courtesy of Jeremy Nguyen
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ВсеПрибалтикаУкраинаБелоруссияМолдавияЗакавказьеСредняя Азия
The cost of groceries soared following Russia's invasion of Ukraine, which pushed up energy prices. Own-brand products, which make up most of the goods on Aldi and Lidl shelves, now make up more than half of everything shoppers buy, by value.
We also see even experienced users being caught by less obvious LIMIT behavior in multi-node environments where a table has many shards. Sharding allows users to split or replicate their data across multiple instances of ClickHouse. When a query with a LIMIT N clause is sent to a sharded table e.g. via a distributed table, this clause will be propagated down to each shard. Each shard will, in turn, need to collate the top N results, returning them to the coordinating node. This can prove particularly resource-intensive when users run queries that require a full table scan. Typically these are "point lookups" where the query aims to just identify a few rows. While this can be achieved in ClickHouse with careful index design a non-optimized variant, coupled with a LIMIT clause, can prove extremely resource-intensive.