shopping around for query optimizations? try the query store!

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SQL Server 2016 The Query StoreAuthor: Sean WerickCompany: Pragmatic Works


Who is Pragmatic Works? o 100% Microsoft SQL Server Focused o Team of Microsoft MVPs, Authors, Presenterso Concentrated on Optimizing your Data Lifecycle

What is Pragmatic Works? o Software Solutions o Training Offeringso Professional Services

Why Pragmatic Works? o Microsoft Gold Partner – Data Platform & Business Intelligence o Microsoft’s only “National Solution Provider” for Business Intelligence o Microsoft Analytics Platform System Implementation Partner of the Yearo INC Magazine’s Fastest 5000 Growing Companies o Leader in offerings centered around Microsoft’s emerging technologies

About Pragmatic Works


• Principal Consultant• Community Speaker• Blogs: www.seanwerick.com• Email: [email protected]

About Sean

http://www.seanwerick.com/

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What is the Query Store?A SQL Server 2016 (and SQL DB) Feature that can be Enabled

• Provides insight on query plan choice and performance

• Simplifies performance troubleshooting by quickly finding performance differences caused by query plan changes

• Automatically captures a history of queries, plans, and runtime statistics, and retains these for review

• Separates data by time windows to better illustrate database usage patterns and understand when query plan changes happened on the server


Why Use the Query Store?Query Performance Insight Helps Satisfy 2 Main Goals

Performance Cost


WHAT IS THE REAL COST?

Why Use the Query Store?

All about the DTUs (PaaS)

A Database Transaction Unit (DTU) is a blended measure of the resources allocated at each performance level.

• Processor - % Processor Time• Logical Disk - Disk Reads/sec• Logical Disk - Disk Writes/sec• Database - Log Bytes Flushed/sec

• Review the list of top resource-consuming queries

• Select an individual query to view its details

• Click Settings to customize how data is displayed or to show a different time period

• Open Index Advisor* (PaaS) and check if any recommendations are available

Performance Cost

* Index Advisor - https://azure.microsoft.com/en-us/documentation/articles/sql-database-index-advisor/


How the Query Store “Works”


Does It Work with In-Memory OLTP?

• SQL Server Query Store allows you to monitor the performance of natively compiled code for workloads running in-memory OLTP

• Compile and runtime statistics are collected and exposed the same way as for disk-based workloads

• When you migrate to in-memory OLTP you can continue using Query Store views in SQL Server Management Studio as well as custom scripts you have developed for disk-based workloads before migration

• This saves your investment in learning Query Store technology and makes it generally usable for troubleshooting all type of workloads


How to Use the Query StoreIn Just 3 Easy Steps, You TOO can be a DBA!!

Okay, okay. This may take a bit more effort and knowledge.


There are 2 Ways to Enable Query Store

By Using the Query Store Page in SSMS

Setting up the Query Store

In Object Explorer, right-click a database, and then click Properties


By Using the Query Store Page in SSMS


In the Database Properties dialog box, select the Query Store pageSelect related attributes• General

o Operation Mode (Read or Read/Write)• Monitoring

o Data Flush Interval (Manual Entry in Minutes)o Statistics Collection (5 mins, 10 mins, 15 mins, 30 mins, 1 hr,

1 day)• Max Size

o Query Store Capture Mode (All or Auto)o Size Based Cleanup Mode (Off or Auto)o Stale Query Threshold (Manual Entry in Days)


By Using T-SQL Statements

• Use the ALTER DATABASE statement ALTER DATABASE AdventureWorks2012 SET QUERY_STORE = ON;Ability to



GUI Option T-SQL OptionOperation Mode (Requested) OPERATION_MODE

Data Flush Interval (Minutes) DATA_FLUSH_INTERVAL_SECONDS

Statistics Collection Interval INTERVAL_LENGTH_MINUTES

Max Size (MB) MAX_STORAGE_SIZE_MB

Query Store Capture Mode QUERY_CAPTURE_MODE

Size Based Cleanup Mode SIZE_BASED_CLEANUP_MODE

Stale Query Threshold (Days) CLEANUP_POLICY (STALE_QUERY_THRESHOLD_DAYS)

MAX_PLANS_PER_QUERY

Query Store Options with T-SQLALTER DATABASE [db_name]SET QUERY_STORE ( [Query Store options] );

-- ExampleALTER DATABASE AdventureWorksSET QUERY_STORE ( MAX_STORAGE_SIZE_MB = 250 );


sys.query_store_plansys.query_store_runtime_stats

sys.query_context_settings

sys.query_store_runtime_stats_interval

sys.query_store_query

sys.query_store_query_text

plan_id

runtime_stats_interval_id

query_id

context_settings_id

query_text_id

DATA MODEL

sys.database_query_store_options

What Information Does It Provide?


What Information Does It Provide?

