Function _ValidateUnion_Clauses

src/ast/ast_validations.c:990–1081

validate UNION clauses

// validate UNION clauses
static AST_Validation _ValidateUnion_Clauses
(
	const AST *ast  // ast-node
) {
	AST_Validation res = AST_VALID;

	uint *union_indices = AST_GetClauseIndices(ast, CYPHER_AST_UNION);
	uint union_clause_count = array_len(union_indices);
	array_free(union_indices);

	if(union_clause_count != 0) {
		// Require all RETURN clauses to perform the exact same projection
		uint *return_indices = AST_GetClauseIndices(ast, CYPHER_AST_RETURN);
		uint return_clause_count = array_len(return_indices);

		// We should have one more RETURN clauses than we have UNION clauses.
		if(return_clause_count != union_clause_count + 1) {
			ErrorCtx_SetError("Found %d UNION clauses but only %d RETURN clauses.", union_clause_count,
							return_clause_count);
			array_free(return_indices);
			return AST_INVALID;
		}

		const cypher_astnode_t *return_clause = cypher_ast_query_get_clause(ast->root, return_indices[0]);
		uint proj_count = cypher_ast_return_nprojections(return_clause);
		const char *projections[proj_count];

		for(uint j = 0; j < proj_count; j++) {
			const cypher_astnode_t *proj = cypher_ast_return_get_projection(return_clause, j);
			const cypher_astnode_t *alias_node = cypher_ast_projection_get_alias(proj);
			if(alias_node == NULL)  {
				// The projection was not aliased, so the projection itself must be an identifier.
				alias_node = cypher_ast_projection_get_expression(proj);
				ASSERT(cypher_astnode_type(alias_node) == CYPHER_AST_IDENTIFIER);
			}
			const char *alias = cypher_ast_identifier_get_name(alias_node);
			projections[j] = alias;
		}

		for(uint i = 1; i < return_clause_count; i++) {
			return_clause = cypher_ast_query_get_clause(ast->root, return_indices[i]);
			if(proj_count != cypher_ast_return_nprojections(return_clause)) {
				ErrorCtx_SetError("All sub queries in a UNION must have the same column names.");
				res = AST_INVALID;
				goto cleanup;
			}

			for(uint j = 0; j < proj_count; j++) {
				const cypher_astnode_t *proj = cypher_ast_return_get_projection(return_clause, j);
				const cypher_astnode_t *alias_node = cypher_ast_projection_get_alias(proj);
				if(alias_node == NULL)  {
					// The projection was not aliased, so the projection itself must be an identifier.
					alias_node = cypher_ast_projection_get_expression(proj);
					ASSERT(cypher_astnode_type(alias_node) == CYPHER_AST_IDENTIFIER);
				}
				const char *alias = cypher_ast_identifier_get_name(alias_node);
				if(strcmp(projections[j], alias) != 0) {
					ErrorCtx_SetError("All sub queries in a UNION must have the same column names.");