Columnar OLAP Analytical Databases

Druid is a distributed columnar store and online analytical processing database designed for real-time analytics. It functions as a SQL analytics platform and a streaming data ingestion engine, allowing for the analysis of large datasets with low latency to support interactive dashboards and high-concurrency operational workloads. The system integrates a streaming data ingestion engine that loads information via batch or streaming processes to enable immediate analysis of arriving data. It provides high-performance analytical processing to execute slice-and-dice queries on massive data volumes for trend and pattern identification. The platform includes capabilities for distributed database management and cluster monitoring through SQL system tables. It supports data retrieval via standardized query languages and web-based application programming interfaces.

Doris is a distributed SQL data warehouse designed for high-performance analytical workloads and real-time data processing. It functions as a unified platform that integrates traditional relational warehousing with lakehouse query capabilities, allowing users to execute analytical operations directly against external data lakes without requiring data migration. The system distinguishes itself through a shared-nothing, massively parallel processing architecture that utilizes vectorized query execution and columnar storage to maintain sub-second latency. It supports dynamic schema evolution, enabling real-time updates to table structures, and provides elastic resource scaling by decoupling compute and storage layers to accommodate fluctuating workload demands. Beyond standard analytical processing, the platform incorporates vector database functionality to support artificial intelligence and semantic search applications. It enables hybrid search by combining structured SQL analytics with full-text filtering and vector similarity, facilitating complex retrieval-augmented generation workflows within a single environment. The engine is built to handle high-concurrency requirements, supporting thousands of simultaneous queries per second for enterprise-scale operations.

QuestDB is a high-performance, distributed time-series database designed for the ingestion, storage, and analysis of massive datasets. It functions as a real-time analytics platform that utilizes a columnar storage engine to optimize disk input and output, enabling efficient analytical scans and complex windowing operations on streaming data. The platform distinguishes itself through specialized capabilities for handling asynchronous time-series streams, including advanced join algorithms that align disparate data sets based on precise timestamp lookups. It supports high-volume ingestion through non-blocking data structures, allowing for simultaneous data entry and analytical querying without performance degradation. By decoupling compute from storage, the system enables independent scaling and utilizes shared object storage to maintain a consistent source of truth across distributed replicas. The system provides a comprehensive suite of tools for data lifecycle management, including automated partitioning, tiered storage, and incremental materialized views that update as new information arrives. It supports standard SQL for data exploration and offers granular security controls, including role-based access and encrypted communication, to ensure data governance. The platform is built to operate across diverse environments, ranging from on-premises setups to cloud-native deployments.

TDengine is a distributed time-series database designed for the high-speed ingestion, compression, and retrieval of timestamped metrics and sensor data. It functions as a SQL-compatible analytics engine, allowing users to perform complex operations on massive volumes of time-ordered information using standard relational syntax. The platform is built to serve as a backend foundation for industrial IoT environments, managing real-time data streams and device metadata through a cluster-based architecture. The system distinguishes itself through a distributed sharding architecture that uses consistent hashing to ensure horizontal scalability and high-throughput ingestion. It employs a log-structured write path to minimize disk seek latency and utilizes super-table virtualization to provide a unified logical view across multiple physical tables. To maintain performance and cost-efficiency, the database features automated multi-tiered lifecycle management, which migrates data between high-performance memory and low-cost storage based on age and access frequency. Beyond its core storage capabilities, the platform provides robust tools for edge-to-cloud synchronization, ensuring consistent data states across geographically distributed infrastructure. It includes built-in support for real-time stream processing, allowing for the analysis of live data without requiring external message queues. The system also incorporates comprehensive security frameworks, including user access control, audit logging, and encrypted transport protocols to protect sensitive operational data. Developers can interact with the database through native client libraries that support connection pooling and query parameter binding. The system is documented with comprehensive error code diagnostics and provides command-line utilities for cluster administration, health monitoring, and configuration management.

