Grafana

Grafana is a popular observability and monitoring application used to visualize data and has an extensive ecosystem of widgets and plugins. QuestDB supports connecting to Grafana via the Postgres endpoint. There's also a complete tutorial that shows you how to use QuestDB with Grafana step by step.

Prerequisites#

Configure database#

To avoid unnecessary memory usage, it is recommended to disable QuestDB's SELECT query cache by setting the property pg.select.cache.enabled=true in your server.conf. That's because Grafana does not use prepared statements when sending the queries and the query cache becomes much less efficient.

Add a data source#

  1. Open Grafana's UI (by default available at http://localhost:3000)
  2. Go to the Configuration section and click on Data sources
  3. Click Add data source
  4. Choose the PostgreSQL plugin and configure it with the following settings:
host: localhost:8812
database: qdb
user: admin
password: quest
SSL mode: disable
  1. When adding a panel, use the "text edit mode" by clicking the pencil icon and adding a query

Global variables#

To simplify queries which have dynamic elements such as date range filters, the query can contain global variables which are documented in the Grafana reference documentation.

$__timeFilter(timestamp)#

This variable allows filtering results by sending a start-time and end-time to QuestDB. This expression evaluates to:

timestamp BETWEEN
'2018-02-01T00:00:00Z' AND '2018-02-28T23:59:59Z'

$__interval#

This variable calculates a dynamic interval based on the time range applied to the dashboard. By using this function, the sampling interval changes automatically as the user zooms in and out of the panel.

Example query#

SELECT
pickup_datetime AS time,
avg(trip_distance) AS distance
FROM taxi_trips
WHERE $__timeFilter(pickup_datetime)
SAMPLE BY $__interval;