Trait TableSource

pub trait TableSource: Sync + Send {
    // Required methods
    fn as_any(&self) -> &(dyn Any + 'static);
    fn schema(&self) -> Arc<Schema>;

    // Provided methods
    fn constraints(&self) -> Option<&Constraints> { ... }
    fn table_type(&self) -> TableType { ... }
    fn supports_filters_pushdown(
        &self,
        filters: &[&Expr],
    ) -> Result<Vec<TableProviderFilterPushDown>, DataFusionError> { ... }
    fn get_logical_plan(&self) -> Option<Cow<'_, LogicalPlan>> { ... }
    fn get_column_default(&self, _column: &str) -> Option<&Expr> { ... }
}

Access schema information and filter push-down capabilities.

The TableSource trait is used during logical query planning and optimizations and provides a subset of the functionality of the TableProvider trait in the (core) datafusion crate. The TableProvider trait provides additional capabilities needed for physical query execution (such as the ability to perform a scan).

The reason for having two separate traits is to avoid having the logical plan code be dependent on the DataFusion execution engine. Some projects use DataFusion’s logical plans and have their own execution engine.

Required Methods

fn as_any(&self) -> &(dyn Any + 'static)

fn schema(&self) -> Arc<Schema>

Get a reference to the schema for this table

Provided Methods

fn constraints(&self) -> Option<&Constraints>

Get primary key indices, if one exists.

fn table_type(&self) -> TableType

Get the type of this table for metadata/catalog purposes.

fn supports_filters_pushdown( &self, filters: &[&Expr], ) -> Result<Vec<TableProviderFilterPushDown>, DataFusionError>

Tests whether the table provider can make use of any or all filter expressions to optimise data retrieval.

fn get_logical_plan(&self) -> Option<Cow<'_, LogicalPlan>>

Get the Logical plan of this table provider, if available.

fn get_column_default(&self, _column: &str) -> Option<&Expr>

Get the default value for a column, if available.

Implementations on Foreign Types

impl TableSource for DefaultTableSource

fn as_any(&self) -> &(dyn Any + 'static)

Returns the table source as Any so that it can be downcast to a specific implementation.

fn schema(&self) -> Arc<Schema>

Get a reference to the schema for this table

fn constraints(&self) -> Option<&Constraints>

Get a reference to applicable constraints, if any exists.

fn supports_filters_pushdown( &self, filter: &[&Expr], ) -> Result<Vec<TableProviderFilterPushDown>, DataFusionError>

Tests whether the table provider can make use of any or all filter expressions to optimise data retrieval.

fn get_logical_plan(&self) -> Option<Cow<'_, LogicalPlan>>

fn get_column_default(&self, column: &str) -> Option<&Expr>

Implementors

impl TableSource for SqlTableSource

Implement TableSource, used in the logical query plan and in logical query optimizations

impl TableSource for LogicalTableSource