3 posts tagged with "Migration"

Copying tables into a lakehouse is the easy part. The hard part is whether 0 means zero or was null in the legacy system, and whether a 0.01 drift is rounding or a bug.

I treat migration as a semantic contract, not a file move. Stakeholders do not celebrate that Delta exists. They celebrate that last month's margin still matches within agreed rules.

Figure 1. Shortcuts and schemas change where data appears, not what it means. Source: Microsoft Learn: lakehouse schemas.

A migration checklist that only compares row counts will greenlight wrong money, wrong dates, and wrong statuses. Row counts catch catastrophic drops. They miss the quiet CAST that turns decimals into floats, the null that became empty string, and the column that silently defaulted.

Push MLV cutovers to per-column tables and type-aware aggregates. Borrow the tiered reconciliation classical data migrations already trust: rows, then keys, then column aggregates. Automate it. Treat the artifacts as release evidence, not as a screenshot buried in chat.

Figure 1. Row counts catch catastrophes. Column aggregates and quality reports catch the quiet CAST that breaks money. Source: Microsoft Learn: MLV data quality reports.

Figure 2. Treat per-column reconciliation artifacts as release evidence for MLV cutovers, not optional notebook scratch. Source: Microsoft Learn: MLV data quality reports.

Moving a handful of warehouse views to Materialized Lake Views is a rewrite. Moving hundreds is a program. Teams that treat the long tail like a weekend notebook usually discover dependency order the hard way: gold breaks, silver thrashes, and bronze shortcuts were never registered as the real contract.

Frame the work as bronze to silver to gold with gates. Count the estate. Order by dependency. Prove a representative POC. Then convert with per-view notebooks so blast radius stays local. Success is parity plus runtime, not "the portal shows an MLV."

Figure 1. MLV migration is a program across bronze, silver, and gold. Gates belong between layers, not as a weekend cutover wish. Source: Microsoft Learn: medallion lakehouse architecture.