HTTP Streaming

Set Up a Summary Table for Data Ingested via HTTP Streaming

To configure a summary table, complete the following steps:

1. Define summary transform.
2. Create summary table.

Define Summary Transform

The summary transform defines a SQL statement that aggregates your data over some period of time.

The following example shows a general form for summary transforms:

SELECT
   <time_field_aggregation> AS <alias>,
   <function_on_column> AS <alias>,
   .......
FROM
    <parent_project.parent_table>
GROUP BY 
        <time_field_alias>
SETTINGS 
        hdx_primary_key = '<time_field_alias>'

Summary transforms are subject to the following limitations:

• In the SETTINGS clause, you must specify a hdx_primary_key. This primary key should correspond to a time field aggregation alias in your SELECT statement.
• In the FROM clause, specify the project name and the table name of the parent table.

📘

Test Summary Transform

To test your summary transform, run it without the SETTINGS clause on the parent table.

Example

Consider a summary table that aggregates, on an hourly basis:

• the sum of item cost
• the average tax
• the 95th percentile of my.journeys

The following SQL shows how you could translate these requirements into a summary transform:

select
    toStartOfHour(timestamp) as hour,
    sum(cost) as sumcost,
    avg(tax) as avgtax,
    quantile(.95)(distance['local']) as _95th
from
    my.journeys
group by
    hour 
SETTINGS hdx_primary_key = 'hour'

Create Summary Table

The summary table persists the aggregation results generated by your summary transform. You can create your summary table with the Hydrolix UI or the API.

To create a table with the Hydrolix API, see the API Reference.

To create a table with the Hydrolix UI, follow these instructions:

1. In the top right of the portal, click the "+ Add New" button.
2. From the options in the right sidebar, select "Table".
3. Specify the following:
   • a project where you wish to place the table
   • a table name
   • a description for the table
4. Click on "Advanced Settings".
5. Check the "Enable Summary" checkbox.
6. In the "Summary sql" field, paste the summary transform you defined above. Don't forget the SETTINGS clause!
7. Click "Save Changes" to save your advanced options.
8. Click "Save table" to create your table.