luoyuxia commented on code in PR #20696: URL: https://github.com/apache/flink/pull/20696#discussion_r964462819
########## docs/content/docs/dev/table/hiveCompatibility/hiveDialect/overview.md: ########## @@ -0,0 +1,97 @@ +--- +title: "Overview" +weight: 1 +type: docs +aliases: +- /dev/table/hiveCompatibility/hiveDialect/overview +--- +<!-- +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. +--> + +# Hive Dialect + +Flink allows users to write SQL statements in Hive syntax when Hive dialect is used. +By providing compatibility with Hive syntax, we aim to improve the interoperability with Hive and reduce the scenarios when users need to switch between Flink and Hive in order to execute different statements. + +## Use Hive Dialect + +Flink currently supports two SQL dialects: `default` and `hive`. You need to switch to Hive dialect +before you can write in Hive syntax. The following describes how to set dialect with +SQL Client and Table API. Also notice that you can dynamically switch dialect for each +statement you execute. There's no need to restart a session to use a different dialect. + +{{< hint warning >}} +**Note:** + +- To use Hive dialect, you have to add dependencies related to Hive. Please refer to [Hive dependencies]({{< ref "docs/connectors/table/hive/overview" >}}#dependencies) for how to add the dependencies. +- Please make sure the current catalog is [HiveCatalog]({{< ref "docs/connectors/table/hive/hive_catalog" >}}). Otherwise, it will fall back to Flink's `default` dialect. +- In order to have better syntax and semantic compatibility, it’s highly recommended to load [HiveModule]({{< ref "docs/connectors/table/hive/hive_functions" >}}#use-hive-built-in-functions-via-hivemodule) and + place it first in the module list, so that Hive built-in functions can be picked up during function resolution. + Please refer [here]({{< ref "docs/dev/table/modules" >}}#how-to-load-unload-use-and-list-modules) for how to change resolution order. +- Hive dialect only supports 2-part identifiers, so you can't specify catalog for an identifier. +- While all Hive versions support the same syntax, whether a specific feature is available still depends on the + [Hive version]({{< ref "docs/connectors/table/hive/overview" >}}#supported-hive-versions) you use. For example, updating database + location is only supported in Hive-2.4.0 or later. +{{< /hint >}} + +### SQL Client + +SQL dialect can be specified via the `table.sql-dialect` property. +Therefore，you can set the dialect after the SQL Client has launched. + +```bash +Flink SQL> SET 'table.sql-dialect' = 'hive'; -- to use hive dialect +[INFO] Session property has been set. + +Flink SQL> SET 'table.sql-dialect' = 'default'; -- to use default dialect Review Comment: I perfer not. In hive's way, `SET 'key' = 'value'` is different from `SET key = value`. -- 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]
