317brian commented on code in PR #16704: URL: https://github.com/apache/druid/pull/16704#discussion_r1683713056
########## docs/release-info/migr-ansi-sql-null.md: ########## @@ -0,0 +1,386 @@ +--- +id: migr-ansi-sql-null +title: "Migration guide: SQL compliant mode" +sidebar_label: SQL compliant mode +--- + +<!-- + ~ 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. +--> +import Tabs from '@theme/Tabs'; +import TabItem from '@theme/TabItem'; + +In Apache Druid 28.0.0, the default [null handling](../querying/sql-data-types.md#null-values) mode changed to be compliant with the ANSI SQL standard. +This guide provides strategies for Druid operators who rely on legacy Druid null handling behavior in their applications to transition to SQL compliant mode. +Legacy mode is planned for removal from Druid. + +## SQL compliant null handling + +As of Druid 28.0.0, Druid writes segments in a SQL compatible null handling mode by default. +This means that Druid stores null values distinctly from empty strings for string dimensions and distinctly from 0 for numeric dimensions. + +This can impact your application behavior because the ANSI SQL standard defines any comparison to null to be unknown. +According to this three-valued logic, `x <> 'some value'` only returns non-null values. + +The default Druid configurations for 28.0.0 and later that enable SQL compatible null handling mode are the following: Review Comment: ```suggestion The default Druid configurations for 28.0.0 and later that enable ANSI SQL compatible null handling mode are the following: ``` -- 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]
