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parser: existential subquery brace form EXISTS { pattern } (+2 TCK) #86

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Merged
dylanbstorey merged 1 commit into from
May 29, 2026
Merged

parser: existential subquery brace form EXISTS { pattern } (+2 TCK) #86

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14 changes: 14 additions & 0 deletions docs/testing/semantic-coverage-matrix.md
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Original file line number Diff line number Diff line change
Expand Up @@ -385,3 +385,17 @@ unit 944/944; functional clean):
Added a mirror rule chaining four `make_label_expr` conjuncts. Repeated labels
are harmless — each conjunct is an independent EXISTS check. No bison conflicts
(still `%expect 15` / `%expect-rr 3`).

## Coverage update (2026-05-28) — existential subquery brace form (no inner WHERE)

`cypher_gram.y`. Verified via the TCK harness (3708 -> 3710, zero regressions;
unit 944/944; functional clean):

- **`WHERE exists { (n)-->() }` parses and evaluates** (ExistentialSubquery1
[1]/[3]). Added `EXISTS '{' pattern_list '}'` reusing the existing
`EXISTS_TYPE_PATTERN` transform, which already resolves correlated outer
variables (the bound `n`) via its outer-alias lookup and emits a correlated
`EXISTS (SELECT 1 FROM ... WHERE ...)` subquery. No bison conflicts (still
`%expect 15` / `%expect-rr 3`). The brace form **with** an inner `WHERE`
([2]/[4]) and the full-query/aggregation/nested forms (ExistentialSubquery2/3)
remain unsupported — they need inner-variable registration and are deferred.
8 changes: 8 additions & 0 deletions src/backend/parser/cypher_gram.y
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Expand Up @@ -1500,6 +1500,14 @@ function_call:
/* EXISTS((pattern)) - check for relationship/path existence */
$$ = (ast_node*)make_exists_pattern_expr($3, @1.first_line);
}
| EXISTS '{' pattern_list '}'
{
/* Existential subquery brace form: EXISTS { (n)-->() }
* (ExistentialSubquery1 [1]/[3]). Reuses the pattern-existence
* transform; correlated outer variables resolve via the
* EXISTS_TYPE_PATTERN emitter's outer-alias lookup. */
$$ = (ast_node*)make_exists_pattern_expr($3, @1.first_line);
}
| EXISTS '(' IDENTIFIER '.' IDENTIFIER ')'
{
/* EXISTS(n.property) - unambiguous property existence check */
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