“Design By Document”

I’ve only used this once but it worked perfectly. I was developing a function based on a regulatory document specifying how to build a calendar for regulatory reporting.

Normally you take a requirement and translate it in your mind to a convenient “shape” for coding. This is fine for most purposes. I started developing my procedure that way. Unfortunately the rules on how to handle holidays and non-working days were so complex I soon lost control. Continue reading

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Developer! Get a grip on your Information Information!

Good luck to anyone who can conjure up a TED lecture out of telling people that it’s impossible to keep up with all the changes these days. You and I knew that already, didn’t we?

Agile methods help organisations adapt to change. If successfully applied they increase the rate of change. There was an interesting podcast about Agile on .NET Rocks recently called The Economics, Psychology and Science of Agile. The very intelligent guest (listening at double speed was a wild ride) helps corporations improve their agility.

Individuals and teams act and react in a complicated way, so managing change and the information associated with it is hard for organisations. As a developer you are responsible for moving your knowledge forward in tandem. It’s a simpler task but not easy because you can’t call on other people to do it for you. Continue reading

Agile Continuous Delivery of Databases (3)

A phase of my Agile Blue/Green deployment project is now complete, as I have a Proof of Concept which has been tested successfully. As you may recall from prior posts, the Blue/Green technique features two databases, the “green” live one that users connect to (I’ve made an arbitrary assignment of colours), and the offline “blue” one which has a different version of the schema (a previous or future release). Continue reading

Agile Continuous Delivery of Databases (2)

{Previous Article in Series}

Most applications include a database, and the goal of the project I’m working on is to make Agile continuous delivery possible in the database as well as in procedural code. The peculiar problem with databases is that when a change deployment fails we risk losing data that has been added since the release.

The “blue-green” deployment model is a way of dealing with this. We cut over to an “old version” database. The code and schema of this database pre-date the release, but it has received all the data changes since the release.

How can this be? Continue reading

“Test-First” Database Development (2)

I’ve made additions and changes to the GitHub repository for “Test First” development of the database schema. All procedure names will now start with “Test”, so that they’re easier to find in Object Explorer and Intellisense. I’ve added a “TestHeader” stored procedure. You can put this at the top of your TDD script and it’ll add the date/time, database user, Sql Server version etc., to your results.

The spObjectExists procedure has been replaced by TestObjectExists, with the following signature:
CREATE PROCEDURE [dbo].[TestObjectExists]
@i_ObjectType sysname
,@i_ObjectName sysname = Null
,@i_ParentSchemaName sysname = Null --not needed if testing schema's existence
,@i_DbName sysname = Null
AS
Continue reading

“Test-First” Database Development (1)

I’m looking at the practicalities of using Continuous Delivery/Agile techniques where the database is a “high scale” project in Agile terms, and therefore relatively difficult (for more detail about this Agile terminology refer to Scott Ambler’s writings).

As well as thinking about the big issues, I want to start putting together some of the pieces to make it work. I’m doing this in Sql Server 2014 Transact-Sql. I’ve started with automated testing of reporting procedures. There may be utilities that can do this; finding suitable tools is part of the research. It still seems worthwhile having alternatives in Transact-Sql if possible. There’s no purchase or installation to approve, and the code is easy to understand and to edit. Continue reading

Agile Continuous Delivery of Databases (1)

Agile and Continuous Delivery techniques have been applied to databases for some time, and it’s clear they offer big advantages. Some types of application are particularly suited. They’ll be well-represented among the successes and case studies. Others, such as those including a complex relational database, don’t fit the mould quite so easily. These would be in the “Agility at Scale” category, and often in use within large enterprises.

How does our database project fit in? If Agile wouldn’t be an easy win, can we still get some benefit? I’ve been thinking about that, because the data warehouses I work on are definitely not easy wins. I’m jotting down some notes here, not a formal document, and I hope to develop my thinking in future blogs. Continue reading