ALTER TABLE <T> ADD [CONSTRAINT <name>] (CHECK | UNIQUE | FOREIGN KEY)
and DROP CONSTRAINT <name>. ADD = table-CHECK + composite UNIQUE + FK
(ADD PRIMARY KEY and a named UNIQUE refused — composite UNIQUE is
anonymous in our model). Each ADD reuses a low-level path with a dry-run
guard (table-CHECK/UNIQUE rebuild; FK -> add_relationship, bare
REFERENCES -> parent single PK). DROP CONSTRAINT resolves the name to a
named table-CHECK then a child-side FK, else refuses. One undo step each.
Named table-CHECKs round-trip: a nullable `name` column on
__rdbms_playground_table_checks (rebuild-only arrival; a named add on a
pre-4g project is refused with a "rebuild first" hint) plus a project.yaml
check_constraints {expr, name} extension (bare-string form still reads).
The internal-__rdbms_* guard was folded into do_add_constraint /
do_add_relationship, completing that guard class.
Grammar: the action Choice keeps one branch per verb (add/drop/rename/
alter) with an inner Choice fanning out on the distinct second keyword,
since the walker's Choice does not backtrack between same-led branches.
Tests: 7 Tier-1 parse + 2 yaml round-trip + 1 internal-guard + 9 Tier-3
e2e. Help/usage refreshed; ADR-0035 §13 4g + README + requirements.md in
lockstep.
Fourth AlterTableAction (AlterColumnType), runtime-decomposed to the
existing change_column_type executor with ForceConversion — which IS the
§7 advanced policy: lossy converts with a note (no force flag),
incompatible + the ADR-0017 static refusals (↔blob, same-type,
date↔datetime, non-int→serial) still refuse, while int→serial is allowed
(auto-fills nulls + UNIQUE, ADR-0018 §8). No new mode/note/persistence;
undo is the advanced safety net.
Grammar adds a fourth action branch leading on `alter`, discriminated in
the builder by the `type` keyword (unique — ADD COLUMN's type is an
ident); the type slot reuses SQL_TYPE. The internal-__rdbms_* guard was
folded into do_change_column_type (user-confirmed), closing the simple
`change column` exposure.
Tests: 7 Tier-3 e2e via run_replay + 4 Tier-1 parse (incl. a column-named-
`type` discriminator probe) + the simple-surface guard. Help/usage
refreshed; ADR-0035 §13 4f + README + requirements.md in lockstep.
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