*Additional Detail - https://msdn.microsoft.com/en-us/library/dn818146.aspx

Query Store View Description

sys.database_query_store_options Query Store options for this database

sys.query_context_settings Semantics affecting context settings associated with a query (The same query text compiled under different settings may produce different results [depending on the underlying data])

sys.query_store_plan Each execution plan associated with a query

sys.query_store_query Information about the query and its associated overall aggregated runtime execution statistics

sys.query_store_query_text Transact-SQL text and the SQL handle of the query

sys.query_store_runtime_stats Information about runtime execution statistics information for the query

sys.query_store_runtime_stats_interval Information about the start and end time of each interval over which runtime execution statistics information for a query has been collected


Query Store Best Practices Information and performance are generally a give and take, but there ARE some

best practices

Every single setting in the Query Store has associated costs and benefits

• Treat Query Store performance tuning like an agile project with Sprints

o Sprint 1 – Keep Operation Mode in READ/WRITE mode for information collection

This reduces write time, and subsequent overall database performance, for data collection as no reporting is occurring

o Sprint 2 – Change Operation Mode to READ mode for analysis and actual performance tuning

This it increases report performance because no writes are occurring. This also results in no “dirty reads” because of the asynchronous writes


Query Store Best Practices

• Flush the data at specific business case intervals. For example, if performance of the DB seems to be poor around end of the month due financial reporting, consider using the Agile methodology to complete one iteration, then flush the data before the next iteration.

• Keep the Max Size small enough to keep the reporting relatively snappy, however, keep enough data to capture all of the business needs

• Keep an accurate Cleanup Policy as the business and reporting solution evolves

• Collect statistics as frequently as possible to see exactly which execution plans are being executed. If the statistics are not updated for some time, you may be looking at an old execution plan because the statistics have changed

Information and performance are generally a give and take, and it ultimately relies on each and every business and its processes


Query Store ReportingAzure SQL DB• Cloud offering (PaaS)

• Learn and adapt dynamically with your app

• Scale performance on the fly, without app downtime

• Build multitenant apps with customer isolation and efficiency

• Work within your preferred development environments

• Help protect and secure your app data


Query Store ReportingThe top queries view opens and the top CPU consuming queries are listed

• The top line shows overall DTU% for the database, while the bars show CPU% consumed by the selected queries during the selected interval

• The bottom grid represents aggregated information for the visible queries

o Average CPU per query during observable interval

o Total duration per query

o Total number of executions for a particular query


Query Store ReportingViewing Individual Query Details

Click any query in the list of top queries.

The details view opens and the queries CPU consumption is broken down over time.

Click around the chart for details.The top line is overall DTU%, and the bars are CPU% consumed by the selected query.

Review the data to see detailed metrics including duration, number of executions, and resource utilization percentage for each interval the query was running.


Query Store On Premise ReportingOn Premise Solution?


Query Store DashboardsSSMS


Custom Views and SQLHOW?

sys.query_store_plansys.query_store_runtime_stats

sys.query_context_settings

sys.query_store_runtime_stats_interval

sys.query_store_query

sys.query_store_query_text

plan_id

runtime_stats_interval_id

query_id

context_settings_id

query_text_id

sys.database_query_store_options


Query Store Admin with T-SQLStored Procedure Description

sp_query_store_flush_db Flushes the in-memory portion of the Query Store data to disk

sp_query_store_reset_exec_stats Clears the runtime stats for a specific query plan from the query store

sp_query_store_force_plan Enables forcing a particular plan for a particular query.

When a plan is forced for a particular query, every time SQL Server encounters the query, it tries to force the plan in the optimizer. If plan forcing fails, a XEvent is fired and the optimizer is instructed to optimize in the normal way.

sp_query_store_unforce_plan Enables unforcing 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


Forcing Execution Plans

OLD WAY1. Run SET SHOWPLAN_XML ON to return the XML

Execution Plan, or alternatively, grab the XML Plan from the sys.dm_exec_text_query_plan DMF)

2. Create the Plan Guide using the sp_create_plan_guide Stored Procedure


Forcing Execution Plans

NEW WAY1. Click the “Force Plan” button inside one of the

Query Store reports

2. Use the sp_query_store_force_plan SP.EXEC sp_query_store_force_plan 136, 146;


Error StateRemember to verify intermittently that the Query Store is still collecting data

SELECT actual_state_desc, desired_state_desc, current_storage_size_mb, max_storage_size_mb, readonly_reason, interval_length_minutes, stale_query_threshold_days, size_based_cleanup_mode_desc, query_capture_mode_desc

FROM sys.database_query_store_options;

If there is a difference between the actual_state_desc and desired_state_desc, this indicates that a change of operations mode occurred automatically.

The most common change is for the Query Store to silently switch to read-only mode. In extremely rarely circumstances, Query Store can end up in the ERROR state because of internal errors.

When the actual state is read-only, use the readonly_reason column to determine the root cause. Typically, the Query Store transitioned to read-only mode because the size quota was exceeded. In that case the readonly_reason is set to 65536.


Error StateHow to Fix

Reactive

Increase the maximum storage size by using the MAX_STORAGE_SIZE_MB option of ALTER DATABASE

Clean up Query Store data ALTER DATABASE [QueryStoreDB] SET QUERY_STORE CLEAR;

Change Operation Mode back to READ/WRITE ALTER DATABASE [QueryStoreDB] SET QUERY_STORE (OPERATION_MODE = READ_WRITE);

Proactive

Apply best practices, specifically related to Query Store size

Make sure that most recent data is retained, configure time-based policy to remove stale information regularly

Consider setting Query Capture Mode to Auto as it filters out queries that are usually less relevant for your workload


Questions and Answers

shopping around for query optimizations? try the query store!

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