs is configured via
DATA_FLUSH_INTERVAL_SECONDS) default value = 900 sec
INTERVAL_LENGTH_MINUTES (Determines the time interval at
which runtime execution statistics data is aggregated into the
query store. To optimize for space usage, the runtime
execution statistics in the Runtime Stats Store are aggregated
over a fixed time window. This fixed time window is configured
via INTERVAL_LENGTH_MINUTES) default value = 60 min

13. Configuration Options
QUERY_CAPTURE_MODE (Designates if the Query Store
captures all queries, or relevant queries based on execution
count and resource consumption, or stops adding new queries
and just tracks current queries) default value = all
MAX_PLANS_PER_QUERY (An integer representing the
maximum number of plans maintained for each query)
default value = 200
SIZE_BASED_CLEANUP_MODE (Controls whether the cleanup
process will be automatically activated when total amount of
data gets close to maximum size)
default value = OFF

14. Information
Execution metric Statistic function
CPU time,
Duration,
Execution Count,
Logical Reads,
Logical writes,
Memory consumption,
Physical Reads
Average,
Maximum,
Minimum,
Standard Deviation,
Total

15. UI Management Studio
Regressed Queries (Pinpoint queries
for which execution metrics have recently
regressed i.e. changed to worse)
Overall Resource Consumption
(Analyze the total resource consumption
for the database for any of the execution
metrics)
Top Resource Consuming Queries
(Queries which have the biggest impact to
database resource consumption)
Tracked Queries (Track the execution of
the most important queries in real-time)

16. Regressed Queries
Pinpoint queries for which execution metrics have recently regressed (i.e. changed to
worse). Use this view to correlate observed performance problems in your application
with the actual queries that needs to be fixed or improved.

17. Overall Resource Consumption
Analyze the total resource consumption for the database for any of the execution
metrics. Use this view to identify resource patterns (daily vs. nightly workloads) and
optimize overall consumption for your database.

18. Top Resource Consuming Queries
Choose an execution metric of interest and identify queries that had the most extreme
values for a provided time interval. Use this view to focus your attention on the most
relevant queries which have the biggest impact to database resource consumption.

19. Tracked Queries
Track the execution of the most important queries in real-time. Typically, you use this
view when you have queries with forced plans and you want to make sure that query
performance is stable.

20. Query Store Catalog Views
• sys.database_query_store_options (Returns the Query Store
options for this database)
• sys.query_store_plan (Contains information about each execution plan
associated with a query)
• sys.query_store_query (Contains information about the query and
aggregated runtime execution statistics)
• sys.query_store_query_text (Contains the Transact-SQL text and
the SQL handle of the query)
• sys.query_store_runtime_stats (Contains information about the
runtime execution statistics information for the query)
• sys.query_store_runtime_stats_interval (Contains
information about the start and end)

21. Query Store Stored Procedures
• sp_query_store_flush_db (Flushes the in-memory portion of the
Query Store data to disk)
• sp_query_store_force_plan (Enables forcing a particular plan for a
particular query)
• sp_query_store_remove_plan (Removes a single plan from the
query store)
• sp_query_store_remove_query (Removes the query, as well as
all associated plans and runtime stats from the query store)
• sp_query_store_reset_exec_stats (Clears the runtime stats for
a specific query plan from the query store)
• sp_query_store_unforce_plan (Enables unforcing a particular
plan for a particular query)

22. Best Practice with the Query Store
• Use the Latest SQL Server Management Studio
• Keep Query Store Adjusted to your Workload
• Verify Query Store is Collecting Query Data
Continuously
• Set the Optimal Query Capture Mode
• Keep the Most Relevant Data in Query Store
• Avoid Using Non-Parameterized Queries
• Check the Status of Forced Plans Regularly

23. Demo

24. Resources
• SQLServer Blog
• MSDN
• A flight data recorder for your database (Borko Novakovic)
• The SQL Server Query Store (Benjamin Nevarez)

25. Question?

26. Thanks!
Vitaliy Popovych
E-mail: vitaliy.popovych@outlook.com