How to track data lineage with SQL Server Graph Tables – Part 2 Create Database Procedures

This is my second post in a series which explains how to use SQL Server Graph Tables to track data lineage.

In my previous post I covered creating the node and edges tables required to store data lineage. In this post I will show you how to create database procedures in order to simplify the process of populating the graph tables. These procedures are deliberately basic so that they are easy to understand but they are also easily extensible and can serve as the starting point for a more sophisticated solution.

Overview

Before diving into the code it is always good to have a conceptual understanding of the process. The flowchart below explains the logic of these procedures.

As you can see in the diagram above, we check if the source or target is new and then based on the condition create the appropriate nodes and edges. In order to avoid duplicating code we will create a procedure for creating the nodes and the edges and then call theses sub processes from a parent process that controls the logic flow.

Create Nodes Procedure

First, we will create a procedure to populate our node table. As you recall from the previous post our node table is called [dbo].[DataEntity].

DROP PROCEDURE IF EXISTS dbo.Create_Nodes
GO

CREATE PROCEDURE dbo.Create_Nodes

    @ColumnList VARCHAR(MAX),
    @Table VARCHAR(MAX),
    @Database VARCHAR(MAX),
    @System VARCHAR(MAX)

AS
BEGIN
    SET NOCOUNT ON;
    DECLARE @NodeIDs TABLE (ID NVARCHAR(1000));

    --Insert data ino Node table and keep Source IDS so that we can populate the Edge table
    INSERT INTO [dbo].[DataEntity]
    OUTPUT INSERTED.$NODE_ID AS TOID INTO @NodeIDs(ID)
    SELECT
        value AS [ColumnName],
        @Table AS [TableName],
        @Database AS [DatabaseName],
        @System AS [SystemName],
        GETDATE() AS [CreatedDt]

    FROM  
        STRING_SPLIT(@ColumnList, ',');

    SELECT ID FROM @NodeIDs;    
    RETURN 
END

Now that we have a procedure to create our nodes, we will create another procedure to create the edges.

Create Edges Procedure

We need to pass a list of procedure a list of node ids to insert into the [dbo].[DataFlowsTo] table so we will create a user defined type to store and pass this information.

/* Create a table type in order to pass a list of Node IDs to this procedure*/
DROP TYPE IF EXISTS dbo.NodeIDTableType
CREATE TYPE dbo.NodeIDTableType  AS TABLE  ( ID NVARCHAR(1000) );

GO

After the user defined table type is created we can create the procedure to populate the edge table.

DROP PROCEDURE IF EXISTS dbo.Create_Edges
GO

CREATE PROCEDURE dbo.Create_Edges

    @Source  NodeIDTableType READONLY,
    @Target  NodeIDTableType READONLY,
    @Process VARCHAR(MAX)
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

   --Get the FROM and TO node ids into a common table exppression and populate the edge table in batch.
   */
   
    WITH CTE (TOID, FROMID) AS
    (
        SELECT 
            A.FROMID,
            B.TOID
        FROM
            (SELECT ID AS FROMID, ROW_NUMBER() OVER(ORDER BY ID ASC) as RowNum FROM @Source) as A
        JOIN 
            (SELECT ID AS TOID, ROW_NUMBER() OVER(ORDER BY ID ASC) as RowNum FROM @Target) as B
        ON A.RowNum = B.RowNum
    )
    
    --Insert Lineage data into DataFlowsTo Edge table
     INSERT INTO [dbo].[DataFlowsTo] ($from_id, $to_id, ProcessName)
     SELECT CTE.TOID, CTE.FROMID, @Process FROM CTE;

    
END

In case you are wondering I used a common table expression (CTE) so that the edge records could be created in bulk rather than one at a time.

Create Data Lineage Procedure

This is the final procedure which checks to see if the source or target is new and calls the procedures above as required. The conditional logic check is premised on the assumption a the combination of system name, database name, table name and column name is unique.

DROP PROCEDURE IF EXISTS dbo.Create_Data_Lineage
GO
USE [DataLineage]
GO


CREATE PROCEDURE [dbo].[Create_Data_Lineage] 

    --Source data
    @SourceSystem VARCHAR(MAX),
    @SourceDatabase VARCHAR(MAX),
    @SourceTable VARCHAR(MAX),
    @SourceColumnList VARCHAR(MAX),

    --Target data
    @TargetSystem VARCHAR(MAX),
    @TargetDatabase VARCHAR(MAX),
    @TargetTable VARCHAR(MAX),
    @TargetColumnList VARCHAR(MAX),

    @ProcessName VARCHAR(MAX)

AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

        
    --DECLARE @SourceIDs TABLE (ID NVARCHAR(1000));
    --DECLARE @TargetIDs TABLE (ID NVARCHAR(1000));
    
