Function _Validate_reduce

src/ast/ast_validations.c:606–711

validate reduce

// validate reduce
static VISITOR_STRATEGY _Validate_reduce
(
	const cypher_astnode_t *n,  // ast-node
	bool start,                 // first traversal
	ast_visitor *visitor        // visitor
) {
	validations_ctx *vctx = AST_Visitor_GetContext(visitor);
	if(!start) {
		return VISITOR_CONTINUE;
	}

	cypher_astnode_type_t orig_clause = vctx->clause;
	// change clause type of vctx so that function-validation will work properly
	// (include-aggregations should be set to false)
	vctx->clause = CYPHER_AST_REDUCE;

	// A reduce call has an accumulator and a local list variable that should
	// only be accessed within its scope;
	// do not leave them in the identifiers map
	// example: reduce(sum=0, n in [1,2] | sum+n)
	//  the reduce function is composed of 5 components:
	//     1. accumulator                  `sum`
	//     2. accumulator init expression  `0`
	//     3. list expression              `[1,2,3]`
	//     4. variable                     `n`
	//     5. eval expression              `sum + n`
	
	// make sure that the init expression is a known var or valid exp.
	const cypher_astnode_t *init_node = cypher_ast_reduce_get_init(n);
	if(cypher_astnode_type(init_node) == CYPHER_AST_IDENTIFIER) {
		// check if the variable has already been introduced
		const char *var_str = cypher_ast_identifier_get_name(init_node);
		if(raxFind(vctx->defined_identifiers, (unsigned char *)var_str, strlen(var_str)) == raxNotFound) {
			ErrorCtx_SetError("%s not defined.", var_str);
			return VISITOR_BREAK;
		}
	}
	else {
		AST_Visitor_visit(init_node, visitor);
		if(ErrorCtx_EncounteredError()) {
			return VISITOR_BREAK;
		}
	}

	// make sure that the list expression is a list (or list comprehension) or an 
	// alias of an existing one.
	const cypher_astnode_t *list_var = cypher_ast_reduce_get_expression(n);
	if(cypher_astnode_type(list_var) == CYPHER_AST_IDENTIFIER) {
		const char *list_var_str = cypher_ast_identifier_get_name(list_var);
		if(raxFind(vctx->defined_identifiers, (unsigned char *) list_var_str, strlen(list_var_str)) == raxNotFound) {
			ErrorCtx_SetError("%s not defined", list_var_str);
			return VISITOR_BREAK;
		}
	}

	// Visit the list expression (no need to introduce local vars)
	AST_Visitor_visit(list_var, visitor);
	if(ErrorCtx_EncounteredError()) {