Column type change may silently truncate data

What it is

A migration alters a column's type without a USING clause specifying how existing values convert.

Why it matters

Postgres either refuses the change or applies a default cast, which can truncate or silently reinterpret every existing row. The migration reports success either way.

How to fix it

Test the cast against a copy of production data, then add an explicit USING clause. Where values cannot convert safely, use expand-contract: add a new column, backfill it, switch reads, and drop the old one later.