ClickHouse is a high-performance, columnar analytical database designed for real-time query execution and large-scale data aggregation. It functions as a distributed data warehouse capable of processing petabytes of information, while also providing an embedded engine that integrates directly into applications for native query capabilities without external dependencies. The system is built to handle high-throughput ingestion and complex analytical workloads, delivering millisecond-level latency for interactive dashboards and operational monitoring. The platform distinguishes itself through advanced storage and execution techniques, including vectorized query processing and a merge tree storage engine that maintains performance during massive insertions. It features adaptive subcolumn mapping for semi-structured data and supports native vector search for machine learning and generative AI applications. To facilitate efficient data movement, the engine utilizes zero-copy shared memory buffers, minimizing overhead when interacting with external analytical tools or processing diverse file formats like Parquet, JSON, and Arrow. Beyond its core storage and processing capabilities, the project provides a comprehensive suite of tools for observability, security, and data integration. It includes built-in support for natural language querying, automated workflow orchestration for AI agents, and extensive diagnostic features for query plan inspection. The platform also offers robust cloud infrastructure management, including support for private networking, compliant deployment strategies, and integrated billing consolidation.

DuckDB is an embedded, in-process analytical SQL database and OLAP database management system. It functions as a data engine for Parquet and CSV files, allowing users to execute complex SQL queries on large datasets without requiring a separate server process. The system is designed for local analytical processing and embedded data science workflows. It enables the direct querying and analysis of Parquet and CSV files from disk, bypassing the need to load data into a permanent database. The engine provides high-performance analytical SQL execution, including support for window functions and nested subqueries. It incorporates a columnar storage layout and vectorized query execution to handle large-scale data manipulation and exploration. The database is accessible via a standalone command line interface and language-specific bindings for Python, R, Java, and Wasm.

InfluxDB is a high-performance time-series database designed for collecting, storing, and querying time-stamped metrics and event data. It functions as a columnar time-series store and a real-time analytics engine, providing a network-accessible interface for retrieving and analyzing temporal records. The system utilizes a specialized columnar storage format to support high ingestion rates and efficient data retrieval. It incorporates a programmable runtime for executing custom plugins and triggers, including integration for processing and transforming incoming data streams. The platform covers wide-ranging capabilities for telemetry ingestion, operational metrics tracking, and real-time system monitoring. It supports temporal data analytics and uses standard SQL query languages to derive insights from continuous streams of event data.

DuckDB is an in-process analytical database engine designed to run directly within an application process. As a zero-dependency, embedded system, it provides enterprise-grade SQL data processing capabilities without the overhead of managing a dedicated database server. It is built to handle complex analytical and aggregation tasks by storing and retrieving information in columns, allowing for high-performance relational data manipulation. The engine distinguishes itself through a columnar vectorized execution model that maximizes CPU cache efficiency during query operations. It employs adaptive query optimization to dynamically select execution plans at runtime and utilizes zero-copy ingestion to map external data formats directly into memory. To facilitate integration with analytical programming environments, the system supports high-performance data exchange through standardized memory formats and provides specialized connectors for Python, R, and Java. The project covers a broad capability surface, including advanced relational join operations, incremental result streaming for large datasets, and flexible data ingestion from various file formats. It supports complex data types and provides a comprehensive command-line interface for interactive session management and batch processing. The codebase is designed for portability, offering single-file amalgamation to simplify integration into external projects and build systems.

This project is an open source relational database management system and SQL database designed for storing and managing structured data. It functions as a relational database for ensuring consistency and reliability, while also operating as a vector database for storing and querying high-dimensional vector embeddings. The system incorporates a columnar storage engine to optimize analytical query processing and large-scale data aggregation. It further enables vector similarity search, allowing users to find similar items by querying vector embeddings. The software covers a broad capability surface including relational data management, analytical query execution, and database telemetry collection for gathering hardware and configuration statistics.

Apache Druid is a real-time OLAP database and distributed analytics engine. It functions as a columnar time-series database designed for high-performance analytical queries and the real-time ingestion of streaming and batch datasets. The system provides a framework for high-concurrency analytics, allowing multiple simultaneous users to execute SQL and native queries across large-scale data. It supports mixed data ingestion, combining real-time streaming and batch loading into a single system for unified analysis. The platform includes capabilities for distributed cluster management, enabling the monitoring of data sources and system services through a centralized console.

