Datasets QuestDB Example

Read, downsample, and write QuestDB time-series data from a Dataset.

How-to Guides → Solution Examples → Feature Examples → Business Operations Examples → Datasets QuestDB Example

Summary

This example walks through three time-series operations against a QuestDB table from a FrameworX solution: a basic latest-rows read, a server-side downsampling query using QuestDB's SAMPLE BY stage, and a row insert through a Dataset Table. The work is done entirely from FrameworX, using the existing PostgreSQL Dataset Provider with one mandatory connection-string flag.

For other surfaces of the QuestDB connector (Device Protocol, UNS TagProvider, Historian StorageLocation), see the QuestDB Time-Series Database Connector reference page. For high-volume time-series appends at runtime, the Historian StorageLocation surface using ILP/HTTP is the recommended write path; this example uses a Dataset Table insert for demonstration parity with the MongoDB Datasets example.

Technical Information

The example creates one Dataset DB connection, three Queries, one Table, three Script Tasks, and a small set of UNS Tags. Each piece is configured in the Designer.

Configure the Dataset DB

In Datasets / DBs, create a connection:

• Name: questdb_local
• Provider: PostgreSQL
• Connection String:

  Server=localhost;Port=8812;Database=qdb;Username=admin;Password=quest;Server Compatibility Mode=NoTypeLoading;

The Server Compatibility Mode=NoTypeLoading flag is required. Without it, the Npgsql client tries to load PostgreSQL system catalog tables that QuestDB does not expose, and the connection fails. Click Test to verify the connection works against the running QuestDB server.

Configure the Queries

In Datasets / Queries, create three queries against the questdb_local connection. All three are native QuestDB SQL.

QueryLatestReadings. Returns the latest 10 readings for Plant01.

SELECT timestamp, plant, temperature, quality
FROM sensors
WHERE plant = 'Plant01'
ORDER BY timestamp DESC
LIMIT 10

QuerySampleByHourly. Server-side hourly downsampling of temperature readings for Plant01, using QuestDB's signature SAMPLE BY stage. The aggregation runs inside QuestDB - the FrameworX runtime receives one row per hour bucket, not raw samples.

SELECT timestamp, avg(temperature) avg_temp, min(temperature) min_temp, max(temperature) max_temp
FROM sensors
WHERE plant = 'Plant01'
SAMPLE BY 1h FILL(NULL)
ORDER BY timestamp DESC
LIMIT 24

QueryCountGoodQuality. Counts samples whose quality field is Good (FrameworX quality code 192).

SELECT count() AS good_count
FROM sensors
WHERE quality = 192

Configure the Dataset Table

In Datasets / Tables, create one table named TableSensors bound to the sensors table on the questdb_local connection. The Dataset Table primary key is the designated timestamp column. AddRow() + Save() dispatches an INSERT over the PostgreSQL wire to QuestDB. For high-volume telemetry appends at runtime, configure the Historian StorageLocation surface instead - it routes through ILP/HTTP and is optimized for batched append.

Configure the UNS Tags

In Unified Namespace / Tags, create the tags used by the tasks:

• QueryResult. Receives the output of the Latest and SampleBy queries.
• GoodSampleCount. Receives the result of the Count query.
• TriggerLatest, TriggerSampleBy, TriggerInsert. Script task triggers.
• LatestPlantCode, LatestTemperature. Values written back to QuestDB by the Insert task.

Configure the Script Tasks

In Scripts / Tasks, create three tasks, each triggered by the matching trigger tag.

Latest task.

@Tag.QueryResult = @Dataset.Query.QueryLatestReadings.SelectCommand();
@Info.Trace("Latest OK: " + @Tag.QueryResult);

SampleBy task.

@Tag.QueryResult = @Dataset.Query.QuerySampleByHourly.SelectCommand();
@Info.Trace("SampleBy OK: " + @Tag.QueryResult);

Insert task (via the Dataset Table).

@Dataset.Table.TableSensors.AddRow();
@Dataset.Table.TableSensors.Row["plant"] = @Tag.LatestPlantCode;
@Dataset.Table.TableSensors.Row["temperature"] = @Tag.LatestTemperature;
@Dataset.Table.TableSensors.Row["quality"] = (short)192;
@Dataset.Table.TableSensors.Row["timestamp"] = DateTime.UtcNow;
int i = @Dataset.Table.TableSensors.Save();
@Info.Trace("Insert OK: " + i);

Run the example

After you finish the configuration and create the scripts, run the solution and trigger each task. Values arrive in the QuestDB sensors table and the Latest and SampleBy results populate the QueryResult tag. The Count query populates GoodSampleCount. Trace output appears in the runtime log.

QuestDB time-series extensions

The PostgreSQL Dataset Provider passes native QuestDB SQL through unchanged. Beyond SAMPLE BY shown above, QuestDB exposes several time-series-specific features that work directly from a Dataset Query:

• LATEST ON - returns the most recent row per group. Example: SELECT * FROM sensors LATEST ON timestamp PARTITION BY plant; returns the latest reading for each plant.
• ASOF JOIN - time-series alignment with optional TOLERANCE. Joins two tables on the closest preceding timestamp.
• Materialized views - persisted aggregations refreshed on a calendar or interval. Read them from a Dataset Query the same way you read a regular table.
• Array types - QuestDB supports N-dimensional arrays for AI and financial workloads. Returned as native arrays through the PostgreSQL wire protocol.

Caveats

• Cursor support is forward-only. Scrollable cursors (DECLARE CURSOR ... SCROLL) are not available.
• QuestDB transaction semantics differ from standard PostgreSQL. Single-statement implicit transactions are the default.
• PostgreSQL extensions (PostGIS, pg_stat_statements, etc.) are not available - QuestDB exposes only the wire protocol, not the full PostgreSQL ecosystem.
• For high-volume time-series appends at runtime, prefer the Historian StorageLocation surface (ILP/HTTP) over Dataset Table inserts (PostgreSQL wire). See the QuestDB Time-Series Database Connector reference page for the Historian StorageLocation configuration.

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