ektravel commented on code in PR #16516: URL: https://github.com/apache/druid/pull/16516#discussion_r1635425149
########## docs/release-info/migr-mvd-array.md: ########## @@ -0,0 +1,245 @@ +--- +id: migr-mvd-array +title: "Migration guide: MVDs to arrays" +sidebar_label: MVDs to arrays +--- + +<!-- + ~ 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. +--> + + +Druid now supports SQL-compliant [arrays](../querying/arrays.md), and we recommend that people use arrays over [multi-value dimensions](../querying/multi-value-dimensions.md) (MVDs) whenever possible. +Use arrays for new projects and complex use cases involving multiple data types. Use MVDs for specific use cases, such as operating directly on individual elements like regular strings. If your operations involve complete arrays of values, including the ordering of values within a row, use arrays over MVDs. + +## Comparison between arrays and MVDs + +The following table compares the general behavior between arrays and MVDs. +For specific query differences between arrays and MVDs, see [Querying arrays and MVDs](#querying-arrays-and-mvds). + +| | Arrays| Multi-value dimensions (MVDs) | +|---|---|---| +| Data types | Supports VARCHAR, BIGINT, and DOUBLE types (ARRAY<STRING\>, ARRAY<LONG\>, ARRAY<DOUBLE\>) | Only supports arrays of strings (VARCHAR) | +| SQL compliance | Behaves like standard SQL arrays with SQL-compliant behavior | Behaves like SQL VARCHAR rather than standard SQL arrays and requires special SQL functions to achieve array-like behavior. See the [examples](#examples). | +| Ingestion | <ul><li>JSON arrays are ingested as Druid arrays</li><li>Managed through the query context parameter `arrayIngestMode` in SQL-based ingestion (supported options: `array`, `mvd`, `none`). Note that if you set this mode to `none`, Druid raises an exception if you try to store any type of array.</li></ul> | <ul><li>JSON arrays are ingested as multi-value dimensions</li><li>Managed using functions like [ARRAY_TO_MV](../querying/sql-functions.md#array_to_mv) in SQL-based ingestion</li></ul> | Review Comment: ```suggestion | Ingestion | <ul><li>JSON arrays are ingested as Druid arrays</li><li>Managed through the query context parameter `arrayIngestMode` in SQL-based ingestion. Supported options are `array`, `mvd`, and `none`. Note that if you set this mode to `none`, Druid raises an exception if you try to store any type of array.</li></ul> | <ul><li>JSON arrays are ingested as MVDs</li><li>Managed using functions like [ARRAY_TO_MV](../querying/sql-functions.md#array_to_mv) in SQL-based ingestion</li></ul> | ``` -- 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: commits-unsubscr...@druid.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@druid.apache.org For additional commands, e-mail: commits-h...@druid.apache.org
