gregfelice commented on code in PR #2359:
URL: https://github.com/apache/age/pull/2359#discussion_r3089614988
##########
src/backend/parser/cypher_clause.c:
##########
@@ -1602,6 +1611,331 @@ static Query
*transform_cypher_list_comprehension(cypher_parsestate *cpstate,
return query;
}
+/*
+ * Helper: build a BooleanTest node (pred IS TRUE, pred IS FALSE, etc.)
+ */
+static Node *make_boolean_test(Node *arg, BoolTestType testtype)
+{
+ BooleanTest *bt = makeNode(BooleanTest);
+
+ bt->arg = (Expr *) arg;
+ bt->booltesttype = testtype;
+ bt->location = -1;
+
+ return (Node *) bt;
+}
+
+/*
+ * Helper: build a fully-transformed bool_or(expr) Aggref node.
+ *
+ * The argument must already be a transformed boolean expression.
+ * We construct the Aggref manually to avoid going through FuncCall
+ * + transformExpr, which expects raw parse tree nodes.
+ */
+static Node *make_bool_or_agg(ParseState *pstate, Node *arg)
+{
+ Aggref *agg;
+ TargetEntry *te;
+ Oid bool_or_oid;
+ Oid argtypes[1] = { BOOLOID };
+
+ /* Look up bool_or(boolean) */
+ bool_or_oid = LookupFuncName(list_make1(makeString("bool_or")),
+ 1, argtypes, false);
+
+ /* Build the TargetEntry for the aggregate argument */
+ te = makeTargetEntry((Expr *) arg, 1, NULL, false);
+
+ /* Construct the Aggref */
+ agg = makeNode(Aggref);
+ agg->aggfnoid = bool_or_oid;
+ agg->aggtype = BOOLOID;
+ agg->aggcollid = InvalidOid;
+ agg->inputcollid = InvalidOid;
+ agg->aggtranstype = InvalidOid; /* filled by planner */
+ agg->aggargtypes = list_make1_oid(BOOLOID);
+ agg->aggdirectargs = NIL;
+ agg->args = list_make1(te);
+ agg->aggorder = NIL;
+ agg->aggdistinct = NIL;
+ agg->aggfilter = NULL;
+ agg->aggstar = false;
+ agg->aggvariadic = false;
+ agg->aggkind = AGGKIND_NORMAL;
+ agg->aggpresorted = false;
+ agg->agglevelsup = 0;
+ agg->aggsplit = AGGSPLIT_SIMPLE;
+ agg->aggno = -1;
+ agg->aggtransno = -1;
+ agg->location = -1;
+
+ /* Register the aggregate with the parse state */
+ pstate->p_hasAggs = true;
+
+ return (Node *) agg;
+}
+
+/*
+ * Helper: build a transformed CASE expression implementing three-valued
+ * predicate logic for all(), any(), and none().
+ *
+ * any(): CASE WHEN bool_or(pred IS TRUE) THEN true
+ * WHEN bool_or(pred IS NULL) THEN NULL
+ * ELSE false END
+ *
+ * all(): CASE WHEN bool_or(pred IS FALSE) THEN false
+ * WHEN bool_or(pred IS NULL) THEN NULL
+ * ELSE true END
+ *
+ * none(): CASE WHEN bool_or(pred IS TRUE) THEN false
+ * WHEN bool_or(pred IS NULL) THEN NULL
+ * ELSE true END
+ *
+ * Empty list: both bool_or calls return NULL (no rows), so the CASE
+ * falls through to the default: false for any(), true for all()/none().
+ * This matches Cypher's vacuous truth semantics.
