Clickhouse vs TiDB: What are the differences?

Introduction

Here we will discuss the key differences between ClickHouse and TiDB.

1. Data Model: ClickHouse uses a columnar data model, which means that data is stored and processed column by column. On the other hand, TiDB uses a row-based data model, where data is stored and processed row by row. This difference in data model can impact the performance and efficiency of query processing.

2. Distributed Architecture: ClickHouse is designed to be a distributed system by default, allowing for horizontal scaling and high availability. In contrast, TiDB is a distributed NewSQL database that combines the scalability of NoSQL with the ACID guarantees of SQL databases. Its distributed architecture enables automatic data sharding and efficient load balancing.

3. Consistency Model: ClickHouse provides eventual consistency, which means that updates to the data might not be immediately visible to all the nodes in the cluster. TiDB, on the other hand, provides strong consistency, ensuring that updates are immediately visible and that concurrent transactions do not result in conflicts.

4. SQL Compatibility: Although both ClickHouse and TiDB support SQL, they have differences in SQL compatibility. ClickHouse supports a subset of SQL, focusing on analytical workloads. TiDB, being a NewSQL database, aims to provide full SQL compatibility with features such as joins, indexes, and transactions.

5. Replication Mechanism: ClickHouse uses a log-based replication mechanism, where log files are replicated between nodes. This approach allows for efficient replication and can handle high write throughput. TiDB, on the other hand, uses a Raft-based consensus protocol for replication, ensuring data consistency across nodes in the cluster.

6. Storage Engine: ClickHouse uses its own storage engine optimized for columnar data processing, which provides high compression and fast query execution for analytical workloads. TiDB, on the other hand, uses a pluggable storage engine architecture and supports multiple engines like TiKV and TiFlash, providing flexibility for different use cases.

In summary, ClickHouse and TiDB differ in their data model, distributed architecture, consistency model, SQL compatibility, replication mechanism, and storage engine, making them suitable for different use cases and performance requirements.