Trait TableSource

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pub trait TableSource: Sync + Send {
    // Required methods
    fn as_any(&self) -> &dyn Any;
    fn schema(&self) -> SchemaRef;

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

Expand description

Planning time information about a table.

This trait is used during logical query planning and optimizations, and provides a subset of the TableProvider trait, such as schema information and filter push-down capabilities. The TableProvider trait provides additional information needed for physical query execution, such as the ability to perform a scan or insert data.

§See Also:

DefaultTableSource to go from TableProvider, to TableSource

§Rationale

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§

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fn as_any(&self) -> &dyn Any

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fn schema(&self) -> SchemaRef

Get a reference to the schema for this table

Provided Methods§

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

Get primary key indices, if any

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fn table_type(&self) -> TableType

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

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

Tests whether the table provider can make use of any or all filter expressions to optimize data retrieval. Only non-volatile expressions are passed to this function.

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