SQL Server 2016 Query Store

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Darlene Gibson
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SQL Server 2016 Query Store Sergio Govoni Twitter:

1 SQL Server 2016 Query Store Sergio Govoni Blog:

2 Sergio Govoni SQL Server MVP ugiss.org manning.com/delaney

3 Agenda Query Store in SQL Server 2016 (RC2) Query plan choice change can cause performance issues What does the Query Store do for you?

4 Plan changes can cause performance issues Web site is down Temporary perf. issues SQL Server upgrade Database is not working How to fix it ASAP? Impossible to predict the root cause Performance regression caused by the new version

5 Why do plan changes happen? Query Optimizer generates and evaluates many plans for the same query Data changes every hour, so the QO might select a different plan Generally, boundary plans have the same performance

6 Fixing query plan regression is hard Problems you face for slow running queries Time of the day and compiled parameters Has the Data Collector been activated? Plan cache may not be suitable for troubleshooting You have to find out why it is show When you have the issue on you hands Can you modify the query text? Do you know the SP to create the Plan Guide?

7 What does the Query Store do for you? It stores all the plan choices and related performance metrics for each query It identifies queries that have become slower recently It allows DBA to force an execution plan easily It makes sure your changes work across server restart, upgrades, failover and query recompiles

8 How the Query Store captures data

9 How the Query Store exposes data Each DMV joined In- Memory and On-Disk data Query Store reports When memory pressure occurs, some data In- Memory will be flushed to the disk In-Memory Data On-Disk Data sys.query_store_runtime_stats

10 How the Query Store interprets the query text Query text starts from the first character of the first token (of the statement) and it ends at the last character of the last token Comments and spaces, before or after, don t change anything Comments and spaces inside count Each unique query text is stored just once in the DMV sys.query_store_query_text

11 Query Store DMVs overview Query_Text sys.query_store_query_text ANSI Options Query_ANSI sys.query_store_query Execution plans 1:N 1:N 1:N Query_Plan sys.query_store_plan Metrics: 1 row per plan per time interval Runtime_Stats sys.query_store_runtime_stats Context_Settings sys.query_context_settings Runtime_Stats_Interval sys.query_store_runtime_stats_interval One row per unique combination of set options One row per time interval

12 Demo environment A console application executes this query in a loop on a database where Query Store is enabled Parameters are generated by a randomized function, values are between Zero and 100 Plan cache is cleaned when parameters values are less than 2

13 SQL Server 2016 Query Store DEMO

14 Query Store tuning Because collecting data has always a cost, SQL Server allows you to tune the Query Store with these options of ALTER DATABASE statement INTERVAL_LENGTH_MINUTES MAX_STORAGE_SIZE_MB MAX_PLANS_PER_QUERY (200 by default) QUERY_CAPTURE_MODE (ALL, AUTO, NONE) DATA_FLUSH_INTERVAL_SECONDS

15 Server Upgrades Are you worried about SQL Server upgrades? This is the way out 1. Restore a copy of the production DB on a test server 2. Run a significative workload 3. Look at the Query Store for performance regressions Plan forced works across Recompilation Server reboots and failover

16 Live Query Statistics Allows you to see the live execution plan of an active query It provides a way to better understand the query execution process and the control flow It is extremely useful (and cool ) for debugging query performance It is based on sys.dm_exec_query_profiles You can use it also on SQL Server 2014 (SP1)

17 Live Query Statistics DEMO

18 Live Query Statistics on SQL 2014 (SP1) At the server side Download and install the Service Pack 1 for SQL 2014 (if you have not already done) At the client side Download and install the latest version of SSMS (Last preview) Enable the Live Query Statistics Play with it on a test machine.. SQL Server will make some effort to produce the data for this tool!

19 Summary: With Query Store you can.. Analyze your workload Easily fix plan regressions Find the most expensive queries De-risk SQL Server upgrades

20 Resources My article on Microsoft MVP Award Blog SQL Server 2016 Query Store [docs.com] SQL Server Query Store SQL Server 2016 Video Pills Live Query Statistics

21 Q&A Questions?

22 THANKS! Thanks for attending this session!

Query Store What s it all about?

Query Store What s it all about? Andrew J. Kelly Sr. Technology Subject Matter Specialist B3 Group Inc. #ITDEVCONNECTIONS ITDEVCONNECTIONS.COM Andrew J. Kelly Andrew J. Kelly is a Sr. Technology Subject