3.1 Data Types

EventQL supports a number of SQL data types in several categories: numeric types, date and time types and string types. This page provides an overview of these data types and a summary of the data type storage requirements.

Data Types

Repeated Fields

EventQL schemas allow for a type to be specified as repeated. A repeated field can be repeated any number of times (including zero) in a well-formed row. The order of the repeated values will be preserved.

Let's look at a simple example:

CREATE TABLE ev.temperature_measurements (
  collected_at    DATETIME,
  sensor_id       STRING,
  measured_values REPEATED STRING,
  PRIMARY KEY(collected_at, sensor_id)
);

And an example JSON message that is valid for the above schema:

{
  "collected_at": "2016-07-05 13:34:51",
  "sensor_id": "sensor1",
  "measured_values": [ "A", "B", "C"]
}

The RECORD Type

The record type allows you to define nesting within a column. Its most useful in combination with repeated fields as this allows you to build schemas that can properly represent arbitrary JSON objects.

We can modify our example above to include a location with each measure value:

CREATE TABLE ev.temperature_measurements (
  collected_at DATETIME,
  sensor_id    STRING,
  measurements REPEATED RECORD (
    thing_id     STRING,
    temperature  DOUBLE
  ),
  PRIMARY KEY(collected_at, sensor_id)
);

This JSON message can now be stored:

{
  "collected_at": "2016-07-05 13:34:51",
  "sensor_id": "sensor1",
  "measured_values": [
    { "thing_id": "thing1", temperature: 22.3 },
    { "thing_id": "thing2", temperature: 21.8 },
    { "thing_id": "thing3", temperature: 24.5 },
  ]
}