v.21.1New Features
Provide SimpleState Combinator for AggregatingMergeTree in ClickHouse
Provide a new aggregator combinator :-SimpleStateto buildSimpleAggregateFunctiontypes via query. It's useful for defining MaterializedView of AggregatingMergeTree engine, and will benefit projections too. #16853 (Amos Bird).
Why it matters
This feature allows users to define Materialized Views using the AggregatingMergeTree engine more efficiently and enhances the capabilities of projections by enabling the construction of simple aggregate function states via queries.How to use it
Use the-SimpleState aggregator combinator in your aggregate function definitions within queries to create SimpleAggregateFunction states. This is particularly useful when defining Materialized Views on tables with the AggregatingMergeTree engine or when working with projections.