From 67b8f7666fa876b05d0bc76fb7f575f53c5bf35c Mon Sep 17 00:00:00 2001
From: Joe Sack <joe.sack@gmail.com>
Date: Thu, 27 May 2021 11:00:12 -0500
Subject: [PATCH] Query Store Hints Demo

Query Store Hints Demo
---
 .../query-store/Query Store Hints Demo.sql    | 131 ++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 samples/features/query-store/Query Store Hints Demo.sql

diff --git a/samples/features/query-store/Query Store Hints Demo.sql b/samples/features/query-store/Query Store Hints Demo.sql
new file mode 100644
index 00000000..c58e281b
--- /dev/null
+++ b/samples/features/query-store/Query Store Hints Demo.sql	
@@ -0,0 +1,131 @@
+-- ************************************************************************ --
+-- Query Store hints demo
+
+-- Demo uses "PropertyMLS" database which can be imported from BACPAC here:
+-- https://github.com/microsoft/sql-server-samples/tree/master/samples/features/query-store
+
+-- Email QSHintsFeedback@microsoft.com for questions\feedback
+-- ************************************************************************ --
+
+/*
+	Demo prep, in PropertyMLS
+*/
+
+ALTER DATABASE [PropertyMLS] SET QUERY_STORE CLEAR;
+ALTER DATABASE current SET QUERY_STORE = ON;
+ALTER DATABASE current SET QUERY_STORE  (QUERY_CAPTURE_MODE = ALL);
+GO
+
+-- Should be READ_WRITE
+SELECT actual_state_desc 
+FROM sys.database_query_store_options;
+GO
+
+/*
+	You can verify Query Store Hints in sys.query_store_query_hints.
+	Checking if any already exist (should be none).
+*/
+SELECT	query_hint_id,
+		query_id,
+		query_hint_text,
+		last_query_hint_failure_reason,
+		last_query_hint_failure_reason_desc,
+		query_hint_failure_count,
+		source,
+		source_desc
+FROM sys.query_store_query_hints;
+GO
+
+/*
+	 The PropertySearchByAgent stored procedure has a parameter
+	 used to filter AgentId.  Looking at the statistics for AgentId,
+	 you will see that there is a big skew for AgentId 101.
+*/
+SELECT	hist.range_high_key AS [AgentId], 
+		hist.equal_rows
+FROM sys.stats AS s
+CROSS APPLY sys.dm_db_stats_histogram(s.[object_id], s.stats_id) AS hist
+WHERE s.[name] = N'NCI_Property_AgentId';
+
+
+-- Show actual query execution plan to see plan compiled.
+-- Agent with many properties will have a scan with parallelism.
+EXEC [dbo].[PropertySearchByAgent] 101;
+
+-- Agents with few properties still re-use this plan (assuming no recent plan eviction).
+EXEC [dbo].[PropertySearchByAgent] 4;
+
+
+/*
+	Now let's find the query_id associated with this query.
+*/
+SELECT query_sql_text, q.query_id
+FROM sys.query_store_query_text qt 
+INNER JOIN sys.query_store_query q ON 
+	qt.query_text_id = q.query_text_id 
+WHERE query_sql_text like N'%ORDER BY ListingPrice DESC%' and query_sql_text not like N'%query_store%';
+GO
+
+/*
+	 We can set the hint associated with the query_id 
+	 Note, we can designate one or more query hints
+*/
+EXEC sp_query_store_set_hints 10, N'OPTION(RECOMPILE)';
+GO
+
+/*
+	You can verify Query Store Hints in sys.query_store_query_hints
+*/
+SELECT	query_hint_id,
+		query_id,
+		query_hint_text,
+		last_query_hint_failure_reason,
+		last_query_hint_failure_reason_desc,
+		query_hint_failure_count,
+		source,
+		source_desc
+FROM sys.query_store_query_hints;
+GO
+
+-- Execute both at the same time and show actual query execution plan.
+-- You should see two different plans, one for AgentId 101 and one for AgentId 4.
+EXEC [dbo].[PropertySearchByAgent] 101;
+EXEC [dbo].[PropertySearchByAgent] 4;
+GO
+
+SELECT	query_hint_id,
+		query_id,
+		query_hint_text,
+		last_query_hint_failure_reason,
+		last_query_hint_failure_reason_desc,
+		query_hint_failure_count,
+		source,
+		source_desc
+FROM sys.query_store_query_hints;
+GO
+
+/*
+	We can remove the hint using sp_query_store_clear_query_hints
+*/
+EXEC sp_query_store_clear_hints @query_id = 10;
+GO
+
+/*
+	That Query Store Hint is now removed
+*/
+SELECT	query_hint_id,
+		query_id,
+		query_hint_text,
+		last_query_hint_failure_reason,
+		last_query_hint_failure_reason_desc,
+		query_hint_failure_count,
+		source,
+		source_desc
+FROM sys.query_store_query_hints;
+GO
+
+-- Execute both at the same time and show actual query execution plan.
+-- You should see one plan again.
+EXEC [dbo].[PropertySearchByAgent] 101;
+EXEC [dbo].[PropertySearchByAgent] 4;
+GO
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