The Hoarder's Warehouse (Touch a Table, Take a Table)
The Problem
You hear it all the time from data engineers: "Touch a table, take a table." Sounds efficient, right? Just ingest the whole thing, every column, every row. Easy. Except now your data warehouse is a hoarder's nightmare. You've got 847 columns across 50 tables and nobody knows what 80% of them are. "customer_legacy_flag_2" sits there taking up space, covered in metaphorical cobwebs, never used in a single dashboard or analysis. But you're paying to store it. You're paying to process it. And worse—it's cluttering your shelves, making it harder for analysts to find what they actually need. It's like a manufacturing plant storing every scrap of raw material that ever entered the building "just in case." Meanwhile, the useful materials are buried under junk and workers waste hours digging through garbage to find what they need.
The Principle
Be ruthlessly focused: only pull in columns you'll actually use for the current use case. Yes, this requires thinking upfront. Yes, it's harder than "take everything." But it's the manufacturing mindset—you don't stock raw materials you don't have orders for. Before ingesting a table, ask: "Which specific columns will we use in reports, dashboards, or models?" Pull those. Document why. Then design your layering methodology (raw → staging → core → analytics) so adding columns later is trivial when they're truly needed. And "needed" means "will be used," not "might be useful someday." The 80/20 rule applies: 80% of columns never get used. Don't pay to store, process, and maintain them. The magic happens when your data warehouse is clean, focused, and every column has a purpose. Analysts find what they need in seconds instead of minutes. Costs drop. Speed increases. Less is more.
3 Steps to Take Action
Audit Column Usage: Query your data warehouse. Which columns get used in joins, reports, models? Flag anything unused in 12 months for deletion.
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