Filters

Rows are filtered using the filter operator. In the operator definition you write filter by followed by a single expression. The expression is evaluated on incoming rows, and rows are passed through if the expression evaluates to true, otherwise they are ignored.

Expressions are composed of constants, column identifiers, operators and functions. Any built-in function can be used, and you can also create your own functions using WebAssembly.

For an in-depth explanation of the expression language please see the section on expressions. To learn more about creating custom WebAssembly functions please see the section on WebAssembly

Here are some examples:

Extract UK sales into a new stream

uk_sales := sales -> (filter by country == "UK") -> (store stream)

Filter using a custom WebAssembly function fraud_score

fraudulent_tx := tx -> (filter by fraud_score(name, age, price, product_id) > 75) -> (store stream)