Database Change Management One solution to an often complex problem Kevin Hurwitz Headspring Systems

The Problem Most significant business applications rely on at least one relational database for persisting data Most significant business applications rely on at least one relational database for persisting data As new features are developed, database schema changes are often necessary – i.e. new tables, columns, views, and stored procedures As new features are developed, database schema changes are often necessary – i.e. new tables, columns, views, and stored procedures Database schema changes and corresponding code changes must always be deployed together Database schema changes and corresponding code changes must always be deployed together While deploying software to a production environment, code files and libraries may usually be deleted or overwritten – Database files, however, must be intelligently manipulated so as not destroy vital business data While deploying software to a production environment, code files and libraries may usually be deleted or overwritten – Database files, however, must be intelligently manipulated so as not destroy vital business data

Staging Database Environment To ensure an application remains stable throughout the development lifecycle, a data-driven application must be deployed to at least two environments: Production and Staging To ensure an application remains stable throughout the development lifecycle, a data-driven application must be deployed to at least two environments: Production and Staging Database and corresponding code changes are applied and tested in the staging environment before being deployed to production Database and corresponding code changes are applied and tested in the staging environment before being deployed to production ProductionStaging Production Users DevelopersTestersSalespeopleProduct Manager

Many Database Environments While two database environments represent the bare minimum, teams become more productive when certain roles and individuals have their own copy of the database While two database environments represent the bare minimum, teams become more productive when certain roles and individuals have their own copy of the database For example, a developer may make a change to the staging database which breaks the application and derails testers and salespeople For example, a developer may make a change to the staging database which breaks the application and derails testers and salespeople Testers and salespeople may also want to work with their own set of data Testers and salespeople may also want to work with their own set of data Production Users SalespeopleDeveloper #1Developer #2Tester #1Tester #2 Demo

Database Synchronization Many development shops shy away from creating numerous database copies due to the challenge of keeping them all “in synch” Many development shops shy away from creating numerous database copies due to the challenge of keeping them all “in synch” An automated process is needed to make the process of upgrading out- of-date databases simple An automated process is needed to make the process of upgrading out- of-date databases simple Team members who maintain their own database will run the process on demand, while shared databases will be upgraded by an automated build Team members who maintain their own database will run the process on demand, while shared databases will be upgraded by an automated build Production Users SalespeopleDeveloper #1Developer #2Tester #1Tester #2 Demo Shared database upgraded by build/deployment process Individual database upgraded as needed

Incremental Schema Changes All database schemas can be thought of as a compilation of incremental changes made over time to accommodate new functionality All database schemas can be thought of as a compilation of incremental changes made over time to accommodate new functionality To automate the process developers will record all database changes as SQL scripts which they will commit to the source control repository To automate the process developers will record all database changes as SQL scripts which they will commit to the source control repository A program can then be run to execute all of the change scripts against databases which have not yet received the necessary updates A program can then be run to execute all of the change scripts against databases which have not yet received the necessary updates As updates are applied to a database, the changes will be recorded in a table similar to the following: As updates are applied to a database, the changes will be recorded in a table similar to the following: ChangeDate 1_Create_Customer_Table.sql _Add_ _address_column.sql _Add_fax_number_column.sql _Add_transaction_table.sql _Add_transaction_status_column.sql _Add_customer-transaction_view.sql

Database Schema Change Lifecycle Time Developer creates an incremental SQL change script and tests the change locally Once the change is validated by unit tests, the script is checked into source control in a special location The automated build process kicks off, runs the upgrade process which executes the change script against the integration test database, and runs all unit tests to validate the change Once the build has succeeded, the tester can get the latest version of the software from source control and run the upgrade process via a GUI to upgrade her local database Once the build has been validated by QA, automated build processes can be run to deploy the software to staging and production

Creating SQL Server Change Scripts Time Developer snapshots the current state of the database using Red Gate SQL Compare Developer makes all necessary changes to the database using SQL Server Management Studio Developers executes Red Gate SQL Compare to create a transactional change script for the change just made in SQL Server Management Studio The developer saves the Red Gate change script within the database script project under the “Update” folder The developer rebuilds the database from scratch, re- executes the database integration unit test, and commits the new script