Introduce new DeleteConsecutiveAttributes maintenance procedure

In older versions of the OnTopic Library, new attribute versions could be saved even if their value had not changed. This isn't necessary in terms of the OnTopic library, which will take whatever the latest version of an attribute is when loading the topic graph (or restoring a topic). As such, these _consecutive duplicates_ only add clutter to the database, and potentially slow down some queries by introducing more data to sort through. The `DeleteConsecutiveAttributes` identifies and deletes these from the database, thus making it more efficient.

Author: JeremyCaney

OnTopic.Data.Sql.Database/Maintenance/DeleteConsecutiveAttributes.sql

@@ -0,0 +1,69 @@
+--------------------------------------------------------------------------------------------------------------------------------
+-- DELETE CONSECUTIVE ATTRIBUTES
+--------------------------------------------------------------------------------------------------------------------------------
+-- Current versions of the OnTopic Library evaluate whether or not an attribute value has changed since the previous version,
+-- and doesn't create a new attribute version if it has. This wasn't true in previous versions, however. As a result, there are
+-- some cases, and especially in older databases, where unnecessary duplicates occur for attribute values. This script will
+-- detect concurrent duplicates and remove them from the database. This reduces the size of the database, without interfering
+-- with the data integrity. If attribute values are not consecutive, the duplicates aren't deleted; e.g., if the value of
+-- <c>Title</c> gets changed, then gets reverted, all three versions will be retained in the database.
+--------------------------------------------------------------------------------------------------------------------------------
+
+CREATE PROCEDURE [dbo].[DeleteConsecutiveAttributes]
+AS
+
+SET NOCOUNT ON;
+
+--------------------------------------------------------------------------------------------------------------------------------
+-- CHECK INITIAL VALUES
+--------------------------------------------------------------------------------------------------------------------------------
+DECLARE	@Count	INT
+
+SELECT	@Count	= Count(TopicID)
+FROM	Attributes
+
+Print('Initial Count: ' + CAST(@Count AS VARCHAR) + ' Attributes in the database.');
+
+--------------------------------------------------------------------------------------------------------------------------------
+-- IDENTIFY GROUPS OF CONCURRENT DUPLICATES
+--------------------------------------------------------------------------------------------------------------------------------
+WITH GroupedValues AS (
+  SELECT	TopicID,
+	AttributeKey,
+	AttributeValue,
+	DateModified,
+	Version,
+	ValueGroup = ROW_NUMBER() OVER(PARTITION BY TopicID, AttributeKey ORDER BY TopicID, AttributeKey, Version)
+	- ROW_NUMBER() OVER(PARTITION BY TopicID, AttributeKey, AttributeValue ORDER BY TopicID, AttributeKey, Version)
+   FROM	Attributes
+),
+
+--------------------------------------------------------------------------------------------------------------------------------
+-- RANK DUPLICATES BY DATE
+--------------------------------------------------------------------------------------------------------------------------------
+RankedValues AS (
+  SELECT	TopicID,
+	AttributeKey,
+	AttributeValue,
+	DateModified,
+	Version,
+	ValueGroup,
+	ValueRank = ROW_NUMBER() OVER(PARTITION BY ValueGroup, TopicID, AttributeKey, AttributeValue ORDER BY TopicID, AttributeKey, Version)
+  FROM	GroupedValues
+)
+
+--------------------------------------------------------------------------------------------------------------------------------
+-- DELETE NEWER DUPLICATES
+--------------------------------------------------------------------------------------------------------------------------------
+DELETE
+FROM	RankedValues
+WHERE	ValueRank > 1;
+
+--------------------------------------------------------------------------------------------------------------------------------
+-- CHECK FINAL VALUES
+--------------------------------------------------------------------------------------------------------------------------------
+SELECT	@Count	= @Count - Count(TopicID)
+FROM	Attributes
+
+Print('Final Count: ' + CAST(@Count AS VARCHAR) + ' Attributes were identified and deleted.')
+

OnTopic.Data.Sql.Database/OnTopic.Data.Sql.Database.sqlproj

@@ -100,6 +100,7 @@
     <Build Include="Types\AttributeValues.sql" />
     <Build Include="Types\TopicList.sql" />
     <Build Include="Views\AttributeIndex.sql" />
+    <Build Include="Maintenance\DeleteConsecutiveAttributes.sql" />
   </ItemGroup>
   <ItemGroup>
     <ArtifactReference Include="$(DacPacRootPath)\Extensions\Microsoft\SQLDB\Extensions\SqlServer\130\SqlSchemas\master.dacpac">