Struct View

pub struct View(/* private fields */);

The View struct is Perspective’s query and serialization interface. It represents a query on the Table’s dataset and is always created from an existing Table instance via the Table::view method.

Views are immutable with respect to the arguments provided to the Table::view method; to change these parameters, you must create a new View on the same Table. However, each View is live with respect to the Table’s data, and will (within a conflation window) update with the latest state as its parent Table updates, including incrementally recalculating all aggregates, pivots, filters, etc. View query parameters are composable, in that each parameter works independently and in conjunction with each other, and there is no limit to the number of pivots, filters, etc. which can be applied.

To construct a View, call the Table::view factory method. A Table can have as many Views associated with it as you need - Perspective conserves memory by relying on a single Table to power multiple Views concurrently.

Implementations

impl View

pub fn column_paths(&self, py: Python<'_>) -> PyResult<Vec<String>>

Returns an array of strings containing the column paths of the View without any of the source columns.

A column path shows the columns that a given cell belongs to after pivots are applied.

pub fn to_columns_string( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<String>

Renders this View as a column-oriented JSON string. Useful if you want to save additional round trip serialize/deserialize cycles.

pub fn to_json_string( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<String>

Renders this View as a row-oriented JSON string.

pub fn to_ndjson( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<String>

Renders this View as an NDJSON formatted String.

pub fn to_records<'a>( &self, py: Python<'a>, window: Option<Py<PyDict>>, ) -> PyResult<Bound<'a, PyAny>>

Renders this View as a row-oriented Python list.

pub fn to_json<'a>( &self, py: Python<'a>, window: Option<Py<PyDict>>, ) -> PyResult<Bound<'a, PyAny>>

Renders this View as a row-oriented Python list.

pub fn to_columns<'a>( &self, py: Python<'a>, window: Option<Py<PyDict>>, ) -> PyResult<Bound<'a, PyAny>>

Renders this View as a column-oriented Python dict.

pub fn to_csv( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<String>

Renders this View as a CSV String in a standard format.

pub fn to_dataframe( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<Py<PyAny>>

Renders this View as a pandas.DataFrame.

pub fn to_pandas( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<Py<PyAny>>

Renders this View as a pandas.DataFrame.

pub fn to_polars( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<Py<PyAny>>

Renders this View as a polars.DataFrame.

pub fn to_arrow( &self, py: Python<'_>, window: Option<Py<PyDict>>, ) -> PyResult<Py<PyBytes>>

Renders this View as the Apache Arrow data format.

Arguments

• window - a [ViewWindow]

pub fn delete(&self, py: Python<'_>) -> PyResult<()>

Delete this View and clean up all resources associated with it. View objects do not stop consuming resources or processing updates when they are garbage collected - you must call this method to reclaim these.

pub fn expand(&self, py: Python<'_>, index: u32) -> PyResult<u32>

pub fn collapse(&self, py: Python<'_>, index: u32) -> PyResult<u32>

pub fn dimensions(&self, py: Python<'_>) -> PyResult<Py<PyAny>>

Returns this View’s dimensions, row and column count, as well as those of the crate::Table from which it was derived.

• num_table_rows - The number of rows in the underlying crate::Table.
• num_table_columns - The number of columns in the underlying crate::Table (including the index column if this crate::Table was constructed with one).
• num_view_rows - The number of rows in this View. If this View has a group_by clause, num_view_rows will also include aggregated rows.
• num_view_columns - The number of columns in this View. If this View has a split_by clause, num_view_columns will include all column paths, e.g. the number of columns clause times the number of split_by groups.

pub fn expression_schema( &self, py: Python<'_>, ) -> PyResult<HashMap<String, String>>

The expression schema of this View, which contains only the expressions created on this View. See View::schema for details.

pub fn get_config(&self, py: Python<'_>) -> PyResult<Py<PyAny>>

A copy of the [ViewConfig] object passed to the Table::view method which created this View.

pub fn get_min_max( &self, py: Python<'_>, column_name: String, ) -> PyResult<(String, String)>

Calculates the [min, max] of the leaf nodes of a column column_name.

Returns

A tuple of [min, max], whose types are column and aggregate dependent.

pub fn num_rows(&self, py: Python<'_>) -> PyResult<u32>

The number of aggregated rows in this View. This is affected by the “group_by” configuration parameter supplied to this view’s contructor.

Returns

The number of aggregated rows.

pub fn schema(&self, py: Python<'_>) -> PyResult<HashMap<String, String>>

The schema of this View.

