Selection and Ordering

Columns

The columns property specifies which columns should be included in the View’s output. This allows users to show or hide a specific subset of columns, as well as control the order in which columns appear to the user. This is represented in Perspective as an array of string column names:

const view = await table.view({
    columns: ["a"],
});

view = table.view(columns=["a"])

#![allow(unused)]
fn main() {
let view = table.view(Some(ViewConfigUpdate {
    columns: Some(vec![Some("a".into())]),
    ..ViewConfigUpdate::default()
})).await?;
}

Sort

The sort property specifies columns on which the query should be sorted, analogous to ORDER BY in SQL. A column can be sorted regardless of its data type, and sorts can be applied in ascending or descending order. Perspective represents sort as an array of arrays, with the values of each inner array being a string column name and a string sort direction. When split_by are applied, the additional sort directions "col asc" and "col desc" will determine the order of pivot column groups.

const view = await table.view({
    sort: [["a", "asc"]],
});

view = table.view(sort=[["a", "asc"]])

#![allow(unused)]
fn main() {
let view = table.view(Some(ViewConfigUpdate {
    sort: Some(vec![Sort("a".into(), SortDir::Asc)]),
    ..ViewConfigUpdate::default()
})).await?;
}

The available sort directions are:

Filter

The filter property specifies columns on which the query can be filtered, returning rows that pass the specified filter condition. This is analogous to the WHERE clause in SQL. There is no limit on the number of columns where filter is applied, but the resulting dataset is one that passes all the filter conditions, i.e. the filters are joined with an AND condition. The join condition can be changed to OR via the filter_op property.

Perspective represents filter as an array of arrays, with the values of each inner array being a string column name, a string filter operator, and a filter operand in the type of the column:

const view = await table.view({
    filter: [["a", "<", 100]],
});

view = table.view(filter=[["a", "<", 100]])

#![allow(unused)]
fn main() {
let view = table.view(Some(ViewConfigUpdate {
    filter: Some(vec![Filter::new("a", "<", FilterTerm::Scalar(Scalar::Float(100.0)))]),
    ..ViewConfigUpdate::default()
})).await?;
}

The available filter operators depend on the column type:

String columns: ==, !=, >, >=, <, <=, begins with, contains, ends with, in, not in, is not null, is null.

Numeric columns (integer, float): ==, !=, >, >=, <, <=, is not null, is null.

Boolean columns: ==, is not null, is null.

Date/Datetime columns: ==, !=, >, >=, <, <=, is not null, is null.