danielcweeks commented on code in PR #16652: URL: https://github.com/apache/iceberg/pull/16652#discussion_r3351444568
########## format/expressions-spec.md: ########## @@ -0,0 +1,284 @@ +--- +title: "Expressions Spec" +--- +<!-- + - Licensed to the Apache Software Foundation (ASF) under one or more + - contributor license agreements. See the NOTICE file distributed with + - this work for additional information regarding copyright ownership. + - The ASF licenses this file to You under the Apache License, Version 2.0 + - (the "License"); you may not use this file except in compliance with + - the License. You may obtain a copy of the License at + - + - http://www.apache.org/licenses/LICENSE-2.0 + - + - Unless required by applicable law or agreed to in writing, software + - distributed under the License is distributed on an "AS IS" BASIS, + - WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + - See the License for the specific language governing permissions and + - limitations under the License. + --> + +# Iceberg Expressions + +This document defines the structure and behavior of expressions for use in Iceberg specifications. The purpose is to define a common structure that enables simple expressions to be stored and exchanged. + +Stored expressions are needed for use cases like data validations (`CHECK` constraints) and default values (for instance, `current_timestamp()`). Expressions are exchanged in use cases like server-side scan planning in the catalog protocol. + + +## Overview + +The goal of this specification is to define a simple expression structure and avoid complexity. + +To remain simple, the expressions that can be represented are deliberately constrained. Value expressions are constants, field references, or function calls with value expression arguments. Predicates are comparisons of value expressions that produce true or false. Review Comment: ```suggestion To remain simple, the expressions that can be represented are deliberately constrained. - Value expressions: constants, field references, or function calls with value expression arguments. - Predicates: comparisons of value expressions that produce true or false. ``` I think bulleting here would help emphasize the two types/categories -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