The View schema differs from the schema returned by Table::schema; it may have different column names due to expressions or columns configs, or it maye have different column types due to the application og group_by and aggregates config. You can think of Table::schema as the input schema and View::schema as the output schema of a Perspective pipeline.

pub fn on_delete(&self, py: Python<'_>, callback: Py<PyAny>) -> PyResult<u32>

Register a callback with this View. Whenever the View is deleted, this callback will be invoked.

pub fn remove_delete(&self, py: Python<'_>, callback_id: u32) -> PyResult<()>

Unregister a previously registered View::on_delete callback.

pub fn on_update( &self, py: Python<'_>, callback: Py<PyAny>, mode: Option<String>, ) -> PyResult<u32>

Register a callback with this View. Whenever the view’s underlying table emits an update, this callback will be invoked with an object containing port_id, indicating which port the update fired on, and optionally delta, which is the new data that was updated for each cell or each row.

Arguments

• on_update - A callback function invoked on update, which receives an object with two keys: port_id, indicating which port the update was triggered on, and delta, whose value is dependent on the mode parameter.
• options - If this is provided as OnUpdateOptions { mode: Some(OnUpdateMode::Row) }, then delta is an Arrow of the updated rows. Otherwise delta will be Option::None.

pub fn remove_update(&self, py: Python<'_>, callback_id: u32) -> PyResult<()>

Unregister a previously registered update callback with this View.

Arguments

• id - A callback id as returned by a recipricol call to View::on_update.

Examples

let callback = |_| async { print!("Updated!") };
let cid = view.on_update(callback, OnUpdateOptions::default()).await?;
view.remove_update(cid).await?;

Trait Implementations

impl<'py> IntoPyObject<'py> for View

type Target = View

The Python output type

type Output = Bound<'py, <View as IntoPyObject<'py>>::Target>

The smart pointer type to use.

type Error = PyErr

The type returned in the event of a conversion error.

fn into_pyobject( self, py: Python<'py>, ) -> Result<<Self as IntoPyObject<'_>>::Output, <Self as IntoPyObject<'_>>::Error>

Performs the conversion.

impl PyClass for View

type Frozen = False

Whether the pyclass is frozen.

impl PyClassBaseType for View

type LayoutAsBase = PyClassObject<View>

type BaseNativeType = <View as PyClassImpl>::BaseNativeType

type Initializer = PyClassInitializer<View>

type PyClassMutability = <View as PyClassImpl>::PyClassMutability

impl PyClassImpl for View

const IS_BASETYPE: bool = true

#[pyclass(subclass)]

const IS_SUBCLASS: bool = false

#[pyclass(extends=…)]

const IS_MAPPING: bool = false

#[pyclass(mapping)]

const IS_SEQUENCE: bool = false

#[pyclass(sequence)]

const IS_IMMUTABLE_TYPE: bool = false

#[pyclass(immutable_type)]

type BaseType = PyAny

Base class

type ThreadChecker = SendablePyClass<View>

This handles following two situations:

type PyClassMutability = <<PyAny as PyClassBaseType>::PyClassMutability as PyClassMutability>::MutableChild

Immutable or mutable

type Dict = PyClassDummySlot

Specify this class has #[pyclass(dict)] or not.

type WeakRef = PyClassDummySlot

Specify this class has #[pyclass(weakref)] or not.

type BaseNativeType = PyAny

The closest native ancestor. This is PyAny by default, and when you declare #[pyclass(extends=PyDict)], it’s PyDict.

fn items_iter() -> PyClassItemsIter

fn doc(py: Python<'_>) -> PyResult<&'static CStr>

Rendered class doc

fn lazy_type_object() -> &'static LazyTypeObject<Self>

fn dict_offset() -> Option<isize>

fn weaklist_offset() -> Option<isize>

impl PyClassNewTextSignature<View> for PyClassImplCollector<View>

fn new_text_signature(self) -> Option<&'static str>

impl<'a, 'py> PyFunctionArgument<'a, 'py, false> for &'a View

type Holder = Option<PyRef<'py, View>>

fn extract( obj: &'a Bound<'py, PyAny>, holder: &'a mut Self::Holder, ) -> PyResult<Self>

impl<'a, 'py> PyFunctionArgument<'a, 'py, false> for &'a mut View

type Holder = Option<PyRefMut<'py, View>>

fn extract( obj: &'a Bound<'py, PyAny>, holder: &'a mut Self::Holder, ) -> PyResult<Self>

impl PyMethods<View> for PyClassImplCollector<View>

fn py_methods(self) -> &'static PyClassItems

impl PyTypeInfo for View

const NAME: &'static str = "View"

Class name.

const MODULE: Option<&'static str>

Module name, if any.

fn type_object_raw(py: Python<'_>) -> *mut PyTypeObject

Returns the PyTypeObject instance for this type.

fn type_object(py: Python<'_>) -> Bound<'_, PyType>

Returns the safe abstraction over the type object.

fn is_type_of(object: &Bound<'_, PyAny>) -> bool

Checks if object is an instance of this type or a subclass of this type.

fn is_exact_type_of(object: &Bound<'_, PyAny>) -> bool

Checks if object is an instance of this type.

impl DerefToPyAny for View