Time-series data is emerging as the dominant type of data produced in IoT, Financial Services, Manufacturing, DevOps, monitoring, machine learning, and AI. Time series databases are specialized for storing and analyzing this kind of data efficiently and quickly. This article compares QuestDB with InfluxDB to help understand the key differences so you can choose a time series database that fits your use case.
The typical uses of time series databases are for:
- Application performance, uptime, and response times
- Analyzing financial transactions and trades
- Monitoring network logs
- Asset tracking
- E-commerce transaction data, sales insights, BI reports
- Sensor data from IoT devices
While the traditional use of databases was to store the last-known state of a system, this only shows a snapshot of a point in time. In contrast, time series data adds a historical dimension to help understand how information changes.
Understanding how information changes over time help make predictions about your data, gain deeper insights into trends, and be better prepared for future variations. For this reason, developers need a time-series database that's robust, easy to use, and powerful. Importantly, it must be flexible enough to be used across different scenarios, industries, and use cases.
One of the first places to begin comparing QuestDB and InfluxDB is how data is handled and stored in each database. InfluxDB has a dedicated line protocol message format for ingesting measurements. Each measurement has a timestamp, a set of tags (a tagset), and a set of fields (a fieldset).
In InfluxDB, tagset values are strings and are indexed, while fieldset values are not indexed. The data types that fields may use are limited to floats, ints, strings, and booleans. The following snippet is an example message in InfluxDB line protocol for illustration:
QuestDB supports InfluxDB line protocol for compatibility purposes, so inserts using InfluxDB line protocol match the data types available. QuestDB supports additional numeric types, such as bytes for 8-bit integers, shorts for 16-bit integers, float for 32-bit floats, and long256 for larger integers. Additional types can be used while ingesting InfluxDB line protocol by creating a table with a desired schema before starting to write data.
QuestDB also exposes PostgreSQL wire protocol and a REST API for inserts, allowing for more control over the data types that the system can handle, including additional types such as date, char, and binary. In QuestDB, it's also possible to add indexes and to existing columns in tables, which can be done directly through SQL:
QuestDB has full support for relational queries, whereas InfluxDB is a NoSQL, non-relational database with a custom data model. QuestDB supports both schema-agnostic ingestion over InfluxDB line protocol and a relational data model. Users can leverage both paradigms and perform SQL JOINs to correlate "schemaless" data with relational data by timestamp.
For storage, InfluxDB uses Time-Structured Merge Trees (TSM) where data is stored in a columnar format, and the storage engine stores differences (or deltas) between values in a series. For indexing, InfluxDB uses a Time Series Index intended to keep queries fast as cardinality grows. Still, the efficiency of this index has its limitations, explored in more detail in the High-Cardinality section below.
QuestDB also uses columnar data structures but indexes data in vector-based append-only column files. As of QuestDB version 6.0, sorting out-of-order data occurs in a staging area in-memory, merging sorted and persisted data at commit time using an append model. The reason for sorting in-memory and merging with persisted data in this way is to keep the storage engine performant on both read and write operations.
InfluxDB has a shard group concept as a strategy for partitioning, which allows for grouping data by time. Users can provide a shard group duration which defines how large a shard will be and can enable common operations such as retention periods for data (deleting data older than X days, for example):
QuestDB has similar functionality to partition tables by time, and users may specify a partition size for tables based on days, months, or years. When tables are partitioned by time, table metadata table is defined once per table, and column files are partitioned at the filesystem level into directories per partition:
Both QuestDB and InfluxDB have ways to partition data by time and employ a retention strategy. The difference in partitioning for each system is the broader terminology, and the fact that QuestDB does not need to create separate TSM files on disk per partition.
The emergence of NoSQL as a popular paradigm has effectively split databases into two categories: SQL and NoSQL. InfluxDB originally started with a language similar to SQL called InfluxQL, which balanced some aspects of SQL with custom syntax. InfluxDB eventually adopted Flux as a query language to interact with data.
QuestDB embraces SQL as the primary query language so that there is no need for learning custom query languages. SQL is a good choice for time-series databases; it's easy to understand, most developers are familiar with it already, and SQL skills are simple to apply across different systems. As reported by the Stack Overflow developer survey of 2020, it's the third most popular language used by developers. It proves to be a long-standing choice for quickly asking questions about the characteristics of your data.
