Function _ValidateQueryTermination

src/ast/ast_validations.c:1812–1884

A query must end in a RETURN clause, a procedure, or an updating clause (CREATE, MERGE, DELETE, SET, REMOVE, FOREACH or CALL {})

// A query must end in a RETURN clause, a procedure, or an updating clause
// (CREATE, MERGE, DELETE, SET, REMOVE, FOREACH or CALL {})
static AST_Validation _ValidateQueryTermination
(
	const AST *ast  // ast
) {
	ASSERT(ast != NULL);

	const cypher_astnode_t *root = ast->root;
	uint clause_idx = 0;
	const cypher_astnode_t *return_clause = NULL;
	const cypher_astnode_t *following_clause = NULL;
	uint clause_count = cypher_ast_query_nclauses(root);

	const cypher_astnode_t *last_clause = cypher_ast_query_get_clause(root,
		clause_count - 1);
	cypher_astnode_type_t type = cypher_astnode_type(last_clause);
	if(type != CYPHER_AST_RETURN         &&
	   type != CYPHER_AST_CREATE         &&
	   type != CYPHER_AST_MERGE          &&
	   type != CYPHER_AST_DELETE         &&
	   type != CYPHER_AST_SET            &&
	   type != CYPHER_AST_CALL           &&
	   type != CYPHER_AST_CALL_SUBQUERY  &&
	   type != CYPHER_AST_REMOVE         &&
	   type != CYPHER_AST_FOREACH
	  ) {
			ErrorCtx_SetError("Query cannot conclude with %s (must be a RETURN \
clause, an update clause, a procedure call or a non-returning subquery)",
						cypher_astnode_typestr(type));
		return AST_INVALID;
	}

	// if the last clause is CALL {}, it must be non-returning
	if(type == CYPHER_AST_CALL_SUBQUERY) {
		cypher_astnode_t *query =
			cypher_ast_call_subquery_get_query(last_clause);
		if(cypher_astnode_type(cypher_ast_query_get_clause(query,
				cypher_ast_query_nclauses(query)-1)) ==
		   CYPHER_AST_RETURN) {
			ErrorCtx_SetError("A query cannot conclude with a returning \
subquery (must be a RETURN clause, an update clause, a procedure call or a \
non-returning subquery)");

			return AST_INVALID;
		}
	}

	// validate that `UNION` is the only clause following a `RETURN` clause, and
	// termination of embedded call {} clauses
	bool last_was_return = false;
	for(uint i = 0; i < clause_count; i++) {
		const cypher_astnode_t *clause = cypher_ast_query_get_clause(root, i);
		cypher_astnode_type_t type = cypher_astnode_type(clause);
		if(type != CYPHER_AST_UNION && last_was_return) {
			// unexpected clause following RETURN
			ErrorCtx_SetError("Unexpected clause following RETURN");
			return AST_INVALID;
		} else if(type == CYPHER_AST_RETURN) {
			last_was_return = true;