Module drift 

Schema-drift detection + policy types (issue #194).

Drift is the divergence between an incoming page’s inferred top-level shape (via crate::schema::infer_schema) and the sink’s live destination schema (via crate::Sink::current_schema). The pure diff_schema classifies each top-level column into one bucket; SchemaDriftPolicy decides what the pipeline does with the result. Nested objects are treated as a single column.

Structs

ColumnChange

One column’s drift, expressed in JSON-Schema type-fragment terms (e.g. {"type":"integer"} or {"type":["string","null"]}).

SchemaDiff

Result of diffing a page’s inferred shape against the destination schema.

SchemaDriftPolicy

Compiled, ready-to-run drift policy. Cheap to clone.

SchemaDriftSpec

User-facing schema: config block (pipeline level).

SchemaEvolution

The applyable subset of a SchemaDiff handed to crate::Sink::evolve_schema. Never carries incompatible columns — those are routed by the policy.

Enums

OnDrift

What to do when drift is detected.

OnIncompatible

evolve-only: what to do with a narrowing/incompatible change that can’t be auto-applied.

SqlBaseType

Backend-neutral base column type inferred from a JSON-Schema fragment. Each SQL sink maps these to its concrete keyword.

Functions

adds_null

True when to permits null but from does not — the column needs its NOT NULL constraint relaxed.

base_widened

True when the non-null base type family changes from from to to (after the integer→number collapse) — i.e. the column needs an ALTER TYPE.

diff_schema

Diff a page’s inferred shape against the destination schema (top-level columns).

json_schema_base_type

Map a top-level JSON-Schema type fragment to a base SQL type, or None for a pure-null fragment (caller falls back to TEXT/NVARCHAR for an added column whose only observed value was null).