+ */
+static Node *make_predicate_case_expr(ParseState *pstate, Node *pred,
+ cypher_predicate_function_kind kind)
+{
+ CaseExpr *cexpr;
+ CaseWhen *when1, *when2;
+ Node *bool_or_first, *bool_or_null;
+ Node *true_const, *false_const, *null_const;
+
+ /* boolean constants */
+ true_const = makeBoolConst(true, false);
+ false_const = makeBoolConst(false, false);
+ null_const = makeBoolConst(false, true); /* isnull = true */
+
+ /* Second branch is common to all: bool_or(pred IS NULL) -> NULL */
+ bool_or_null = make_bool_or_agg(pstate,
+ make_boolean_test(pred, IS_UNKNOWN));
+
+ when2 = makeNode(CaseWhen);
+ when2->expr = (Expr *) bool_or_null;
+ when2->result = (Expr *) null_const;
+ when2->location = -1;
+
+ if (kind == CPFK_ALL)
+ {
+ /* bool_or(pred IS FALSE) -> false */
+ bool_or_first = make_bool_or_agg(pstate,
+ make_boolean_test(pred, IS_FALSE));
+ when1 = makeNode(CaseWhen);
+ when1->expr = (Expr *) bool_or_first;
+ when1->result = (Expr *) false_const;
+ when1->location = -1;
+
+ cexpr = makeNode(CaseExpr);
+ cexpr->casetype = BOOLOID;
+ cexpr->arg = NULL;
+ cexpr->args = list_make2(when1, when2);
+ cexpr->defresult = (Expr *) true_const;
+ cexpr->location = -1;
+ }
+ else if (kind == CPFK_ANY)
+ {
+ /* bool_or(pred IS TRUE) -> true */
+ bool_or_first = make_bool_or_agg(pstate,
+ make_boolean_test(pred, IS_TRUE));
+ when1 = makeNode(CaseWhen);
+ when1->expr = (Expr *) bool_or_first;
+ when1->result = (Expr *) true_const;
+ when1->location = -1;
+
+ cexpr = makeNode(CaseExpr);
+ cexpr->casetype = BOOLOID;
+ cexpr->arg = NULL;
+ cexpr->args = list_make2(when1, when2);
+ cexpr->defresult = (Expr *) false_const;
+ cexpr->location = -1;
+ }
+ else /* CPFK_NONE */
+ {
+ /* bool_or(pred IS TRUE) -> false */
+ bool_or_first = make_bool_or_agg(pstate,
+ make_boolean_test(pred, IS_TRUE));
+ when1 = makeNode(CaseWhen);
+ when1->expr = (Expr *) bool_or_first;
+ when1->result = (Expr *) false_const;
+ when1->location = -1;
+
+ cexpr = makeNode(CaseExpr);
+ cexpr->casetype = BOOLOID;
+ cexpr->arg = NULL;
+ cexpr->args = list_make2(when1, when2);
+ cexpr->defresult = (Expr *) true_const;
+ cexpr->location = -1;
+ }
+
+ return (Node *) cexpr;
+}
+
+/*
+ * Transform a cypher_predicate_function node into a query tree.
+ *
+ * Generates aggregate-based queries that preserve Cypher's three-valued
+ * NULL semantics. The grammar layer wraps the SubLink with a
+ * CASE WHEN list IS NULL THEN NULL ELSE (subquery) END guard so all
+ * four functions return NULL when the input list is NULL.
+ *
+ * For all()/any()/none():
+ * SELECT CASE WHEN bool_or(pred IS TRUE/FALSE) THEN ...
+ * WHEN bool_or(pred IS NULL) THEN NULL
+ * ELSE ... END
+ * FROM unnest(list) AS x
+ *
Review Comment:
The PR description was updated to match the actual implementation — it now
explicitly describes the `bool_or()` aggregate + `CASE` shape and calls out
that this was chosen *rather than* EXISTS/NOT EXISTS, specifically to preserve
correct three-valued NULL handling (WHERE in a SQL subquery drops
NULL-producing rows, which would collapse `any(x IN [NULL] WHERE x > 0)` from
NULL to false under an EXISTS shape). No short-circuiting is claimed. See the
"SQL transformation strategy" section of the PR description.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
