# Architecture Decisions

## Required columns on newly created tables

**Decision.** The `NOT_NULL` SQL check accepts `ALTER TABLE ... ADD COLUMN ... NOT NULL`
only when the same migration unconditionally created that exact table. `CREATE TABLE IF
NOT EXISTS`, SQL inserts, and data operations, including nested
`SeparateDatabaseAndState` operations, do not prove an empty table. The migration remains fully
linted, so top-level and nested `RunSQL` and `RunPython`, and operations on existing tables retain
their checks. Custom database operations are not trusted as declarative schema operations and
therefore invalidate the proof. Table renames also invalidate it because a name can be reused by a
populated table.

**Rejected.** Ignoring all initial migrations or naming them as exemptions. Either option
skips unsafe operations that the linter must inspect.