Function AST_RewriteCallSubquery

src/ast/ast_rewrite_call_subquery.c:639–666

if the subquery will result in an eager and returning execution-plan rewrites it to contain the projections needed: 1. "n" -> "@n" in the initial WITH clause if exists. Otherwise, creates it. 2. "@n" -> "@n" in the intermediate WITH clauses. 3. "@n" -> "n" in the final RETURN clause. if the subquery will not result in an eager & returning execution-plan, does nothing

// if the subquery will not result in an eager & returning execution-plan, does
// nothing
bool AST_RewriteCallSubquery
(
	const cypher_astnode_t *root  // root of AST
) {
	if(cypher_astnode_type(root) != CYPHER_AST_STATEMENT) {
		return false;
	}

	// retrieve the root's body
	cypher_astnode_t *query =
		(cypher_astnode_t *)cypher_ast_statement_get_body(root);

	if(cypher_astnode_type(query) != CYPHER_AST_QUERY) {
		return false;
	}

	char **inter_names = array_new(char *, 0);
	bool rewritten = _rewrite_call_subquery_clauses(query, &inter_names);
	uint n_inter_names = array_len(inter_names);
	array_free_cb(inter_names, rm_free);

	// add a `WITH *` clause before every call {} clause
	// this is an optimization that decreases the mapping size of the plan up to
	// the CallSubquery operation
	rewritten |= _add_star_projections((cypher_astnode_t *)root);

	return rewritten;
}