GeezerVison

Run against widely used public schemas (AdventureWorks, Pagila, GitLab's
structure.sql, pgvector), PostgreSQL migrations were wrong in six ways the
synthetic corpus had no case for.

- An array column was written as the catalog's internal name, `_varchar`:
  varchar(20)[] became varchar[], numeric(10,2)[] numeric[], bit(4)[]
  bit(1)[], and an array of a mixed-case or non-public type (`_Mood`,
  `_status`) did not resolve. The re-diff then compared the same internal
  names and called the columns identical. Arrays are now spelled by the
  server, format_type(atttypid, atttypmod).
- A type modifier on an extension type was dropped: vector(1536) became
  vector, on which an HNSW index fails ("column does not have dimensions").
- A domain in `public` was written bare. `"Name"` folded to PostgreSQL's own
  `name` type, so its columns were created with a different type, and
  `"Flag"` failed as unknown. It is quoted wherever it needs to be.
- A changed domain was dropped and recreated, which fails while any column
  uses it. A default, NOT NULL or CHECK change is now made with ALTER DOMAIN;
  only a new base type or collation still replaces it.
- A NOT VALID check was written into CREATE DOMAIN, which does not accept
  it. It is added after the domain exists, still unvalidated.
- A column added to a partitioned table was also added to every partition,
  which PostgreSQL refuses ("cannot add column to a partition"); a column a
  table only inherits is no longer added or dropped on it. And a partition in
  another schema than its parent named the parent in its own schema.

MySQL, SQLite and Dolt are unaffected: every change is in PostgreSQL-only
code, and the shared TableSchema path only skips columns PostgreSQL reports
as inherited, which other engines never do.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

PostgreSQL 18 adds virtual generated columns, and makes them the default.
Every generated column was written STORED, so a virtual one was created
stored, and the comparison could not tell them apart: the kind was not in
the pre-scan hash, the column definition parser skipped the keyword, and a
change between the two was not a regeneration.

The kind is now read from attgenerated, written as VIRTUAL or STORED, hashed,
and compared; a change between them drops and re-adds the column, as
PostgreSQL cannot switch it in place. A generated column recreated around a
dependency's retype keeps its kind.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

GitLab's `uploads` takes its id from a sequence it owns, and every partition
carries a copy of the default. Counted as further uses, those copies made the
sequence look shared, so it was modelled standalone and created — while the
column was still written bigserial, which made a second sequence
(`uploads_id_seq1`) that every partition's default then pointed at. A default
on a column the table inherits is no longer counted.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

Keeps PostgresSchemaHelper within the 20-method limit; no behaviour change.

Co-Authored-By: Claude Opus 5.5 <[email protected]>