Function _ValidateMergeRelation

src/ast/ast_validations.c:215–249

Verify that MERGE doesn't redeclare bound relations, that one reltype is specified for unbound relations, and that the entity is not a variable length pattern

// Verify that MERGE doesn't redeclare bound relations, that one reltype is specified for unbound relations, 
// and that the entity is not a variable length pattern
static AST_Validation _ValidateMergeRelation
(
	const cypher_astnode_t *entity,  // ast-node (rel-pattern)
	rax *defined_aliases             // bound variables
) {
	// Verify that this is not a variable length relationship
	const cypher_astnode_t *range = cypher_ast_rel_pattern_get_varlength(entity);
	if(range) {
		ErrorCtx_SetError("Variable length relationships cannot be used in MERGE");
		return AST_INVALID;
	}

	const cypher_astnode_t *identifier = cypher_ast_rel_pattern_get_identifier(entity);
	const char *alias = NULL;
	if(identifier) {
		alias = cypher_ast_identifier_get_name(identifier);
		// Verify that we're not redeclaring a bound variable
		if(raxFind(defined_aliases, (unsigned char *)alias, strlen(alias)) != raxNotFound) {
			ErrorCtx_SetError("The bound variable %s' can't be redeclared in a MERGE clause", alias);
			return AST_INVALID;
		}
	}

	// Exactly one reltype should be specified for the introduced edge
	uint reltype_count = cypher_ast_rel_pattern_nreltypes(entity);
	if(reltype_count != 1) {
		ErrorCtx_SetError("Exactly one relationship type must be specified for each relation in a MERGE pattern.");
		return AST_INVALID;
	}

	// We don't need to validate the MERGE edge's direction, as an undirected edge
	// in MERGE should result a single outgoing edge to be created.

	return AST_VALID;
}

// Verify that MERGE does not introduce labels or properties to bound nodes
static AST_Validation _ValidateMergeNode