InfluxDB is a specialized time series database platform engineered for the high-speed ingestion, compression, and retrieval of timestamped data at scale. It functions as a distributed metrics platform, providing the infrastructure necessary to organize and analyze massive volumes of time-stamped information to identify trends, patterns, and anomalies within complex data streams. The platform distinguishes itself through a functional dataflow engine that utilizes a specialized programming language for complex analytical transformations and automated tasks. This architecture is supported by a plugin-driven ingestion system that decouples data collection from core storage, alongside a distributed consensus protocol that ensures high availability and metadata consistency across clustered environments. To maintain performance as data grows, the system employs shard-based partitioning, columnar compression, and log-structured merge-tree storage to optimize write throughput and analytical query execution. Beyond core storage, the platform provides a comprehensive suite of tools for infrastructure monitoring, automated alerting, and data visualization. Users can manage the entire data lifecycle through a centralized control plane that handles cluster provisioning, security, and retention policies. The ecosystem includes integrated agent management for telemetry collection, allowing for consistent configuration and health monitoring across distributed computing environments. Deployment options are flexible, ranging from single-node instances for development to fully-managed cloud, serverless, and enterprise-grade clustered services.

TiDB is a horizontally scalable, distributed SQL database designed to provide consistent transactional storage and high-performance analytical processing within a single unified architecture. It utilizes a decoupled compute-storage design and a distributed key-value storage layer to ensure horizontal scalability and efficient range-based queries. By employing a consensus-based replication algorithm, the system maintains high availability and automatic failover across multiple nodes and geographical regions. The platform distinguishes itself through its hybrid transactional and analytical processing capabilities, which allow complex SQL queries to run against replicated columnar data without disrupting primary transactional workloads. It also integrates high-dimensional vector search functionality, enabling semantic similarity queries directly alongside traditional relational data. To support diverse operational needs, the system provides native tools for real-time data streaming, seamless migration from external database systems, and multi-region disaster recovery. The database is built for cloud-native environments, offering comprehensive lifecycle management through Kubernetes operators that automate deployment, scaling, and rolling upgrades. It maintains compatibility with standard SQL interfaces, allowing applications to connect using common drivers while managing complex concurrency through pessimistic transaction handling. Detailed documentation and command-line utilities are available to assist with cluster orchestration, performance troubleshooting, and the configuration of production-grade topologies.

Citus is a PostgreSQL extension that transforms a standard database into a distributed system. It functions as a sharding framework and distributed SQL engine, enabling horizontal scaling by partitioning tables across a cluster of nodes. By utilizing a coordinator-worker topology, the system manages metadata and routes queries to the appropriate nodes, allowing for parallel execution of complex operations across distributed data shards. The platform distinguishes itself through its specialized support for multi-tenant architectures and real-time analytical processing. It enables tenant-based distribution and schema-based sharding, which allows for the isolation of tenant data and the migration of high-volume workloads to dedicated nodes. To accelerate analytical performance, the system integrates columnar storage with data compression and supports pre-aggregated rollups, ensuring that large-scale datasets remain performant as the cluster grows. Beyond its core distribution capabilities, the project provides comprehensive tools for cluster administration and data lifecycle management. It automates shard rebalancing, schema propagation via a two-phase commit protocol, and the maintenance of time-based partitions. The system also includes diagnostic utilities for monitoring query performance, detecting resource contention, and analyzing index usage across the distributed environment.

OceanBase is a distributed SQL database designed for high availability and strong consistency across multiple nodes and regions. It functions as a hybrid transactional and analytical processing engine, allowing real-time analytics and transactions to execute on a single data copy. The system also serves as a vector database engine for indexing and querying vector data to power semantic search and recommendation systems. The platform features native compatibility layers for MySQL and Oracle, enabling the migration of legacy workloads without rewriting SQL code. It utilizes a Paxos-based distributed store for synchronous replication and implements a multi-tenant architecture that isolates CPU, memory, and I/O resources for different tenants within a single cluster. The system covers a broad range of capabilities, including horizontal storage scaling, distributed transaction management, and hybrid row-columnar storage. It provides tools for cluster orchestration, automated load balancing via log-stream migration, and disaster resilience through multi-zone replication and automated failover. Deployment and management are supported through a Kubernetes operator and a web monitoring dashboard.

