Replaces ADR-0033 §2's original Node::Guard + Choice(SQL,DSL) mechanism,
which was found during 3a to be unworkable: any guard-in-Choice approach
forces a walk_choice change (walk_choice falls through only on NoMatch, so
simple-mode valid-DSL would wrongly surface "this is SQL"), and walk_seq
treats a NoMatch past idx 0 as a hard Failed, breaking advanced-mode DSL
fall-through.
Mechanism (Amendment 1): each REGISTRY entry is tagged
CommandCategory::{Simple, Advanced}, generalising the whole-command
is_advanced_only gate. walk() becomes a thin dispatcher over decide()
(mode-aware candidate selection: simple commits the DSL node or emits the
"this is SQL" hint; advanced tries SQL first, DSL as a full-line fallback)
and an extracted walk_one_command(); speculative match-testing runs on a
scratch WalkContext so the caller's context is only touched by the
committed walk. No Node::Guard, no walk_choice/walk_seq change.
6 dispatch smoke tests on a shared-entry-word smoke registry; 1446 baseline
green; clippy clean.
Phase 3 of ADR-0030's SQL-surface roadmap. Status: Proposed.
Statement shapes (§1): single- and multi-row INSERT, INSERT…SELECT
(recursing through ADR-0032's SQL_SELECT_COMPOUND), UPDATE with
SET assignment list, DELETE, all three optionally followed by
RETURNING projection_list. Full UPSERT (ON CONFLICT … DO NOTHING /
DO UPDATE with the SQLite/PostgreSQL `excluded` pseudo-table)
on INSERT.
Dispatch (§2): SQL-first / DSL-fallback in Advanced mode via
Choice(SQL_shape, DSL_shape) per shared entry word. Requires a
new walker capability — Node::Guard(fn), a zero-byte-consumption
gating node — landed as the first sub-phase's work (R1 mitigation
budgeted).
Execution (§10): three typed Command variants (SqlInsert /
SqlUpdate / SqlDelete) carrying target_table, listed_columns,
and a returning: bool flag. Worker handlers know per-kind
specialisations: shortid auto-fill (§6, parity with DSL),
cascade summary (§7, WHERE byte-range injection into pre-count
subqueries), DataResult routing on RETURNING (§5).
Diagnostics (§8): three new keys (insert_arity_mismatch ERROR,
auto_column_overridden WARNING, not_null_missing WARNING) with
positive + negative test requirements.
OOS list (§13): DEFAULT VALUES (seed feature), SQLite OR-prefixes,
UPDATE FROM, WITH-prefixed DML, indexed-by hints,
multi-statement batches.
Implementation notes: eleven phased sub-phases (3a–3k) each with
explicit exit gates + written DA gates. Ordering puts Node::Guard
scaffolding (3a) FIRST so the dispatch mechanism is proven before
DML grammar lands on top.
Initial DA review (Initial DA review section) recorded seven
critiques that were resolved before status moved to Proposed; a
second-pass DA surfaced an eighth (Node::Guard wasn't an
existing walker capability) and added it to §2 + sub-phase 3a's
scope.
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