1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96
// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
//! Data source traits
use std::any::Any;
use std::sync::Arc;
use async_trait::async_trait;
use crate::arrow::datatypes::SchemaRef;
use crate::error::Result;
use crate::logical_plan::Expr;
use crate::physical_plan::ExecutionPlan;
/// Indicates whether and how a filter expression can be handled by a
/// TableProvider for table scans.
#[derive(Debug, Clone, PartialEq)]
pub enum TableProviderFilterPushDown {
/// The expression cannot be used by the provider.
Unsupported,
/// The expression can be used to help minimise the data retrieved,
/// but the provider cannot guarantee that all returned tuples
/// satisfy the filter. The Filter plan node containing this expression
/// will be preserved.
Inexact,
/// The provider guarantees that all returned data satisfies this
/// filter expression. The Filter plan node containing this expression
/// will be removed.
Exact,
}
/// Indicates the type of this table for metadata/catalog purposes.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum TableType {
/// An ordinary physical table.
Base,
/// A non-materialised table that itself uses a query internally to provide data.
View,
/// A transient table.
Temporary,
}
/// Source table
#[async_trait]
pub trait TableProvider: Sync + Send {
/// Returns the table provider as [`Any`](std::any::Any) so that it can be
/// downcast to a specific implementation.
fn as_any(&self) -> &dyn Any;
/// Get a reference to the schema for this table
fn schema(&self) -> SchemaRef;
/// Get the type of this table for metadata/catalog purposes.
fn table_type(&self) -> TableType {
TableType::Base
}
/// Create an ExecutionPlan that will scan the table.
/// The table provider will be usually responsible of grouping
/// the source data into partitions that can be efficiently
/// parallelized or distributed.
async fn scan(
&self,
projection: &Option<Vec<usize>>,
filters: &[Expr],
// limit can be used to reduce the amount scanned
// from the datasource as a performance optimization.
// If set, it contains the amount of rows needed by the `LogicalPlan`,
// The datasource should return *at least* this number of rows if available.
limit: Option<usize>,
) -> Result<Arc<dyn ExecutionPlan>>;
/// Tests whether the table provider can make use of a filter expression
/// to optimise data retrieval.
fn supports_filter_pushdown(
&self,
_filter: &Expr,
) -> Result<TableProviderFilterPushDown> {
Ok(TableProviderFilterPushDown::Unsupported)
}
}