Kerry Walker

Software Engineer, Forgetful Blogger, Lucky Husband, Proud Father

Home About CV Dev Home Automation & Energy Referrals

© 2026. MIT License.

Never Compute an Id, Look It Up: Mapping Tables

25 Oct 2026
The obvious shortcut is to add a number to every identifier and call it done. Here is why that falls over, and what we used instead: more than forty tables whose only job was to remember what became what. More …

Writing SQL as if Both Databases Were One: Synonyms

23 Oct 2026
Every script in a migration needs to read the old system and write to the new one. Three-part names everywhere make that brittle and impossible to test. There is a tidier answer and it takes ten minutes. More …

Before You Can Migrate, You Have to Build Somewhere to Put It

21 Oct 2026
Ten years of independent development meant one system had features the other had never heard of. You cannot map a table onto a table that does not exist, so a good part of a data migration project turned out to be ordinary feature development. More …

Two Systems That Drifted Apart: Merging Databases With a Common Ancestor

19 Oct 2026
Two bespoke systems that were the same product a decade earlier, then developed independently ever since. The base tables still rhyme. Everything built since does not. This is what merging them actually involves. More …

An Action, and the Question of Whether to Offer It: The Command Pattern

14 Oct 2026
Every screen has a menu of things you can do to the record you're looking at. Packaging each one as an object is the Command pattern. The part most explanations skip is that you need a second object to say whether it should be there at all. More …
Older