Advanced-only `alter` entry word; ALTER TABLE <T> ADD COLUMN <col> <type>
[constraints] | DROP COLUMN <col> | RENAME COLUMN <old> TO <new> ->
SqlAlterTable, runtime-decomposed to the existing column executors
(do_add_column / do_drop_column / do_rename_column) — one undo step each,
no new worker layer. The COLUMN keyword is required (reserves bare
RENAME TO for 4h, ADD CONSTRAINT for 4g).
- ADD COLUMN takes NOT NULL / UNIQUE / DEFAULT / CHECK (no PK / inline
REFERENCES). do_add_column extended to consume the SQL raw-text
default_sql / check_sql (sql_expr is validate-only, the 4a.2
mechanism), reaching parity with CREATE TABLE's column constraints.
- Drop/rename column refuse a column any CHECK references — table-level
AND column-level (incl. a column's own self-check on rename) — the
4a.3 deferral, detected up-front by tokenizing the raw CHECK text
(skipping string literals). In the shared executors, so it guards both
the simple and SQL surfaces and fixes a latent rename-drift bug that
desynced the stored CHECK text and broke rebuild.
- SQL DROP COLUMN refuses an index-covered column (no --cascade SQL
spelling — matches SQLite + the simple default).
- The column executors and do_add_index gained an internal-__rdbms_*
guard (refuse as "no such table"), closing a pre-existing exposure on
both surfaces. (do_change_column_type / do_add_constraint /
do_add_relationship are a tracked follow-up.)
- `alter` is advanced-only; AlterTableAction::AddColumn is boxed
(clippy::large_enum_variant).
Docs: ADR-0035 status + §13 4e; ADR README; requirements.md Q1. Plan:
docs/plans/20260525-adr-0035-sql-ddl-4e.md.
Tests: 1854 passing / 0 failing / 0 skipped / 1 ignored; clippy clean.
claude@clouddev1