    DECLARE @SourceIDs NodeIDTableType;
    DECLARE @TargetIDs NodeIDTableType;

    
    --Prepare the list of fields by removing any spaces or tabs between the comma seperated list of source and target columns
    SET @SourceColumnList = REPLACE(REPLACE(@SourceColumnList,' ', ''), char(9), '');
    SET @TargetColumnList = REPLACE(REPLACE(@TargetColumnList,' ', ''), char(9), '');

    --Check for existing sources , if found use those id's otherwise create new nodes and use new IDs
    INSERT INTO @SourceIDs
    SELECT 
        $NODE_ID
    FROM 
        [dbo].[DataEntity] DE
    INNER JOIN 
            (SELECT
                value AS [ColumnName],
                @SourceTable AS [TableName],
                @SourceDatabase AS [DatabaseName],
                @SourceSystem AS [SystemName]
            FROM  
                STRING_SPLIT(@SourceColumnList, ',')
            ) SRC
    ON
        DE.[ColumnName] = SRC.[ColumnName]
    AND 
        DE.[TableName] = SRC.[TableName]
    AND
        DE.[DatabaseName] = SRC.[DatabaseName]
    AND
        DE.[SystemName] = SRC.[SystemName];

    --Check for existing  targets, if found use those id's otherwise create new nodes and use new IDs
    INSERT INTO @TargetIDs
    SELECT 
        $NODE_ID
    FROM 
        [dbo].[DataEntity] DE
    INNER JOIN 
            (SELECT
                value AS [ColumnName],
                @TargetTable AS [TableName],
                @TargetDatabase AS [DatabaseName],
                @TargetSystem AS [SystemName]
            FROM  
                STRING_SPLIT(@TargetColumnList, ',')
            ) TRGT
    ON
        DE.[ColumnName] = TRGT.[ColumnName]
    AND 
        DE.[TableName] = TRGT.[TableName]
    AND
        DE.[DatabaseName] = TRGT.[DatabaseName]
    AND
        DE.[SystemName] = TRGT.[SystemName];

    IF (NOT EXISTS (SELECT 1 FROM @SourceIDs)) AND (NOT EXISTS (SELECT 1 FROM @TargetIDs))
        BEGIN

            --Create source nodes
            INSERT @SourceIDs
            EXEC  dbo.CREATE_NODES 
                    @System = @SourceSystem,
                    @Database = @SourceDatabase,
                    @Table = @SourceTable,
                    @ColumnList = @SourceColumnList;
        
            --Create target nodes
            INSERT @TargetIDs
            EXEC  dbo.CREATE_NODES 
                    @System = @TargetSystem,
                    @Database = @TargetDatabase,
                    @Table = @TargetTable,
                    @ColumnList = @TargetColumnList;
        
        
            --Create edges between source and target
            EXEC dbo.Create_Edges @Source = @SourceIDs, @Target = @TargetIDs, @Process = @ProcessName;
        END
    ELSE IF (EXISTS (SELECT 1 FROM @SourceIDs)) AND (NOT EXISTS (SELECT 1 FROM @TargetIDs))
        BEGIN
        
            --create target nodes
            INSERT @TargetIDs
            EXEC  dbo.CREATE_NODES 
                    @System = @TargetSystem,
                    @Database = @TargetDatabase,
                    @Table = @TargetTable,
                    @ColumnList = @TargetColumnList;

            --Create edges between source and target
            EXEC dbo.Create_Edges @Source = @SourceIDs, @Target = @TargetIDs, @Process = @ProcessName;
        END
    ELSE IF (NOT EXISTS (SELECT 1 FROM @SourceIDs)) AND (EXISTS (SELECT 1 FROM @TargetIDs))
        BEGIN
        
            --create source nodes
            INSERT @SourceIDs
            EXEC  dbo.CREATE_NODES 
                    @System = @SourceSystem,
                    @Database = @SourceDatabase,
                    @Table = @SourceTable,
                    @ColumnList = @SourceColumnList;

            --Create edges between source and target
            EXEC dbo.Create_Edges @Source = @SourceIDs, @Target = @TargetIDs, @Process = @ProcessName
        END
    ELSE 
        --No new nodes required
        --Create edges between source and target
        EXEC dbo.Create_Edges @Source = @SourceIDs, @Target = @TargetIDs, @Process = @ProcessName
    

END
GO

Summary

In this article we have created the database procedures to simplify the process of creating the necessary node and edge records to capture data lineage between source and target fields.

In the next article I will cover how to call these procedures and query the graph tables to answer data lineage questions.

Hopefully you have found this to be another practical post.

Until next time.

Anthony

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Last updated March 15, 2019.

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