v.23.1New Feature

Array Join Support for Map Type in ClickHouse

Official CH changelog text
Array join support for the Map type, like the function "explode" in Spark. #43239 (李扬).
Added support for ARRAY JOIN with the Map type in ClickHouse, similar to the explode function in Spark.

Why it matters

This feature allows users to efficiently flatten Map type columns into multiple rows by expanding each key-value pair, enabling easier querying and analysis of map data structures.

How to use it

Use the ARRAY JOIN clause with a Map type column in your SELECT queries to expand map entries into separate rows.

Example:
SELECT key, value
FROM table
ARRAY JOIN map_column

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