Flux enables you to work with InfluxDB more efficiently, but it's difficult to read, and it's harder to learn and onboard new users. From users' perspective, learning a new custom query language is inconvenient for accessibility regardless of their engineering background.
Consider that the Flux query above can be written in SQL as follows:
Users who have no developer background will have a barrier of entry, making it difficult to use standard BI tools to gain insights on time series data. SQL is a time-tested language that those without engineering backgrounds can pick up quickly.
Let's compare how QuestDB and InfluxDB operate in terms of performance. The Time Series Benchmark Suite (TSBS) regularly appears in discussions about database performance. The TSBS is a collection of Go programs to generate datasets and then benchmark read and write performance. The suite is extensible so that different use cases and query types can be included and compared across systems. To generate data for these benchmarks, commands look like the following:
The data produced from
tsbs_generate_data above has the following features:
- 4000 unique devices (scale)
- 500MB data set
- 24 hours worth of simulated data
- InfluxDB line protocol
This is an example of the first few lines from the generated data set:
QuestDB reaches maximum ingestion performance using four threads, whereas InfluxDB requires more workers to hit maximum throughput. QuestDB achieves 959k rows/sec with four threads, whereas InfluxDB needs 14 threads to reach its max ingestion rate (334k rows/sec).
Cardinality typically refers to the number of elements in a set's size. In the context of a time series database (TSDB), high-cardinality boils down to many indexed columns in a table and each indexed column containing many unique values.
High-cardinality is a known problem area for InfluxDB, and this is likely because of the system architecture and storage engine. InfluxDB uses data structures based on LSM-trees which are known to perform poorly in high-cardinality scenarios. In QuestDB, the storage model is radically different from LSM trees or B-trees and instead uses data stored in densely ordered vectors on disk.
We ran the TSBS benchmark specifying different scale values for multiple data sets and tested ingestion using up to sixteen threads to determine the maximum throughput of each system and to get an idea of how ingestion rates change over time:
With low cardinality data sets, QuestDB hits maximum ingestion throughput of 904k rows/sec, and at 10 million unique devices, QuestDB sustains 640k rows/sec. InfluxDB ingestion starts at 220k rows/sec on 100 devices and reached 38k rows/sec on the 10M device dataset.
As we ran high-cardinality data sets, InfluxDB struggled to keep up with inserts. The bottleneck is likely due to the use of Time-Structured Merge Trees. The issues manifested at first in degraded ingestion rates, but eventually, out-of-memory errors begin to appear at runtime. We provided more workers to the systems under test to investigate if adding more threads would offer more stability, however InfluxDB was unable to finish the tests with 10M devices:
InfluxDB requires a lot more threads to be able to handle high-cardinality data, but there are diminishing returns on adding more workers, revealing that there are underlying barriers which are not overcome by providing more threads to the system.
QuestDB handles high-cardinality better with more threads. When cardinality is low, fewer workers lead to an overall higher maximum throughput, but a steeper drop in ingestion rates when going from 1M devices to 10M.
The community is vital to QuestDB so that beginners have an environment that encourages getting up and running quickly. Experienced users have channels for raising technical questions or bugs with the engineering team or other power users. We have a growing Slack workspace with over 900 members who discuss how they are using QuestDB daily to power their businesses. Our mission is to solve the problems users have with time series data. To achieve that, we are driven to understand the pain points that arise from practical scenarios, and we have the community as a force that informs our product roadmap.
We designed QuestDB to sidestep custom query languages that require specialist knowledge to understand. We believe that it should be easy to ask questions about how your own data looks and changes. Support, community forums, and online resources are a treasure trove of many decades of knowledge working with SQL which directly transfers to using QuestDB. If you are new to QuestDB (or SQL), it's easy to get started by means of online resources, tutorials, and the expertise shared by our community. For seasoned SQL experts, there is no learning curve except for time-based calculations and analysis specific for time series.
We want to make sure engineers can pick the right tool for the job and have highlighted some key differentiators between QuestDB and InfluxDB. If there are suggestions for improving this comparison, we'd be happy to include this in our analysis.