First not null (nnfirst)
Returns the first non-null value found in a specified column for each grouping occurrence. To determine the first value, Devo uses the eventdate time rather than the log time, that is, the date Devo receives it rather than the date it was generated.
If you want to include null values, you can use the First (first) operation.
How does it work in the search window?
Before being able to perform this operation, you have to group your data. Be aware that the columns used as arguments for the grouping operation will not be available to select as arguments for the aggregation operation.
After grouping the data, select Aggregation in the search window toolbar, then select the First not null operation. You need to specify one argument:
|First of (mandatory)||Any|
The data type of the aggregated values will be the same as the data type of the column used as an argument.
demo.ecommerce.data table, we want to get the first non-null IP address value in each 5-minute period. Before aggregating the data, the table must be grouped in 5-minute intervals. Then we will perform the aggregation using the First not null operation.
The arguments needed for the First not null operation are:
- First of → clientIpAddress column
Click Aggregate function and you will see the following result:
How does it work in LINQ?
Group your data using the following structure:
as... to add the new column that will show the aggregated values. This is the syntax for the First not null operation:
See Build a query using LINQ to learn more about grouping and aggregating your data using the LINQ language.
You can copy the following LINQ syntax and try the example above on the
from demo.ecommerce.data group every 5m every 5m select nnfirst(clientIpAddress) as first_nonnull_IP