Dgraph is a distributed graph database designed to store and query highly connected data. It organizes information as nodes and edges to represent complex relationships between entities, providing a platform for managing and analyzing deeply linked datasets. The system functions as a horizontally scalable cluster that partitions data across multiple nodes to maintain performance and availability as information volume increases. It utilizes a specialized query language built for low-latency navigation of interconnected data points, allowing for the execution of complex queries across large-scale information networks. The platform incorporates a graph-oriented storage engine and in-memory indexing to facilitate efficient traversal of relationships. It manages state changes and data consistency through a distributed consensus algorithm and predicate-based sharding, which enables the system to decompose and execute queries in parallel across the cluster.

RisingWave is a cloud-native streaming database and real-time analytics engine that uses standard SQL to process continuous data streams. It functions as a streaming data lakehouse, combining the capabilities of a streaming SQL database with a platform that integrates streaming ingestion with open table formats. The system is distinguished by its use of the PostgreSQL wire protocol, allowing it to integrate with existing SQL tools and drivers. It employs a decoupled compute and storage architecture, persisting streaming state and materialized views in cloud object storage to enable independent scaling and rapid recovery. The platform covers a broad range of real-time data operations, including change data capture, streaming ETL pipelines, and the maintenance of incremental materialized views. It supports complex stream processing such as windowed aggregations, event-time tracking with watermarks, and the continuous export of processed data to downstream sinks. The project can be deployed via Kubernetes and Helm, Docker Compose, or as a managed instance.

GreptimeDB is a distributed, open-source time-series database built for unified observability. It stores and queries metrics, logs, and traces together in a single columnar engine, supporting both SQL and PromQL for analysis. The database is designed as a Kubernetes-native operator with a decoupled compute and storage architecture, enabling horizontal scaling and multi-region deployment. What distinguishes GreptimeDB is its role as a multi-protocol ingestion gateway, accepting data through OpenTelemetry, Prometheus Remote Write, InfluxDB, Loki, Elasticsearch, Kafka, and MQTT protocols without requiring a predefined schema. It provides a unified observability data model that processes all three signal types as timestamped wide events, allowing JOIN queries across signals. The system includes a continuous aggregation pipeline with an optional Flownode component for streaming and materialized view computations, plus configurable log pipeline processing that parses and transforms raw log lines during ingestion. The database offers a broad capability surface including automatic schema inference, columnar storage with LSMT, distributed query execution with pushdown, and support for inverted, fulltext, and skipping indexes. It provides multiple query APIs (MySQL, PostgreSQL, HTTP, gRPC, Elasticsearch, Jaeger), BI tool connectivity, and integration with AI assistants through the Model Context Protocol. Deployment options range from standalone binaries to distributed clusters on Kubernetes, with metadata stored in etcd, MySQL, or PostgreSQL.

Apache IoTDB is a time-series database designed for the Internet of Things, purpose-built to ingest high-volume data from millions of low-power devices and store timestamp-value pairs with configurable data types and encoding schemes. It organizes time series data and device metadata in a tree-like hierarchy, enabling efficient management of complex industrial sensor networks. The database supports rich querying capabilities, including time-aligned data retrieval across multiple devices, time-based aggregation like downsampling, and frequency-domain signal analysis. It provides high-throughput read and write operations while compressing stored data with high-ratio algorithms to reduce hardware storage costs. Data can be imported from and exported to external files for backup or transfer. IoTDB integrates with big data ecosystems such as Hadoop, Spark, Flink, and Grafana for processing, analysis, and visualization. It offers flexible deployment options across edge and cloud environments with one-click setup and data synchronization between nodes.